Lisle 22100 Flywheel Locking Tool for 6.6L Duramax - Fast Harmonic

In this review the Lisle 22100 proves to be a straightforward, purpose-built tool for technicians and DIYers who work on 6.6L Duramax engines with Allison automatic transmissions. The bottom line: it locks the flywheel at the transmission so removing and reinstalling the harmonic balancer becomes faster and less fussy than pulling the starter. For anyone changing water pumps or crank pulleys on 2500/3500 and 4500/5500 trucks, this tool saves time and removes a common source of frustration.

Key Features

• Transmission-side flywheel lock: Locks the flywheel in place at the transmission opening so the harmonic balancer bolt can be removed without another person holding the crank.
• Fits Allison transmissions on 6.6L Duramax: Designed specifically to slide into the inspection opening and engage the flywheel teeth on applicable 6.6L diesel pickups and medium duty trucks.
• Use with common sockets: Accepts a 36mm 12-point socket and 3/4in square drive for removal and re-torque of the harmonic balancer bolt.
• Simple install: Slides into the transmission inspection hole after removing the metal plate or rubber cap and hand tightens a bolt to hold the tool engaged.
• Compact package: Small footprint and light weight make it easy to store in a toolbox or include with a water pump or pulley service kit.

Who It's For

The Lisle 22100 is aimed at mechanics, fleet technicians, and experienced DIY owners who frequently service 6.6L Duramax-powered 2500/3500 pickups and 4500/5500 trucks with Allison automatics. It is especially useful when a water pump or crank pulley replacement would otherwise require starter removal or awkward holding methods.

Those who should look elsewhere are owners of vehicles without the specified transmission opening or non-6.6L engines; this is not a universal flywheel tool and only applies where the transmission inspection port and flywheel tooth engagement are accessible.

Pros & Cons

Pros

• Locks the flywheel reliably at the transmission for single-person harmonic balancer removal.
• Compatible with a 36mm 12-point socket and 3/4in drive for torque work without extra adapters.
• Saves time by avoiding starter removal during water pump jobs on compatible trucks.

Cons

• Only fits 6.6L Duramax engines with Allison automatic transmissions and requires the inspection plate or cap to be removed first.

Specifications

Product	Flywheel locking tool
Model	22100
Fits engines	6.6L Duramax with Allison automatic transmissions
Socket required	36mm 12-point with 3/4in square drive
Recommended use	Remove and re-torque harmonic balancer bolt; water pump and crank pulley service
Package dimensions	4.5 in width x 5 in height x 2 in depth

Our Verdict

The Lisle 22100 is a focused, cost-effective tool for anyone who services 6.6L Duramax engines with Allison transmissions. It removes a common service bottleneck by holding the flywheel at the transmission opening, saving time and avoiding starter removal. For compatible trucks it is good value, durable in use, and makes harmonic balancer and water pump jobs noticeably easier.

Frequently Asked Questions

Will this tool work on my Duramax?
If your truck has a 6.6L Duramax with an Allison automatic transmission and an accessible transmission inspection opening, this tool is made to engage the flywheel teeth and will work.

Do I need special sockets or drives?
You will need a 36mm 12-point socket and a 3/4in square drive to remove and re-torque the harmonic balancer bolt as recommended.

Does it require removing the starter?
No; the tool is intended to lock the flywheel at the transmission so starter removal is not necessary for most water pump and crank pulley jobs.