1978 GMC K25 Transmission Parts

Below you will find various in-demand GMC Transmission Parts, components and accessories for your 1978 K25. Advance Auto Parts has popular K25 parts like Transmission Cooler and Parts, Transmission Bearings, Transmission Mounts and more. You’ll also find aftermarket and OEM Transmission Parts for other K25 model years including 1975, 1976, 1977 and more. Select a category of 1978 GMC K25 Transmission Parts below and start saving instantly.

Please Select your Vehicle to See Exact Fit Parts

Popular 1978 GMC K25 Transmission Parts Categories

Gear Shift Levers

Transmission Torque Converters

OE Transmission Coolers

Transfer Shaft Bearing

Manual Transmission Differential Bearings

Transmission Solenoids

Transmission Oil Cooler Lines

Transmission Shift Cables

Countershaft Bearings

Manual Transmission Output Shaft Bearings

Back Up Lamp Switches

Transmission Pan Gaskets

Transmission Oil Cooler Fittings

Automatic Transmission Line Connectors

Transmission Mounts

Transmission Oil Pans

Transmission Master Repair Kits

Transmission Rebuild Kits

Transmission Oil Pan Gaskets

Transmission Dipsticks

Automatic Transmission Differential Bearings

Transmission Bushings

Detent Cables

Automatic Transmission Output Shaft Seals

Automatic Transmission Oil Pump Seals

Transmission Modulator Valves

Pinion Seals

Automatic Transmission Dipstick Seals

Transmission Seals and O-rings

Manual Transmission Bearing and Seal Overhaul Kits

Torque Converter Seals

Extension Housing Seals

Shaft Seals

Manual Transmission Gasket Sets

Gear Shift Lever Bushing

Transmission Shift Kits

Transmission Bands

Automatic Transmission Selector Shaft Seals

Automatic Transmission Flexplate Mounting Bolts

Automatic Transmission Output Shaft Bearings

Automatic Transmission Detent Cable Seals

Shift Shaft Seals

Automatic Transmission Oil Pump Gaskets

Automatic Transmission Fluid Filler Tube Seals

Manual Transmission Seals

Automatic Transmission Oil Pump O-Rings

Automatic Transmission Speedometer Pinion Seals

Automatic Transmission Seals

Automatic Transmission Shifter Cable Brackets

Automatic Transmission Friction Discs

Intermediate Shaft Bearings

Trans Mount Bushing

Automatic Transmission Kickdown Cables

Manual Transmission Bearing

Manual Transmission Seal Kit

Auto Trans Differential Bearing and Race Set

Essential Transmission Parts for 1978 GMC K25s

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$9.59

AT OIL PUMP ORING

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$118.99

AT CONTR SOLENOID

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$292.99

Add fluid capacity to your transmission. Extra fluid means more cooling, and more cooling means better efficiency and performance. Add life to your transmission with a B&M Deep Pan! Adds 2 additional quarts to the system.

Product Features:

Additional Oil Capacity
More Cooling Ability
No Dipstick Modification
Some Include Fluid Pickup Extension
Built-In Drain Plugs

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$33.99

Cable Bracket, GM APPLICATION: For TH400, 350, 250, 200, 700R4, 2004R transmissions.

Product Features:

Shifter Service Parts

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$25.99

Our products are engineered and tested to provide years of trouble free operation. Backed by over 50 years of mobile a/c experience, fix it once and fix it right with Imperial.

Product Features:

Transmission cooler reinstallation kit
Contains part numbers 248001, 226201, 240250 and 4 hose clamps
Provides all hardware for reinstallation of Imperial transmission coolers
Contains nylon mounting rods, foam pads, locking buttons, hose and fitting
Made of high grade nylon for easy installation
Removable buttons for cooler/fan relocation
Made for both transmission coolers and electric fan installation
Comes with Quick Connect coupler

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$136.99

Additional Oil Capacity
More Cooling Ability
No Dipstick Modification
Some Include Fluid Pickup Extension
Built-In Drain Plugs
Chrome Plated Steel

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$14.29

AT EXT HOUSING SEAL

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$23.99

Detent cables connect the throttle mechanism to the transmission. Old cables can bind, break, or just become sluggish. The best repair is to replace the old cable with a new one. ATP Detent cables are designed to fit And function just like the original part to ensure durability And long life.

Product Features:

Includes brackets, grommets, etc to match original
Helps transmission determine ideal downshift
Improves vehicle performance

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$5.19

Our wheel seals are engineered using only the highest-quality materials to meet vehicle manufacturer specificatons. We work with suppliers to design seals that meet FAG’s quality standards. Seals are designed to protect wheel end components from contamination – such as dirt, dust, and moisture – and prevent the loss of grease over the life of the bearing. The specifications for wheel seals are very demanding, and the type required depends on the specific application, position and vehicle class.

Product Features:

High-precision and High-quality components used in all KITs
Coverage of classic and new high-tech solutions for the best system coverage

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$29.99

AUTO TRANS BAND

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$9.59

AT CLUTCH PLATE

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$6.99

Product Features:

Design type: springless; single-lip
Temperature range: -40 Deg. F to 225 Deg. F / -40 Deg. C to 107 Deg. C
Good low temperature capability
Low swell in hydrocarbon fluids
Delivers quality and reliable performance for every type of repair

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$23.99

Flywheel and flex plate bolts play an important role in the performance and safety of race cars and street machines alike. That is why the fastener experts at ARP have developed special bolts that are far superior to OEM hardware. ARP offers two styles of flywheel/flex plate bolts: High Performance and Pro Series. They are both forged from aerospace alloy and heat treated prior to thread rolling and machining. Both feature an exclusive, flat, 12 point head design and larger than stock shank diameter for increased strength and improved flywheel register. The popular High Performance series is rated at 180,000 PSI, and the premium grade Pro Series, originally developed for NASCAR competition, has a 200,000 PSI rating. Complete with washers and nuts where applicable.

