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1985 GMC Truck 4x4 - Eaton Electric Locker

Posted in Features on April 1, 2002
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Yep, it's here, it works, and it's truly revolutionary. The new fully selectable electrically activated ELocker from Eaton is a reality, and is available this fall to the aftermarket. You've heard rumors of electrically actuated lockers for some time now from various manufacturers, and the OE market such as Toyota and others have had them for awhile. In fact, the new H2 Hummer is factory equipped with the new ELocker, in a 14-bolt AAM axle from the factory.

What makes this unit so unique to our market is that it is the only locker that actuates with an electromagnetic ball-ramp locking mechanism that forces locking pins into one of the side gears, which is beautifully simple and durable. Other designs of electric lockers have solenoids or motors to actuate shift forks and collars, which could also be worked by a cable.

The ELocker has two simple wires that lead out of the housing, with no forks or collars to jam, break, or wear out. Air-actuated lockers, such as the ARB Air Locker, have pneumatic seals that can wear out or leak, and they also have the need for a compressed air supply and feed lines from the compressor to the ARB.

The ELocker installation is as easy as a standard diff, with virtually no modifications needed to the axlehousing or cover. With other air, cable, or electrically actuated lockers, either the cover needs to be replaced, or a hole has to be drilled into the axlehousing or cover for a bulkhead fitting. The factory H2 Hummer has a different bulkhead fitting designed into the housing as opposed to the aftermarket design, which of course is dependent on the different applications for the ELocker. The popular GM axle, such as the large and small 14-bolt, 12-bolt, and 10-bolt styles are the first to be released, with other popular axles such as Ford and the Dana 44 and 60 to follow.

We jumped at the chance to try out this revolutionary new design, and even visited the factory and proving grounds in Marshall, Michigan. Here, we actually took apart an ELocker, put it back together, installed it in an axle, and went out and thrashed the truck on a testdrive on the company grounds. Even though we didn't fiddle with the switch and harness install, which is very basic, the rest of the operation was so simple we knew we had to try one out ourselves.

We recently acquired an '85 GMC 31/44-ton 4x4 with the GM 911/42-inch 14-bolt rear axle, which is a perfect candidate for an ELocker. We're solid proponents of any style of locker over a limited slip, and since we'd be using this truck for towing and wheeling, we figured we'd torture the new Eaton unit for a while.

We trundled our beater truck down to Off Road Unlimited in Burbank, California, nd had no trouble convincing them to be the first shop to install an ELocker.

While we've only got a few thousand miles on this unit, it performs flawlessly in open or locked mode, and we'll keep you updated on how hard we hammer it and how it holds up. So far, this is one of the simplest and best selectable locking diffs made, and we can't wait to use them in our hard-core trail rigs.

How the ELocker WorksA standard or open differential is designed to allow the tires on an axle to rotate at different speeds around a turn, or differentiate the speed of the tires. By their very design it's evident that if one tire slips on a surface, the other tire receives no power. While this is fine for regular cars, severe-duty wheeling requires a locking differential at times, and an open one during regular use.

That is why a selectable locker has an advantage over spools or automatic lockers. In operation, the ELocker is normally a standard open diff, but when a dash-mounted switch actuates the unit, an electromagnet (A) mounted on the ring gear side of the differential is energized. The electromagnet causes the ball ramp mechanism (B) to engage. The ball ramp device is simple in concept and application. Three small ball bearings on a ramped surface are forced out of their pockets and up ramped grooves (C), which force the engaging mechanism in the diff. This mechanism consists of six pins (D), which slide into oval slots (E) on the backside of one axle gear, locking the gear to the case. This prevents the spider gears and other axle gear from rotating, locking the axleshafts to the carrier for a full locking differential. To unlock the ELocker, power is interrupted and the electromagnet force is released, and springs near the locking pins slide the engaging collar back into the open position as the balls move down into their pockets.

The ELocker works the same way in reverse, as the ramped grooves are on both sides of the pocket. This means the engaging mechanism could unlock if there is no tension on the spider gears when shifting from Drive to Reverse or back, but under trail conditions this seems unlikely. A slight bump or thud is all we notice when engaging, and that's a positive indication that the unit is working.


Off Road Unlimited
Eaton Corp.

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