Lisle Flywheel Locking Tool for 6.6L Duramax Allison — Transmission‑Port Crank Lock, Fits 36mm/3/4" Drive

If you maintain 6.6L Duramax V8 engines, the Lisle 22100 saves time and effort by locking the flywheel at the transmission opening instead of removing the starter or other components. Built specifically for GM 6.6L Duramax engines paired with Allison automatic transmissions, this tool lets you stabilize the crank for loosening and torquing the harmonic balancer bolt using a 36mm 12-point socket and 3/4" drive. The compact package fits neatly in a toolbox and is sized to engage the flywheel teeth through the transmission inspection port.

How does the Lisle 22100 lock the flywheel so I can remove the harmonic balancer?

The tool inserts into the transmission inspection opening and engages the flywheel teeth, holding the crank from turning while you apply torque to the harmonic balancer bolt. It relies on the transmission access point rather than removing the starter, simplifying access and reducing disassembly.

• Slide tool into transmission opening toward the engine to mesh with flywheel teeth.
• On 2500/3500 trucks remove metal spring-loaded inspection plate first.
• On 4500/5500 trucks remove the rubber inspection cap before inserting the tool.
• Hand-tighten the tool’s bolt to clamp it in place and prevent rotation.

What tools do I need with the Lisle 22100 for bolt removal and reinstallation?

Use a 36mm 12-point socket with a 3/4" square drive to remove and retorque the harmonic balancer bolt after the flywheel is locked. The same 36mm socket is commonly useful for other heavy-duty fasteners, like axle nuts.

• 36mm 12-point socket, 3/4" drive for harmonic balancer bolt removal and re-torque.
• Breaker bar or impact wrench (as appropriate) to provide required torque.
• Standard hand tools to remove inspection plate or rubber cap on the transmission.
• Torque wrench to confirm final bolt torque during reinstallation.

Which truck models and service tasks benefit most from this locking tool?

The Lisle 22100 is aimed at GM pickups and medium-duty trucks with the 6.6L Duramax paired to an Allison automatic. It especially helps jobs such as harmonic balancer removal, water pump replacement, or any service requiring the crank to remain stationary.

• 2500 and 3500 pickups: remove the metal spring-loaded transmission inspection plate.
• 4500 and 5500 trucks: remove the rubber inspection cap before insertion.
• Useful whenever crank locking is required without starter removal.
• Simplifies repeat maintenance by reducing disassembly time.

The Lisle 22100 ships in a compact package approximately 4.5" wide by 5" tall by 2" deep, making it easy to store in a service cart or toolbox. The tool’s engagement design targets flywheel teeth through common transmission access points for a solid hold while you torque or loosen major fasteners.

Who this tool is for: Professional mechanics, fleet technicians, and knowledgeable DIYers who work on GM 6.6L Duramax engines with Allison automatics and want a faster, less invasive way to hold the engine while removing or reinstalling the harmonic balancer. If you perform water pump jobs, harmonic balancer service, or frequent driveline maintenance on 2500–5500 series trucks, this tool reduces labor steps and protects surrounding components by avoiding unnecessary starter removal.