Diff Locker Install

G80 Locker Repair

Heavy-duty Eaton Truetrac is a quick fix for failed GM G80 OEM lockers


By Tom Jackson

You push a truck hard enough – even a heavy duty model – and something’s going to give. When mechanic Dave Adair cracked the diff locker on his 2007 Chevy 2500 HD, he decided to step up to something beefier: an Eaton Truetrac.

Under some duress, the factory G80 limited slip, the gear that engages the limited slip, broke and would only engage in spots where there were still teeth on the gear.

Broken teeth from that gear accumulated on the magnetic differential drain plug.

Thanks to the design of the Chevy differential, the process was fairly straightforward. David, fellow mechanic Daniel Parker and drivetrain repair expert Jack Robertson removed the old locker and replaced it with the new in about four hours at Truck Supply and Outfitters in Tuscaloosa, Alabama.

The most challenging part of this rebuild is measuring the backlash on the ring gear. For this you need a machinist’s dial caliper.

Daniel borrowed his father-in-law’s setup, a Starrett model with a magnetic base and several adjustable arms which allowed him to position the business end precisely on a select tooth on the ring gear.

The backlash measurement is critical. If you get it too tight, the gear will not move. Too loose and the differential will whine and suffer excess wear. The ideal backlash will measure about .008 inches at three roughly equidistant spots on the gear.

You’ll need a helper to remove the ring gear and diff locker assembly and install the new, as the entire unit is very heavy.

This could be done on the ground with the truck up on jack stands, but like most well-equipped shops we had the convenience of putting the truck up on a lift. You will also need a bearing press.

The image gallery shows the step by step installation process.