Cherokee ARB Lockers and Gear change

How can my sleeper Cherokee with a baby 3.5" lift and tiny 31" tires keep up with the "real" Jeeps? My Secret Weapons are my two ARB differential lockers, front and rear. With two lockers, I go where everyone else goes. I'm dragging and scraping to be sure, but I get there!

Adding a differential locker is one of the more expensive--and one of the most potent--upgrades you can do. Wheeling with open differentials can make you a better driver, but there are some trails, obstacles actually, that just cannot be surmounted without a locker or two. And if you're part of a big group, you'll know who's got open diffs... the guy holding up the line!

Good Advice

I was fortunate to have good advice from knowledgeable friends when I decided to put a locker in the rear of my Cherokee. The advice was to pick a goal for your vehicle and move in that direction. In other words, don't spend money on a dead end. As I mentioned, I had decided to put one locker in the Cherokee. Suppose I did that. Later, liking the one locker so much, I decide to put another locker in the front. Done. Next I decide, because of my bigger tires, to change to lower gears. See? I've spent double or triple the money on parts and labor doing all these projects at different times. Thanks to my friends, I did all the inside-the-diffs work at the same time. Do your lockers, gears, bearings, oil seals, etc. all at the same time.

(That's not to say that I listened to my friends entirely, but you'll find out about that in the coming months. D'oh!)

Which Gears?

The gear ratio is just that... a ratio. A 4.10:1 (say "four ten to one") ratio means that the drive shaft will have to spin 4.1 times for the wheels to spin once. So lower (numerically larger) gears make the vehicle move more slowly. My Cherokee started with typically stock 28" tires and 3.55 gears. Moving to a 31" tires makes the popular 4.10 ratio a great choice. 4.10 gears and 31" tires will give me a combined ratio lower than stock with room to advance to 32" or even 33" tires without regearing. Without a diff gear reduction, the bigger tires would rob power from the Cherokee, not exactly a powerhouse to begin with.

Which Locker?

Debate between advocates of the venerable Detroit Locker and lovers of the selectable ARB air-powered locker is as hot as that between automatic and manual transmissions. Everybody's got an opinion! There are other fine solutions, but the Detroit and the ARB seem to have become the Hatfield and McCoy of lockers. Some say the Detroit has the edge on strength, but I hear stories of both types breaking. A failure in the air system will render the ARB useless, but its open, daily streetability is a powerful lure. The Detroit is locked when you need it to be locked, but can't be unlocked. That can make steering difficult (for a Detroit in the front) and daily driving clunky (for one in the rear). ARB in the front and Detroit in the rear? There truly is no right answer, and that's what makes this sport/hobby/obsession so fantastic! For me and my family the ARB's selectability was a siren-song... too tempting to refuse.

Installation

Like most people, I don't have the experience to install differential gears. I commissioned Brennan Hill of Hill 4 Wheel Drive in San Luis Obispo, CA to install the 4.10 gears from DriveTrain Direct and the ARB lockers.

While checking the backlash (is that the right word?) in the newly installed front gears, owner Brennan Hill was overheard saying, "It's perfect." That's one of the top ten phrases you want to hear your differential guy say. The next day, Brennan was checking the rear setup and said, "This is even better than the front!" Remembering back, I replied, "But you said the front was perfect." He quipped, "This is perfect plus two."

I didn't take a picture of Brennan until the job was finished. I grabbed two wrenches at random, gave them to him, and asked him to look busy. "OK," he said. "I'm tightening two fake bolts." I replied, "Now pretend you're not mad at me for taking your picture."

Installation of the ARB compressor

Before Hill did the hard work, I prepared for the ARB lockers by installing the ARB air compressor. Finding an installation location inside the engine compartment of a Cherokee isn't easy, even for something as small as the ARB compressor. I was not really choosing the "best" location... more like choosing the "least bad" spot. There seemed to be enough room above the brake equipment, so I fabricated some cheesy, but functional, brackets out of steel strap, relocated the hood release cable, and bolted on the compressor.

The wiring harness, supplied with the ARB compressor, makes the electrical portion of the installation easy. The only trick is finding a place in the firewall to route the wires to the inside of the cab. Somewhere near the hood release cable worked for me... in fact, I think I routed the wires through a hole I put into the cable's rubber grommet.

Installation of the ARB Activation Switches

Like in the engine compartment, there is little room inside the Cherokee. I needed a spot for three rather large ARB switches. An alternative could be to substitute smaller switches, but the ARB-supplied units are really nice, high quality ones... lighted and everything... so I fabricated a small switch panel. I'm not Mr. Fabricator, so you can do this, too. I found some aluminum (light, strong, cuts like butter) angle stock and did the work with simple tools. I used a hack saw, a file and a drill. My buddy Dan supplied the tap and die set that I used to supply the coolest feature of the assembly, the switch guard.

In the Field

We don't trailer, so drives of four, eight, or even 16+ hours to Moab are the rule, and the Cherokee sees about half-time duty getting me to work. That makes the open nature of the deactivated ARBs a blessing. The compressor comes in handy, too, for far more than just powering the lockers. At the end of the trail, we use it to air up the tires. Slowly, yes, but it gets the job done. Around town and at work, the compressor sees duty filling up clueless drivers with nearly flat tires. I love the look on their faces when I offer to fill up their tire on the spot.

How do the ARB lockers work? I already said that I call them my Secret Weapon, so that should tell you what I think of the ARBs. I get a lot of attitude from guys driving the classic style Jeeps and Toyotas and it gets old. They get that look like "Cherokee? Oh, brother, here comes a loser. Get out the winch cable." First of all (harkening back to the previously installed OME/TeraFlex suspension), I rarely need the lockers. The suspension is really flexy, and keeps the tires on the ground. But when I decide to hit one or both of the buttons, there's no stopping the Cherokee. We're currently running with 3.5" lift and, of course, the XJ has a large overhang in the rear. There's lots of crashing and banging, but we don't get stuck.

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