Locks Flywheel in Place When Removing Harmonic Balancer on 6.6L Duramax Engines with Allison Automatic Transmissions. Saves time by locking the flywheel at the transmission instead of having to remove the starter for water pump replacement. On 2500 and 3500 pickups, remove metal spring-loaded inspection plate on the bottom of the transmission. Tool should slide into opening toward engine with the top of the tool engaging the teeth of the flywheel. On 4500 and 5500 trucks, remove the rubber inspection cap on the bottom of the transmission. Insert the tool at the front of the opening to engage the flywheel and hand tighten bolt to hold tool in place. Use 36mm 12 point socket with 3/4" square drive to remove harmonic balancer bolt and retorque on installation. 36mm 12 point socket can also be used on axle nuts.