Product Features:

Forged From Aerospace Alloy And Heat Treated Prior To Thread Rolling And Machining
Feature An Exclusive, Flat, 12 Point Head Design And Larger Than Stock Shank Diameter
Flanged Nut
Increased Strength And Improved Flywheel Register
Chevy 90░ V6 & 305-502 With 1-pc Rear Seal
0.725″ Underhead Length
200,000 PSI

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$35.99

Product Features:

CONSISTENT PERFORMANCE: Matched cup and cone components ensure consistent performance
PREMIUM MATERIALS: Precision manufactured using premium-grade steel for outstanding durability and performance
SMOOTH ROTATION: Crowned raceways and rollers for even load distribution
OE-STYLE DESIGN: Engineered to meet OE specifications
COMPREHENSIVE COVERAGE: Industry-leading coverage for domestic and import applications
RIGOROUS TESTING: Comprehensive testing throughout design and development processes by National engineers for quality you can count on

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$393.99

AT MSTR REP KIT PLUS

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$8.99

National has built a reputation as one of the most respected names in the industry. We have offered premium sealing solutions for more than 75 years. Our design team keeps pace with the industry and provides advanced solutions for today’s vehicles.

Product Features:

Design type: springless; multi-lip
Temperature range: -40 Deg. F to 225 Deg. F / -40 Deg. C to 107 Deg. C
Good low temperature capability
Low swell in hydrocarbon fluids
Delivers quality and reliable performance for every type of repair

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$11.99

Our products are engineered and tested to provide years of trouble free operation. Backed by over 50 years of mobile a/c experience, fix it once and fix it right with Imperial.

Product Features:

Imperial mounting kit system
For installation of transmission coolers and electric fans
Provides quick, effective installation of Imperial products
Contains nylon mounting rods, foam pads and locking buttons
Aftermarket electric fan and cooler mounting rods
Made with the highest quality materials
Quality machined for durability
Removable buttons for relocation
Aftermarket electric fan and cooler mounting rods
Made with the highest quality materials
Quality machined for durability
Removable buttons for relocation

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$10.99

Design type: spring loaded; single-lip
Temperature range: -20 Deg. F to 300 Deg. F / -29 Deg. C to 49 Deg. C
Resistance to EP lubricants
Low swell in hydrocarbon fluids
Delivers quality and reliable performance for every type of repair

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$12.99

Our products are engineered and tested to provide years of trouble free operation. Backed by over 50 years of mobile a/c experience, fix it once and fix it right with Imperial.

Product Features:

Transmission line fitting kit
GM, Jeep; 5/8″-18 inverted flare
Helps simplify transmission cooler installation
Allows for auxiliary transmission cooler installation without cutting OE lines
Crafted from high-quality material that makes it durable and longer-lasting
A high quality, direct fit OE replacement
Easily connects the transmission cooler line to the cooler hose
Coated for extra protection against corrosion
Crafted from high-quality material that makes it durable and longer-lasting
A high quality, direct fit OE replacement
Easily connects the transmission cooler line to the cooler hose
Coated for extra protection against corrosion

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$4.29

AT SOLENOID SEAL

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$99.99

These universal fit adjustable cables will work in 95 percent of all listed transmission applications, yet are less expensive than OE models. Use as straight replacement cable or ease the installation of transmission swaps.

Product Features:

Universal Fit Adjustable
Less Expensive Than OE Models
Ease Trans. Swap Installation

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$24.29

With advanced load-carrying capacity and compact design, tapered roller bearings are used in wheel bearings, transmissions, differentials, transfer cases and other miscellanous applications. FAG manufacturers over 100 million tapered roller bearings annually.

Product Features:

High-precision and High-quality components used in all KITs
Coverage of classic and new high-tech solutions for the best system coverage

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$60.99

Our products are engineered and tested to provide years of trouble free operation. Backed by over 50 years of mobile a/c experience, fix it once and fix it right with Imperial.

Product Features:

Imperial high-performance transmission cooler
Size: 3/4″ x 7-1/2″ x 12-1/2″
SAE 45-degree fittings for maximum reliability
Electrostatic powder-coated to prevent corrosion
SAE 45 degree fittings for maximum reliability
Electrostatically powder coated to prevent corrosion
All aluminum lightweight construction
SAE 45 degree fittings for maximum reliability
Electrostatically powder coated to prevent corrosion
All aluminum lightweight construction

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$27.49

Made from cork/neoprene gasket material which features excellent compressibility and high recovery to create a positive seal.

Product Features:

High density cork-nitrile rubber blend
Excellent compressibility and high recovery to create a positive seal
Excellent Compressibility

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$48.99

The transmission modulator valve is a vacuum operated mechanical device located on the transmission case. This valve will have a actuator rod extended into the transmission valve body inside the transmission which will control the flow of transmission fluid within the transmission to place the transmission in the most optimal forward gear selection.

Product Features:

Application matched component ensures the transmission gear position system can be returned to like new condition.
Product constructed to meet all design and operating characteristics as intended by the vehicle manufacturer.
This part will look and function just like the original unit being replaced.

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$33.99

Fully adjustable vacuum modulator to maintain accurate shift points.

Product Features:

Meets or exceeds OE specifications

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$716.99

Converter: Th350 28-3200 Stall

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$614.99

Nitrous Holeshot Converters are Built with the same features as the other B&M Holeshots, with the addition of anti-balloon plates. The anti-balloon plates will allow these converters to stand up to the instant horsepower nitrous delivers. Due to torque converter core availability, the actual converter size may vary but performance functionality will be as advertised.

Product Features:

2300-2500 RPM
Small And Big Blocks
Mild To Serious Performance
Furnace Brazed
Fully Balanced

Upgrade your 1978 GMC K25 with Top-Quality Transmission Parts

When it comes to maintaining or upgrading your 1978 GMC K25, nothing is more important than using high-quality OEM or aftermarket parts that you can trust. Whether you’re repairing damage to your GMC or enhancing its overall performance, Transmission Parts are key to keeping your K25 functioning at its best. At Advance Auto Parts, we offer a wide selection of 155 Transmission Parts for the 1978 GMC K25, designed to meet your needs without breaking the bank. From Transmission Cooler and Part replacements to Transmission Bearings upgrades, we’ve got you covered with parts that fit your vehicle perfectly and ensure long-lasting performance.

Affordable Prices and Wide Selection

Shopping for Transmission Parts for any vehicle can be a hassle, especially if you’re on a budget. But with Advance Auto Parts, you can find high-quality Transmission Parts for your 1978 GMC K25 at great prices. Our Transmission Parts inventory for this model ranges from just $3.19 to $1,349.99, with an average price of $148.54. Our 155 Transmission Parts in stock come from 21 trusted brands, so you’re sure to find the right part for your 1978 GMC K25 without overspending.

