Features: 1. Benefits — Locks flywheel in place when removing harmonic balancer on 6.6L Duramax engines with Allison automatic transmissions. Saving time than removing the starter for water pump replacement. 2. Duramax 2500 / 3500 Pickups — Use toothed pieces only removes 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. 3. Duramax 4500 / 5500 Trucks — Use toothed pieces with screws 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. .