Lisle Flywheel Locking Tool for GM 6.6L Duramax (Allison) — Model 22100, Heavy‑Duty Alignment for Harmonic Balancer

The Lisle 22100 is a purpose-built flywheel locking tool that secures the flywheel on 6.6L Duramax engines with Allison automatic transmissions so you can remove and reinstall the harmonic balancer safely and quickly.

This heavy-duty locking tool is engineered specifically for GM 6.6L Duramax diesel engines paired with Allison automatics. It holds the flywheel teeth in position at the transmission opening so you can apply torque to the harmonic balancer bolt without the engine turning. The design saves the extra step of starter removal on many chassis and speeds service tasks like water pump replacement or harmonic balancer removal and reinstallation.

How does this tool help when removing the harmonic balancer?

The Lisle 22100 engages the flywheel teeth at the transmission access point to prevent crank rotation while you loosen or tighten the harmonic balancer bolt. By stabilizing the crank at the transmission end, it eliminates the need to crank the engine or remove other components in many applications.

• Slides into the transmission inspection opening to engage flywheel teeth.
• Holds flywheel steady so a 36mm 12-point socket can remove the balancer bolt.
• Hand-tighten the tool bolt to lock position during service.

Where and how do you install the Lisle 22100 on different truck models?

Installation varies by chassis: on 2500/3500 pickups you remove the metal spring-loaded inspection plate; on 4500/5500 trucks you remove the rubber inspection cap at the bottom of the transmission. Insert the tool into the access opening toward the engine until the tool top engages the flywheel teeth, then secure it by hand as described in the service steps.

• 2500/3500: remove metal spring-loaded plate, insert tool toward engine.
• 4500/5500: remove rubber inspection cap, insert tool and hand-tighten.
• Always confirm tool tooth engagement visually before applying torque.

What additional socket and drive tools are required to use it effectively?

To remove and reinstall the harmonic balancer bolt you need a 36mm 12-point socket and a 3/4" square drive breaker or impact/wrench. The same 36mm 12-point socket is also compatible for axle nut removal on many Duramax applications, making it a useful multipurpose item in your toolbox.

• Use 36mm 12-point socket with 3/4" square drive for balancer bolt.
• Socket works for axle nuts as well, increasing utility.
• Recommended to have an appropriate torque wrench for re-torquing fasteners.

Who is this for? The Lisle 22100 is aimed at professional mechanics, fleet technicians, and DIY diesel owners who work on GM 6.6L Duramax engines with Allison automatics. If you perform harmonic balancer removal, water pump service, axle work, or other tasks that require locking the crank, this compact tool cuts service time and reduces disassembly steps. The package is compact (approximately 4.5" x 5" x 2") so it fits neatly into a shop drawer or mobile service kit.