Top Brands and High Customer Satisfaction

Advance Auto Parts takes pride in offering only the best brands in the automotive industry. For your 1978 GMC K25, we stock popular OEM and aftermarket Transmission Parts from top names like National, B & M, Imperial, and more. National Transmission Parts start at just $8.99 and boast an impressive 4.3 stars average rating from customers. B & M and Imperial also bring quality to the table, with Transmission Parts available starting at $11.99, and at an average 4.1 stars rating. With 1,826 customer reviews and counting, our 1978 GMC K25 Transmission Parts have a strong track record of reliability, ensuring you can trust your purchase.

Explore Related Parts and More

While you’re here, don’t forget to check out other essential categories that go hand in hand with Transmission Part upgrades. Explore related part types like Batteries and Chargers, Oil and Lubricants and more to make sure your 1978 GMC K25 is always ready to roll. We’re committed to providing you with everything you need to keep your K25 in top shape, all in one place. Start shopping confidently below for your 1978 GMC K25!

Best-Selling Transmission Cooler and Parts for 1978 GMC K25s

Enhance the driving experience in your GMC with 14 quality Transmission Cooler and Part components, starting at $11.99.

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$85.99

Our products are engineered and tested to provide years of trouble free operation. Backed by over 50 years of mobile a/c experience, fix it once and fix it right with Imperial.

Product Features:

Imperial high-performance transmission cooler
Size: 3/4″ x 10″ x 15-7/8″
SAE 45-degree fittings for maximum reliability
Electrostatic powder-coated to prevent corrosion
SAE 45 degree fittings for maximum reliability
Electrostatically powder coated to prevent corrosion
All aluminum lightweight construction
SAE 45 degree fittings for maximum reliability
Electrostatically powder coated to prevent corrosion
All aluminum lightweight construction

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$73.99

The Imperial Maxi-Cool XL’s plate and fin design offer excellent cooling efficiency in a compact, space-efficient design.

Product Features:

Imperial Maxi-Cool plate and fin transmission cooler
Size: 3/4″ x 11″ x 7-1/2″
Mid-size and full-size cars, pickups
GVWR up to 20,000 lbs.; towing up to 2,500 lbs.
Compatible with OEM cooler systems
Made with the highest quality materials
100% pressure testing to 150 PSI for quality assurance
33% more efficient than a comparable tube and fin design

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$11.99

Our products are engineered and tested to provide years of trouble free operation. Backed by over 50 years of mobile a/c experience, fix it once and fix it right with Imperial.

Product Features:

Imperial mounting kit system
For installation of transmission coolers and electric fans
Provides quick, effective installation of Imperial products
Contains nylon mounting rods, foam pads and locking buttons
Aftermarket electric fan and cooler mounting rods
Made with the highest quality materials
Quality machined for durability
Removable buttons for relocation
Aftermarket electric fan and cooler mounting rods
Made with the highest quality materials
Quality machined for durability
Removable buttons for relocation

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$55.99

Our products are engineered and tested to provide years of trouble free operation. Backed by over 50 years of mobile a/c experience, fix it once and fix it right with Imperial.

Product Features:

Imperial Econo-Kool tube and fin transmission cooler
Size: 3/4″ x 5″ x 15-7/8″
Compact and mid-size cars
GVWR up to 16,000 lbs.; towing up to 2,500 lbs.
Compatible with OEM cooler systems
Ultrasonically soldered for reliability
100% pressure testing to 150 PSI for quality assurance
High efficiency turbulators
Compatible with OEM cooler systems
Ultrasonically soldered for reliability
100% pressure testing to 150 PSI for quality assurance
High efficiency turbulators

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$40.99

Our products are engineered and tested to provide years of trouble free operation. Backed by over 50 years of mobile a/c experience, fix it once and fix it right with Imperial.

Product Features:

Imperial Econo-Kool tube and fin transmission cooler
Size: 3/4″ x 5″ x 12-1/2″
Sub-compact to compact cars
GVWR up to 12,000 lbs.
Compatible with OEM cooler systems
Ultrasonically soldered for reliability
100% pressure testing to 150 PSI for quality assurance
High efficiency turbulators
Compatible with OEM cooler systems
Ultrasonically soldered for reliability
100% pressure testing to 150 PSI for quality assurance
High efficiency turbulators

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$85.99

The Imperial Maxi-Cool XL’s plate and fin design offer excellent cooling efficiency in a compact, space-efficient design.

Product Features:

Class “A” motor homes, large travel trailers, 5th-wheel trailers
GVWR up to 30,000 lbs.; towing up to 10,000 lbs.
Compatible with OEM cooler systems
33% more efficient than a comparable tube and fin design

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$65.99

Our products are engineered and tested to provide years of trouble free operation. Backed by over 50 years of mobile a/c experience, fix it once and fix it right with Imperial.

Product Features:

Imperial Econo-Kool tube and fin transmission cooler
Size: 3/4″ x 10″ x 15-7/8″
Class “A” motor homes, large travel trailers, 5th-wheel trailers
GVWR up to 26,000 lbs.; towing up to 10,000 lbs.
Compatible with OEM cooler systems
Ultrasonically soldered for reliability
100% pressure testing to 150 PSI for quality assurance
High efficiency turbulators
Compatible with OEM cooler systems
Ultrasonically soldered for reliability
100% pressure testing to 150 PSI for quality assurance
High efficiency turbulators

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$80.99

The Imperial Maxi-Cool XL’s plate and fin design offer excellent cooling efficiency in a compact, space-efficient design.

Product Features:

Imperial Rapid-Cool plate and fin transmission cooler
Size: 3/4″ x 11″ x 9-1/2″
Pickup trucks and vans, class “C” motor homes, travel trailers to 24′
GVWR up to 24,000 lbs.; towing up to 5,000 lbs.
33% more efficient than a comparable tube and fin design
Compatible with OEM cooler systems
Made with the highest quality materials
100% pressure testing to 150 PSI for quality assurance
33% more efficient than a comparable tube and fin design

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$52.99

Our products are engineered and tested to provide years of trouble free operation. Backed by over 50 years of mobile a/c experience, fix it once and fix it right with Imperial.

