How a Eaton G80 locker works

A GM C Sierra with an Eaton G80 locking differential traverses the ditch simulation. Click image to enlarge

With the locking axle, the vehicle was driven slowly on the roller and the wheel spun freely. By accelerating slightly so the spinning wheel is turning about 100 rpm or about 13 km/h, centrifugal weights in the differential latch to a locking mechanism that forces the differential gears to spread apart and engage clutches in the sides of the differential. Within one turn of the wheel, the clutches lock both sides together and the truck drives over the obstacle with ease. I have pulled out of icy parking spots with a GM vehicle equipped with an Eaton locking axle many times when I would have been stuck without one.

Another demonstration simulated driving the trucks over a ditch at an angle. When the truck was in the middle of the transition, one rear wheel and one front wheel had almost no load on them. With the four-wheel drive vehicles, both the one front and one rear wheel without load would spin and the truck would move no further. It was stuck. Even with four-wheel traction control, the vehicle remained stuck because the computer would reduce power at the same time it braked the spinning wheels. There still wasn’t enough torque transfer to the wheels with traction to get the truck moving.

As the two-wheel drive truck with the Eaton locking axle reached the transition, the unloaded rear wheel began to spin but within one turn of the spinning wheel the axle had locked and the truck drove through. It demonstrated that a locking axle in a two-wheel drive vehicle can perform better than four-wheel drive.





Eaton G80 locking differential. Click image to enlarge

Eaton’s locking differential is used for low speed traction. At speeds above about 30 km/h, a centrifugal weight disables the locking mechanism so that the wheels can turn independently. Unlike limited slip or Positrac differentials which have spring loaded clutches that are engaged at all speeds, the locking differential now allows one wheel to spin. This ensures vehicle stability if you encounter black ice on the highway. If both wheels were locked, they would both spin and the rear of the vehicle would have no stability. Without being locked, only one wheel spins and the other maintains some traction.

Traction at low speeds with the stability of an open differential at higher speeds: Eaton offers this for only about $300 as an option on GM trucks. It’s definitely worth the money.

Jim Kerr is a master automotive mechanic and teaches automotive technology. He has been writing automotive articles for fifteen years for newspapers and magazines in Canada and the United States, and is a member of the Automobile Journalists Association of Canada (AJAC).
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