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Jeep Cherokee - Push-Button Differential Lockup

Posted in Vehicle Reviews on November 15, 2004 Comment (0)
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Jeep Cherokee - Push-Button Differential Lockup
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Remember hearing about that bitchin' new selectable electric locker made by Eaton? It came out around the same time as the Hummer H2, and was offered as an option in the Hummer's build sheet. But whom do you know who has had one and gotten experience with it (besides your buddy with his bling H2, who probably never engaged it anyway)?

This is the Eaton E-Locker. It's been out for a while, but for--what?--like, two applications? Once it had created applications for GM axles and the Ford 8.8, Eaton chose to concentrate on other ventures within the company, and further applications of the E-Locker were shunned until a later date. But after much coaxing from the inside by aftermarket business and marketing manager Jeff Phillips, Eaton is finally releasing the E-Locker for Dana applications. The Dana 44 and Dana 60 applications will be out by the time you read this, and an AMC 20 application will be out by year's end.

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The Technical
The Eaton E-Locker is an electric-locking selectable differential. It instantaneously goes from a fully open mode to a full-spool mode with the push of a dash-mounted engagement button. The E-Locker features a rebuildable design, though with precision forged gears and a lack of any external module, air compressor, or air lines, the reliability is almost unquestionable.

When activated, an electromagnet engages a ball ramp, forcing three ball bearings out of a pocket, which in turn pushes six locking pins into corresponding slots. This causes the side gears to lock to the case and prevents the spider and side gears from turning. Consequently, this locks the axleshafts to the carrier, turning a fully open differential into a full spool.

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At Drivetrain Direct, Martin and Miguel Barraza (the notorious Barraza Brothers) started the installation by getting all the parts we needed together. We were also changing the gear ratio and putting axleshafts into the bare rear 44 housing we scored off a friend. We used Superior axleshafts, 4.56 gears from Drivetrain Direct, Superior gear oil, and overhaul kits with Timkin bearings.

Unlike a standard diff install, we needed to mark off and drill a 1/2-inch hole on the right side of the housing in front of the lip for the two-wire connection of the E-Locker. Miguel Barraza made sure to clean the entire inside of the housing very well, so as not to leave trace contaminants of previous parts or of the hole he just drilled. Once it was clean, he pressed a new bearing onto the pinion gear and installed it in the pumpkin.

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With the pinion in, Martin Barraza bolted the ring gear onto the E-Locker and installed the bearing, and gingerly massaged the diff in using a deadblow hammer, as the fitment is very tight. Once the locker was in the housing and the gear teeth were correctly meshed together using the correct amount of shims, Martin Barraza routed the two-wire connection through the previously drilled hole on the top of the housing. He used a small amount of silicone to ensure that gear oil would not leak out of the hole. With the locker installed and the wires routed, Martin Barraza installed the Superior axleshafts and brakes, replaced the diff cover, and filled the pumpkin with 90-weight gear oil.

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The wiring of the Eaton E-Locker is fairly simple, with two wires coming out of the differential and going to a relay. One wire is negative, one wire is positive. It doesn't matter which is which as long as you have one of each. The relay is a heavy-duty unit very similar to an auxiliary-light relay and is activated by the flip of a switch. The E-Locker's interior pushbutton acts as a "remote on" positive signal that triggers the relay to send energy to the locker's electromagnet, engaging the locker. Eaton includes all the necessary wiring, connectors, relay, and switch, so you will need nothing but wire cutters and some crimpers to wire your E-Locker up.

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How'd It Work Off-Road?
We finished the locker installations, scrambled to get a new door on our rig (don't ask), and hauled ass to Moab before even trying to engage the lockers. Yeah, we were asking for trouble, but we had faith and no time, so it was this way or no way.

We got out to Moab, wired up the relays and switches in the hotel parking lot at about 6 a.m., and were already stuck on Moab Rim Trail by 7:30 a.m. It was time to try the lockers. At the push of a button, we heard...nothing. Not a sound. Thinking that there must be some sort of sound during actuation, we retraced all wiring connections to make sure that the lockers were getting juice. After finding nothing wrong, we actually tried to move the vehicle, and to our embarrassment found that the lockers had been engaged the entire time while we held up the trail. Very impressive, not one clunk or thud during engagement. The only indication of the locker being engaged (besides the enhanced traction) is the lit-up switch.

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Around Moab for a week and then in San Luis Obispo, California, we slammed on 'em hard using 35-inch Krawlers, probably one of the heaviest tires on the market, and probably close to or past the capacity of a 30-spline axle. Never once did the lockers temporarily disengage or allow minor slippage like an automatic locker would. They stayed locked in full-spool configuration until a silent disengagement of the differential with another push of the button.

On the way back from Moab we started to hear a noise in the rear, but did not have time to do anything about it until after another wheeling trip. By that time, the sound had become so horrible that it resonated throughout the entire unibody. We finally went back to Drivetrain Direct to find out what we had done. Martin Barraza pulled the diff cover off to examine what the noise was. It was pretty obvious, and some simple deduction led us to the original source of the problem. Apparently the rear axle had wrapped enough to allow the existing diff skid to turn up and smash into the driveshaft's slip yoke.

Amazingly, this did no damage to the driveshaft or U-joint, but it completely wasted the pinion bearing, allowing the pinion to move back and forth and eat into the middle of the carrier as shown in this picture. Oh crap, had we just destroyed one of five Dana 44 E-Lockers in existence? But upon closer examination, we found it was only superficial scarring on the almost 1-inch-thick casing of the differential--nothing to even concern ourselves about. Barraza got the rearend back together and we were at it again the next weekend abusing the hell out of the lockers. To date, we haven't had a failure of the Eaton E-Locker, and we're really loving the simple pushbutton instantaneous actuation.

Sources

Drivetrain Direct
Corona, CA 92880
909-272-0158
www.drivetraindirect.com
Eaton Corp.
800-328-3850
www.eaton.com

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