Product Features:

Mid-size and full-size cars, pickups
GVWR up to 18,000 lbs.; towing up to 3,500 lbs
Compatible with OEM cooler systems
Ultrasonically soldered for reliability
100% pressure testing to 150 PSI for quality assurance
High efficiency turbulators
Compatible with OEM cooler systems
Ultrasonically soldered for reliability
100% pressure testing to 150 PSI for quality assurance
High efficiency turbulators

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$79.99

Our products are engineered and tested to provide years of trouble free operation. Backed by over 50 years of mobile a/c experience, fix it once and fix it right with Imperial.

Product Features:

Imperial high-performance transmission cooler
Size: 3/4″ x 7-1/2″ x 15-7/8″
SAE 45-degree fittings for maximum reliability
Electrostatic powder-coated to prevent corrosion
Up to Class C motorhomes, towing up to 5,000 pounds
SAE 45 degree fittings for maximum reliability
Electrostatically powder coated to prevent corrosion
All aluminum lightweight construction

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$25.99

Our products are engineered and tested to provide years of trouble free operation. Backed by over 50 years of mobile a/c experience, fix it once and fix it right with Imperial.

Product Features:

Transmission cooler reinstallation kit
Contains part numbers 248001, 226201, 240250 and 4 hose clamps
Provides all hardware for reinstallation of Imperial transmission coolers
Contains nylon mounting rods, foam pads, locking buttons, hose and fitting
Made of high grade nylon for easy installation
Removable buttons for cooler/fan relocation
Made for both transmission coolers and electric fan installation
Comes with Quick Connect coupler

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$60.99

Our products are engineered and tested to provide years of trouble free operation. Backed by over 50 years of mobile a/c experience, fix it once and fix it right with Imperial.

Product Features:

Imperial high-performance transmission cooler
Size: 3/4″ x 7-1/2″ x 12-1/2″
SAE 45-degree fittings for maximum reliability
Electrostatic powder-coated to prevent corrosion
SAE 45 degree fittings for maximum reliability
Electrostatically powder coated to prevent corrosion
All aluminum lightweight construction
SAE 45 degree fittings for maximum reliability
Electrostatically powder coated to prevent corrosion
All aluminum lightweight construction

from

$65.99

Our products are engineered and tested to provide years of trouble free operation. Backed by over 50 years of mobile a/c experience, fix it once and fix it right with Imperial.

Product Features:

Imperial Econo-Kool tube and fin transmission cooler
Size: 3/4″ x 7-1/2″ x 15-7/8″
Pickup trucks and vans, class “C” motor homes, travel trailers to 24′
GVWR up to 22,000 lbs.; towing up to 5,000 lbs.
Compatible with OEM cooler systems
Ultrasonically soldered for reliability
100% pressure testing to 150 PSI for quality assurance
High efficiency turbulators
Compatible with OEM cooler systems
Ultrasonically soldered for reliability
100% pressure testing to 150 PSI for quality assurance
High efficiency turbulators

from

$151.99

Our products are engineered and tested to provide years of trouble free operation. Backed by over 50 years of mobile a/c experience, fix it once and fix it right with Imperial.

Product Features:

Imperial Econo-Kool tube and fin transmission cooler
Size: 1-1/2″ x 12″ x 15 1/8″
Severe-duty transmission oil cooling applications
Towing with class “A” motor home or towing more than 10,000 lbs.
Compatible with OEM cooler systems
Ultrasonically soldered for reliability
100% pressure testing to 150 PSI for quality assurance
High efficiency turbulators

Most Popular 1978 GMC K25 Transmission Bearings

Customize your GMC with 11 Transmission Bearings products like Countershaft Bearings, Automatic Transmission Differential Bearings, and Manual Transmission Output Shaft Bearings, all priced under $43.99.

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$8.99

Manufactured with premium-grade steel, National taper bearing cups feature crowned raceways to ensure even load distribution.

Product Features:

PREMIUM MATERIALS – Precision manufactured using premium-grade steel for outstanding durability and performance
SMOOTH ROTATION – Crowned raceways for even load distribution
OE-STYLE DESIGN – Engineered to meet OE specifications
COMPREHENSIVE COVERAGE – Industry-leading coverage for domestic and import applications
RIGOROUS TESTING – Comprehensive testing throughout design and development processes by National engineers for quality you can count on

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$15.99

Driveworks wheel bearings are a direct replacement for original parts at a much more affordable cost. Each wheel bearing is engineered to meet or exceed OE specifications, and goes through intensive quality control inspections to ensure proper fitment. Manufactured using high-precision machinery and advanced heat treatment processes, these bearings are designed for maximum durability and extended periods of use under any driving condition. Specific to certain applications, Driveworks bearings have multi-lip seals built into the bearing for increased protection against invasive contaminants and premature wear.

Product Features:

Depending on the application, specified Driveworks wheel bearings have integrated encoder rings that automatically sync with the vehicle’s anti-lock braking system (ABS) upon successful installation
Engineered, manufactured, and tested to meet or exceed OE specifications
Integrated seal design improves contamination resistance for a longer bearing life
High performance grease is used to lubricate the inner raceway to ensure smooth operation, higher operating temperatures, and minimal noise
Manufactured from high quality steel to maximize durability under even the harshest driving conditions
Brand may vary by location

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$21.99

Manufactured with premium-grade steel, National taper bearing cones feature crowned raceways and rollers to ensure even load distribution.

Product Features:

PREMIUM MATERIALS – Precision manufactured using premium-grade steel for outstanding durability and performance
SMOOTH ROTATION – Crowned raceways and rollers for even load distribution
OE-STYLE DESIGN – Engineered to meet OE specifications
COMPREHENSIVE COVERAGE – Industry-leading coverage for domestic and import applications
RIGOROUS TESTING – Comprehensive testing throughout design and development processes by National engineers for quality you can count on

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$10.99

Value-priced bearing meets all cataloged application requirements.

Product Features:

Brand may vary by location

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$27.99

Manufactured with premium-grade steel, National taper bearing cones feature crowned raceways and rollers to ensure even load distribution.

