An ARB diff lock for the FJ40

I waited 38 years to install an ARB differential locker in my FJ40.

Why so long, and what made me finally decide to do it? A number of reasons explain the delay. First is that the ARB diff lock did not exist until 1987—a pretty ironclad excuse for the first ten years I owned the vehicle. By the time I became aware of the product and its potential, in the early 1990s, I was using the Land Cruiser as a support vehicle for guiding sea kayak trips in Mexico. And sea kayak guides do not make enough to buy ARB lockers. Several years later I moved on to freelance writing—and freelance writers do not etc. etc.

By this time another factor was at work. Through much, much trial and error I had become intimately familiar with the vehicle and its capabilities on difficult trails, to the point that I could predict accurately when a wheel was going to lift, when a cross-axle obstacle would unload diagonal tires enough to steal traction, just how much momentum I needed to get through spots that would have been effortless with a locker. Thus I was beginning to enjoy successfully traversing trails in Arizona that were considered fairly advanced even with traction aids, and a sort of reverse snobbery seduced me. Of course there were plenty of challenges simply beyond the ability of an FJ40 with open diffs, a two-inch lift, and 31-inch-tall tires, but I was happy with the places I’d been.

 The fun part: drilling a hole in a perfectly good differential housing.

The fun part: drilling a hole in a perfectly good differential housing.

That attitude began to change when I had a Jeep Wrangler Rubicon Unlimited for a year as a long-term review vehicle for Overland Journal. The Rubicon, with its compliant all-coil suspension, driver-disconnectable front anti-roll bar—and selectable diff locks front and rear—could traverse terrain elegantly that the FJ40 traversed awkwardly. At the time I was stressing—and, a few years later, at the Overland Expo, teaching—environmentally conscientious driving, techniques far beyond the facile “Stay on the trail” message of Tread Lightly. One overriding goal of this is to avoid wheelspin if at all possible—an approach that is easier on the vehicle, the tires, and the trail. In the FJ40 some wheelspin was almost inevitable to get through sections that unloaded two tires, even with judicious left-foot braking, which can reduce but not eliminate it. In the Wrangler I could scan the terrain in front, predict which spots might unload the tires, and engage one or both lockers ahead of time, resulting in perfectly smooth progress. (This, by the way, is the salient advantage of driver-selectable lockers over ABS-based traction-control systems, even the best of which which must detect some wheelspin before they activate.)

Also contributing to my change of mind was the increasing capabilities of almost all current four-wheel-drive vehicles—some, such as that Wrangler and our Tacoma, equipped with factory locking diffs, many others with increasingly sophisticated traction control, even "lesser" models firmly in the cute ute category. Despite its relative primitiveness, I’ve kept the FJ40 competitive in some ways—on Old Man Emu suspension it rides better than our Tacoma did stock and has excellent compliance; it has a best-in-class Warn 8274 winch, good driving lights, a superb no-longer-made Stout Equipment rear bumper and tire/can carrier, a fridge, even a stainless-steel 14-gallon water tank. But newer vehicles were simply outclassing it in traction. 

Fast-forward to earlier this year, when I shipped the Land Cruiser to Bill’s Toy Shop in Farmington, New Mexico, for a complete engine and transmission/transfer case rebuild. As long as it was up there . . . 

I decided on a single rear locker. Why not another up front? Two reasons. First, this damn thing is now worth roughly ten times what I paid for it all those years ago, so I’m a bit more careful about where I take it. I think full traction on three corners is all I’ll need. Second, and probably more important, I still have the factory non-power steering, and a locking diff in front with manual steering would be, if not actually dangerous, stupendously difficult to control.

I took it for granted that with 320,000 miles on it, a fair amount of which was pulling trailers holding, at various points in history, a 21-foot sailboat; sea kayaks plus gear, food, and water for six clients; and cargo trailers ferrying Expo equipment, the diff would need a new ring and pinion gear, if not spider gears as well. Not so, said Bill—they were still in excellent condition. He replaced bearings and seals and called it good. An ARB High Output compressor in the engine compartment will double for tire inflation, saving precious cargo space I used to have to devote to a portable unit. I voted for installing the two switches in the dash, but Bill whined so piteously about sawing two rectangular holes in my unspoiled dash that I let him put them in the overhead shelf that houses the two-meter radio.

I’m now looking forward to quite a transformation in the faithful Forty, given fresh power, reworked transmission, and 50 percent more traction. It will be on its way back to Arizona in a few days.