Product Features:

PREMIUM MATERIALS – Precision manufactured using premium-grade steel for outstanding durability and performance
SMOOTH ROTATION – Crowned raceways and rollers for even load distribution
OE-STYLE DESIGN – Engineered to meet OE specifications
COMPREHENSIVE COVERAGE – Industry-leading coverage for domestic and import applications
RIGOROUS TESTING – Comprehensive testing throughout design and development processes by National engineers for quality you can count on

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$7.99

Value-priced bearing meets all cataloged application requirements.

Product Features:

Brand may vary by location

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$12.99

Manufactured with premium-grade steel, National taper bearing cups feature crowned raceways to ensure even load distribution.

Product Features:

PREMIUM MATERIALS – Precision manufactured using premium-grade steel for outstanding durability and performance
SMOOTH ROTATION – Crowned raceways for even load distribution
OE-STYLE DESIGN – Engineered to meet OE specifications
COMPREHENSIVE COVERAGE – Industry-leading coverage for domestic and import applications
RIGOROUS TESTING – Comprehensive testing throughout design and development processes by National engineers for quality you can count on

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$43.99

We develop and produce high-quality roller bearings, spherical bearings, and plain bearings worldwide for a wide range of applications.

Product Features:

High-precision and High-quality components used in all KITs
Coverage of classic and new high-tech solutions for the best system coverage

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$35.99

High-precision and High-quality components used in all KITs
Coverage of classic and new high-tech solutions for the best system coverage

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$24.29

High-precision and High-quality components used in all KITs
Coverage of classic and new high-tech solutions for the best system coverage

from

$16.49

High-precision and High-quality components used in all KITs
Coverage of classic and new high-tech solutions for the best system coverage

Top Picks for 1978 GMC K25 Transmission Mounts

Upgrade GMC K25s with top-quality Transmission Mounts parts, including 9 OEM and aftermarket selections for your 1978 model.

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from

$6.99

Anchor 2108 This mount supports the transmission and dampens vibration. Each mount is specifically engineered and designed to OE standards. Natural and SBR rubber provide maximum life and performance. Steel fasteners are heat treated grade 5 bolts. A special bonding agent is used to ensure a rubber to metal bond. Rubber material is mixed to specific Durometer, hardness.

Product Features:

MAXIMUM LIFE & PERFORMANCE: Both natural and SBR (Styrene Butadiene) rubber provide good abrasion resistance and aging stability to ensure maximum life and performance.
MEETS OR EXCEEDS DUROMETER MEASUREMENTS: All rubber material is manufactured to specific Durometer (hardness) measurements based on the vehicle’s application requirements.
HARDENED STEEL FASTENERS: All fasteners are made of hardened steel with heat treated Grade #5 bolts.
SUPERIOR BOND: A special Chemlok bonding agent is used to ensure a superior rubber-to-metal bond.
HYDRAULIC MOUNT DESIGN: Hydraulic Mounts (applicable where OE) are designed for most front wheel drive vehicles because transverse drive train mounting.
For Years: 1955-1991
Weight approx: 1 Lbs
Reuse Bracket

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$10.49

Anchor 2107 This mount supports the transmission and dampens vibration. Each mount is specifically engineered and designed to OE standards. Natural and SBR rubber provide maximum life and performance. Steel fasteners are heat treated grade 5 bolts. A special bonding agent is used to ensure a rubber to metal bond. Rubber material is mixed to specific Durometer, hardness.

Product Features:

MAXIMUM LIFE & PERFORMANCE: Both natural and SBR (Styrene Butadiene) rubber provide good abrasion resistance and aging stability to ensure maximum life and performance.
MEETS OR EXCEEDS DUROMETER MEASUREMENTS: All rubber material is manufactured to specific Durometer (hardness) measurements based on the vehicle’s application requirements.
HARDENED STEEL FASTENERS: All fasteners are made of hardened steel with heat treated Grade #5 bolts.
SUPERIOR BOND: A special Chemlok bonding agent is used to ensure a superior rubber-to-metal bond.
HYDRAULIC MOUNT DESIGN: Hydraulic Mounts (applicable where OE) are designed for most front wheel drive vehicles because transverse drive train mounting.
For Years: 1955-1989
Weight approx: 2 Lbs
Reuse Bracket

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$46.49

A true performance application component for cars, trucks, hot rods, racing/competition, yet popularly used for street vehicles when more horsepower is added. Soft running enough to absorb vibrations for street use yet rugged for racing use. Helps control torque on high performance vehicles. Maintains proper drive shaft angle to help prevent early wear and unexpected power train damage. Replaces the original, short lived and typically too-soft rubber mounts and outdates those hard-running metal transmission mounts. Resistant to under vehicle fluid oils, coolants and road contaminants. Made of Energy’s Hyper-Flex performance polyurethane and heavy duty hardware – for added durability.

Product Features:

Unique Safety Interlock Design
Impervious to Vehicle Oils and Chemicals
Strong Enough Too Handle High Performance

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$90.99

Unique Safety Interlock Design
Impervious to Vehicle Oils and Chemicals
Strong Enough Too Handle High Performance

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$99.99

Constructed of durable polyurethane to handle the stress oh high horsepower. Absorbs vibration and lasts longer than rubber Features unique built-in safety lock to keep from separating under high torque loads. Ideal for use on street or strip applications. Complete with grade-8 mounting hardware.

Product Features:

Durable Polyurethane
Absorbs Vibration
Last Longer Than Rubber
Built-In Safety Lock

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$105.99

Unique Safety Interlock Design
Impervious to Vehicle Oils and Chemicals
Strong Enough Too Handle High Performance

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$71.99

With over 40 years of history, Nolathane remains the number 1 replacement and enhancement bushing and chassis component brand throughout Australia & New Zealand and now boasts a warehouse in California & catalog to suit the North American market.

Product Features:

Kit Contains: 4 bushings, 2 Tubes, 2 Plates, Install Guide

from

$53.99

Product Features:

Durable polyurethane to handle the stress of high horsepower
Same durometer as other BlackHeart and Hooker poly mounts
Can be used in place of 1-bolt or 2-bolt mount
Absorbs vibration and last longer than rubber
Ideal for use on street or strip applications
Molded indentions for socket clearance to ease installation
Complete with Grade 8 mounting hardware
Bolt Spacing on the Wider Side: 4-inch
Bolt Spacing on the Narrow Side: 1.5-inch

from

$48.99

Product Features:

Durable polyurethane to handle the stress of high horsepower
Same durometer as other BlackHeart and Hooker poly mounts
Can be used in place of 1-bolt or 2-bolt mount
Absorbs vibration and last longer than rubber
Ideal for use on street or strip applications
Molded indentions for socket clearance to ease installation
Complete with Grade 8 mounting hardware
Bolt Spacing on the Wider Side: 4-inch
Bolt Spacing on the Narrow Side: 1.5-inch

In-Demand Transmission Seals for 1978 GMC K25s

Select from 29 premium Transmission Seals parts for your 1978 GMC K25, with prices ranging from $3.19 to $123.99.

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from

$10.99

Design type: spring loaded; single-lip
Temperature range: -20 Deg. F to 300 Deg. F / -29 Deg. C to 49 Deg. C
Resistance to EP lubricants
Low swell in hydrocarbon fluids
Delivers quality and reliable performance for every type of repair

from

$4.99

Value-priced seal meets all cataloged application requirements.

Product Features:

Brand may vary by location

from

$9.59

AT SEL SHAFT SEAL

from

$24.49

Product Features:

Design type: spring loaded; multi-lip
Temperature range: -40 Deg F to 225 Deg F / -40 Deg C to 107 Deg C
Good low temperature capability
Low swell in hydrocarbon fluids
Delivers quality and reliable performance for every type of repair

from

$6.39

AT DPSTK TUBE SEAL

from

$6.99

Product Features:

Design type: springless; single-lip
Temperature range: -40 Deg. F to 225 Deg. F / -40 Deg. C to 107 Deg. C
Good low temperature capability
Low swell in hydrocarbon fluids
Delivers quality and reliable performance for every type of repair

from

$13.99

Value-priced seal meets all cataloged application requirements.

Product Features:

Brand may vary by location

from

$7.79

Value-priced seal meets all cataloged application requirements.

Product Features:

Brand may vary by location

from

$12.99

AT EXT HOUSING SEAL

from

$9.99

Motive Gear offers some of the toughest drive train components on the market today. If you are looking for the largest line of performance ring and pinion gear options available with gear sets in a wide range of ratios for nearly every application, both on and off-road, check out Motive Gear. Motive Gear products can be found in the winner’s circle at racing events worldwide. The superior quality of Motive Gear components is the result of years of racing development, outstanding design and state-of-the-art manufacturing methods. Extensive testing is performed on all products by our in-house engineers.

from

$9.59

AT EXT HOUSING SEAL

from

$3.19

Product Features:

ATP Transmission Seals And Gaskets are exact fit, no compromise replacement parts

from

$4.19

AT DETENT CABLE SEAL

from

$5.99

Design type: springless; single-lip
Temperature range: -40 Deg. F to 225 Deg. F / -40 Deg. C to 107 Deg. C
Good low temperature capability
Low swell in hydrocarbon fluids
Delivers quality and reliable performance for every type of repair

from

$12.99

Design type: spring loaded; multi-lip
Temperature range: -40 Deg. F to 225 Deg. F / -40 Deg. C to 107 Deg. C
Good low temperature capability
Low swell in hydrocarbon fluids
Delivers quality and reliable performance for every type of repair

from

$8.99

Design type: springless; multi-lip
Temperature range: -40 Deg. F to 225 Deg. F / -40 Deg. C to 107 Deg. C
Good low temperature capability
Low swell in hydrocarbon fluids
Delivers quality and reliable performance for every type of repair

from

$10.79

AT SPEED PINION SEAL

from

$22.29

from

$123.99

ManTransBrg-SealKit

from

$14.49

Value-priced seal meets all cataloged application requirements.

Product Features:

Brand may vary by location

from

$9.59

AT EXT HOUSING SEAL

from

$5.99

AT SEAL

from

$92.99

ManTransBrg-SealKit

from

$18.49

All Motive Gear products are engineered for their specific application and manufactured in state of the art facilities. All of our products undergo rigid quality control processes to insure proper fit, performance and longevity. Motive Gear products can be found in the winners circle at NHRA, IHRA, NMRA, NMCA, SODA, SCORE, BITD, Ultra-4 and NASCAR events because we offer unmatched selection and quality demanded by racers and their crew chiefs – the same quality and selection demanded by DIY customers and top mechanics. With four warehouses strategically located across North America, most Motive Gear orders arrive within 2-4 days. Win with Motive Gear!

Most Sold 1978 GMC K25 Automatic Transmission Parts

Explore our best-selling GMC parts for the 1978 K25 among 20 OEM and aftermarket options starting from $4.29.

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from

$4.29

AT SOLENOID SEAL

from

$21.99

Fully adjustable vacuum modulator to maintain accurate shift points.

Product Features:

Meets or exceeds OE fit, form and function

from

$33.99

Fully adjustable vacuum modulator to maintain accurate shift points.

Product Features:

Meets or exceeds OE specifications

from

$11.99

This clutch pilot bushing is designed to match the fit and function of the original part on specified vehicles. Made of quality materials, it is engineered for reliable performance.

Product Features:

Direct replacement – this clutch pilot bushing matches the fit and function of the factory part on specified years, makes and models
Ideal solution – this bushing is a reliable replacement for an original part that has failed due to fatigue
Durable construction – this part is made from quality materials to ensure reliable performance and long service life
Trustworthy quality – backed by team of product experts in the United States and more than a century of automotive experience

from

$34.49

Includes dipstick with chromed steel handle and chromed steel dipstick tube with mounting tab. 27 inch long.

Product Features:

Fits GM Th350 – Chevy Specific. Modify For Others
27 In Length
Chrome Plated Steel

from

$49.99

B&M’s vacuum modulator is fully adjustable, this allows you to tailor your shift points to within a range of 2-4 mph. Comes preadjusted for normal shift points. For TH350 and TH400.

Product Features:

Fully Adjustable
Allows You To Tailor Shift Points
Comes Supplied Pre-Adjusted

from

$23.99

Includes brackets, grommets, etc to match original
Helps transmission determine ideal downshift
Improves vehicle performance

from

$9.59

AT OIL PUMP ORING

from

$51.99

AT MODULATOR VALVE

from

$49.99

ATP Universal Fit Detent Cables are designed to cover many applications and are no compromise replacement parts

Product Features:

Includes brackets, grommets, etc to match original
Fits many GM transmissions
Adjustable

from

$21.99

AT MODULATOR VALVE

from

$11.79

AT FRT PUMP BUSHING

from

$48.99

Application matched component ensures the transmission gear position system can be returned to like new condition.
Product constructed to meet all design and operating characteristics as intended by the vehicle manufacturer.
This part will look and function just like the original unit being replaced.

from

$95.99

Billet aluminum handle with flexible braded steel tube mounts to the firewall. 29-3/4 inch long.

Product Features:

Braided Stainless Steel
Firewall Mounting
Includes Oil Fill Tube

from

$118.99

AT CONTR SOLENOID

from

$99.99

When swapping the TH400 transmission into any vehicle, this kit makes installation of the transmission’s kickdown feature a snap. This switch mounts to either a TH700R4, TH200, TH200-R4 or TH350 throttle cable bracket.

Product Features:

Allows High Speed Cruise
Cruise In Overdrive
Prevents Part Throttle Kickdown
Quick Installation

from

$33.99

Cable Bracket, GM (Bandit style shifters only) APPLICATION: For TH-400, 350, 250, 200, 700R4, 200-4R with 80797, 80798 or 81050 shifter.

Product Features:

Shifter Service Parts
Steel
Natural Finish
Sold individually
Replacement for Bandit shifters

from

$29.99

AUTO TRANS BAND

from

$13.79

AT CLUTCH PLATE

from

$9.59

AT CLUTCH PLATE

Top-Rated Transmission Parts Brands For Your 1978 GMC K25

Shop for the best-rated brands offering Transmission Parts and other products for your 1978 GMC K25s. Below you’ll find some of our best rated Transmission Parts from National, B & M, and Imperial, and more. Transmission Parts from these brands that fit a 1978 K25 start at just $8.99 and are rated as high as 4.3 stars. OEM and aftermarket Transmission Parts don’t get more top quality, durable, and affordable than from the brands below.

Popular National 1978 GMC K25 Transmission Parts

When it comes to maintaining or upgrading your 1978 GMC K25, using quality Transmission Parts is essential to ensure durability and a perfect fit. National ticks all of those boxes. We offer a wide selection of National Transmission Parts, specifically designed for the 1978 GMC K25. With over 3 National brand Transmission Parts in stock, you’re sure to find what you need. The prices for these top-notch parts start as low as $8.99, with an average price of just $14.82. Plus, with over 9 customer reviews and an average rating of 4.3 stars, you can trust that our National Transmission Parts will get the job done right. Choose Advance Auto Parts for reliability, quality, and expert-approved parts that keep your vehicle running strong.

from $8.99

(4)

Bearing Race

“Goes with M88010 bearing cup. Application was the pinion bearing race for a Ford 9 Inch on a 1957 Ford F-100.”

from $24.49

(1)

Multi Purpose Seal

“Fits right the first time… No more leaks…”

from $10.99

(4)

Multi-Purpose Seal

“it worked”

Popular B & M 1978 GMC K25 Transmission Parts

B & M auto parts is one of the highest quality Transmission Part brands in the market. Any 1978 GMC K25 owner should feel confident when installing genuine B & M parts in their vehicle. To ensure the best fit and performance for your 1978 K25, Advance Auto Parts carries a full inventory of 3 B & M Transmission Parts. Plus you will be keeping your GMC in peak condition while saving money because prices on these B & M Transmission Parts range from $33.99 to $382.99, plus, with more than 3 customer reviews and an impressive 4.1 stars average rating, you can be confident the Fram Transmission Parts below will deliver on both quality and value.

from $48.49

(1)

Shifter Accessories, Bracket and Lever Kit Fits TH400/TH350/TH250/200-4R/700R4

“Cable not perfectly straight. It is hard to believe as long as B&M and th400s have been around, that they do not line up better”

from $382.99

(1)

Tork Master 2400

“The B&M 2400 stall converter was a great choice for my application. It works well on the street and track, increased performance by leaps and bounds. ”

from $33.99

(1)

Cable Bracket

“Use it for a 700R4 swap, need to use B & M cable to fit”

FAQs for 1978 GMC K25 Transmission Parts

Which Transmission Parts are best-sellers for 1978 GMC K25s?

Out of 155 Transmission Parts that fit 1978 GMC K25s, the following parts are the top sellers:

Mounting Kit System (6014844) – $11.99
Multi-Purpose Bearing (3275876) – $35.99
Econo-Kool Transmission Oil Cooler (6014720) – $40.99

What’s the price range for 1978 GMC K25 Transmission Parts?

Transmission Part prices for the 1978 GMC K25 start at $3.19 and go up to $1,349.99 for the most premium parts.

What’s the average price of a Transmission Part for a 1978 GMC K25?

The average price for Transmission Parts for the 1978 GMC K25 is $148.54. Keep in mind the variety of part types within our Transmission Part category so you are likely to find a wide range of prices across a variety of parts and components.

Does Advance Auto Parts sell Transmission Parts for other GMC K25 model years?

Yes, we currently carry Transmission Parts for 2 model years of GMC K25s between 1975 and 1977. Transmission Parts are bought most frequently for the following model years: 1977, 1976, and 1975.

What are the cheapest Transmission Parts for my 1978 GMC K25?

The cheapest 1978 GMC K25 Transmission Parts we carry in stock are:

Automatic Transmission Speedometer Pinion Seal (11236107) – $3.19
Shift Shaft O-Ring (12009712) – $3.99
AT DETENT CABLE SEAL (10861007) – $4.19
AT SOLENOID SEAL (11239035) – $4.29
Oil Seal (5440610) – $4.99

What are the top-rated Transmission Parts that fit the 1978 GMC K25?

Out of 1,826 reviews by customers, our 1978 GMC K25 Transmission Parts have an average customer rating of . These are some of the highest-rated Transmission Part types for the 1978 GMC K25 and their top-rated products:

Automatic Transmission Differential
- Multi-Purpose Bearing (3275876) – $35.99

What types of Transmission Parts do you sell for my 1978 GMC K25?

As of 3/1/26, these are some of the most in-demand types of Transmission Parts for a 1978 GMC K25:

Can I get help with 1978 GMC K25 Transmission Part orders?

Contact our customer support team, by chat or phone, through the help desk page, where you can find instant answers about GMC Transmission Parts and more.

What is your return policy for GMC K25 Transmission Parts?

Advance Auto Parts keeps returns simple. For new GMC K25 Transmission Parts and accessories, your online orders can be returned, in their original condition, within 45 days. For requirements, see the returns page.

1978 GMC K25 Transmission Parts

ATP – AT OIL PUMP ORING (Part No.SO-21)

ATP – AT CONTR SOLENOID (Part No.SE-1)

B & M – Transmission Cast Deep Pan, Brushed Finish – TH400 (Part No.20280)

B & M – Cable Bracket (Part No.30499)

Imperial – Transmission Oil Cooler Reinstallation Kit (Part No.248002)

B & M – Chrome Deep Transmission Pan For TH 350 Transmission (Part No.30289)

ATP – AT EXT HOUSING SEAL (Part No.HO-8)

ATP – ATP Automatic Transmission Detent Cable (Part No.Y-100)

Schaeffler – Shaft Seal (Part No.SS2569)

ATP – AUTO TRANS BAND (Part No.JX-58)

ATP – AT CLUTCH PLATE (Part No.JC-50)

National – Multi Purpose Seal (Part No.8792S)

ARP Auto Racing – For Use With 90 Degree V6 Chevy/ 305, 502 V8 With 1 Piece Rear Seal (Part No.200-2906)

National – Multi-Purpose Bearing (Part No.A-35)

ATP – AT MSTR REP KIT PLUS (Part No.JMS-9)

National – Multi-Purpose Seal (Part No.2287)

Imperial – Mounting Kit System (Part No.226201)

National – Multi-Purpose Seal (Part No.6712NA)

Imperial – Transmission Line Fitting Kit (Part No.240390)

ATP – AT SOLENOID SEAL (Part No.JO-15)

B & M – Kickdown Cable For TH-350 Transmission (Part No.30287)

Schaeffler – Cone (Part No.KM86649)

Imperial – High Performance Transmission Oil Cooler (Part No.240512)

Mr. Gasket – Automatic Transmission Oil Pan Gasket (Part No.8690)

Carquest Premium – Automatic Transmission Modulator Valve (Part No.VMC1023)

Pro-King – Automatic Transmission Vacuum Modulator (Part No.MD-28)

Hays – Converter: Th350 28-3200 Stall (Part No.97-1B28Q)

B & M – Torque Converter, Nitrous Holeshot 2400 (Part No.20480)

Imperial – High Performance Transmission Oil Cooler (Part No.240516)

Imperial – Maxi-Kool XL Transmission Oil Cooler (Part No.243007)

Imperial – Mounting Kit System (Part No.226201)

Imperial – Econo-Kool Transmission Oil Cooler (Part No.242010)

Imperial – Econo-Kool Transmission Oil Cooler (Part No.242009)

Imperial – Maxi-Kool XL Transmission Oil Cooler (Part No.243012)

Imperial – Econo-Kool Transmission Oil Cooler (Part No.241018)

Imperial – Plate and Fin Style Transmission Cooler, Heavy Duty, 3/4" x 9-1/2" x 11" (Part No.243008)

Imperial – Econo-Kool Transmission Oil Cooler (Part No.242012)

Imperial – High Performance Transmission Oil Cooler (Part No.240514)

Imperial – Transmission Oil Cooler Reinstallation Kit (Part No.248002)

Imperial – High Performance Transmission Oil Cooler (Part No.240512)

Imperial – Econo-Kool Transmission Oil Cooler (Part No.242016)

Imperial – Transmission Oil Cooler (Part No.241015)

National – Bearing Race (Part No.M88010)

Driveworks – Wheel Bearing: Direct Fit, 1 Piece (Part No.S-5707)

National – Tapered Roller Bearing Cone (Part No.LM501349)

Driveworks – Taper Bearing Cone (Part No.S-M-88048)

National – Tapered Roller Bearing Cone (Part No.25590)

Driveworks – Taper Bearing Cup (Part No.S-LM-501314)

National – Bearing Race (Part No.2720)

Schaeffler – Bearing – CRB (Cylindrical Roller Bearing) (Part No.FC67147)

Schaeffler – Tapered Roller Bearing (Part No.KT63)

Schaeffler – Cone (Part No.KM86649)

Schaeffler – Cup (Part No.M802011)

Anchor – Transmission Mount: Left, Right, 1 Piece (Part No.2108)

Anchor – Transmission Mount: Left, Right, 1 Piece (Part No.2107)

Energy Suspension – Transmission Mount (Part No.3.1108R)

Energy Suspension – High-Performance Transmission Mount for Increased Durability (Part No.3.1106G)

Lakewood – Trans Mount: Urethane-Chevy (Part No.24350)

Energy Suspension – Transmission Mount (Part No.3.1132G)

Nolathane – Transmission Mount Bushing (Part No.REV208.0022)

Hooker BlackHeart – Hooker BlackHeart Polyurethane Transmission Mount – Red (Part No.71223030HKR)

Hooker BlackHeart – Hooker BlackHeart Polyurethane Transmission Mount – Black (Part No.71223029HKR)

National – Multi-Purpose Seal (Part No.6712NA)

Driveworks – Oil Seal (Part No.S-9613S)

ATP – AT SEL SHAFT SEAL (Part No.SO-19)

National – Multi Purpose Seal (Part No.2286)

ATP – AT DPSTK TUBE SEAL (Part No.SO-35)

National – Multi Purpose Seal (Part No.8792S)

Driveworks – Oil Seal (Part No.S-5778)

Driveworks – Oil Seal (Part No.S-9449)

ATP – AT EXT HOUSING SEAL (Part No.HO-9)

Motive Gear – Differential Pinion Seal (Part No.5778)

ATP – AT EXT HOUSING SEAL (Part No.SO-22)

ATP – Automatic Transmission Speedometer Pinion Seal (Part No.SO-13)

ATP – AT DETENT CABLE SEAL (Part No.SO-36)

National – Multi-Purpose Seal (Part No.240735)

National – Multi-Purpose Seal (Part No.410085)

National – Multi-Purpose Seal (Part No.2287)

ATP – AT SPEED PINION SEAL (Part No.SO-34)