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.

Airing down—and up—the pro way

One of the most frequent questions people ask me is, “What’s the the best thing I can do to improve my vehicle’s off-pavement performance?” Many of them seem distinctly disappointed when I answer, “Air down your tires.” I’m sure they’re hoping I’ll facilitate some expensive and impressive modification—diff locks, external-bypass shocks, three-piece titanium wheels, something that would justify putting a stylish brand sticker in a window. But the fact is that nothing is easier to do or more effective at providing several instant benefits than reducing your normal street tire pressures to suit the immediate conditions. I’ll repeat: Nothing.

First, lower pressure increases traction by increasing the contact area of the tire and allowing it to better deform around obstacles and grip them. Flotation in sand is enormously enhanced with the longer footprint provided by lower pressure (not so much greater width as many suppose).

But the advantages don’t end there. Lowering pressure alleviates stress on the vehicle by effectively reducing the spring rate—the tires flex enough to absorb impacts that would otherwise have to be dealt with by the springs and shocks. That translates to much greater comfort for the driver and passengers.

Finally, the above characteristics contribute to reduced impact on the trail. We saw first-hand evidence of this on a recent crossing of the Simpson Desert in Australia, via the Madigan Line—so-called after Dr. Cecil Madigan, who led the first scientific expedition across the area in 1939. The Madigan Line cuts directly across the huge field of parallel sand dunes that characterizes this part of the Simpson—1,130 sand dunes to be more or less precise. The dunes themselves are stabilized and well-vegetated, but the bare track still needs to ascend and descend each dune, and despite the very sparse traffic on this route the final approaches and crests are often cratered with “hoon holes,” where those who disdain airing down—or even engaging four wheel drive—have left huge divots from futilely spinning tires or frantic, lunging ascents.

Graham and I actually aired down our Land Cruisers prior to hitting the dunes, on the stretch leading to the old Andado Station, a fine track but well-known for its long stretches of corrugations (or washboard as we refer to them in the U.S.). I reduced our pressure from 40 psi, which we’d run on the paved Stuart Highway to Alice Springs, down to 32, and Graham did likewise (he’d found his tubed tires on split rims at a harsh 50 psi). It took much of the sting out of the sharp undulations and eliminated the skip-fishtailing that can occur with higher pressures. (An Australian writer described those corrugations as “brutal.” All I can say is he needs to see the corrugations on the seven-mile dirt track to our house in Arizona. Or those on the road from Namanga to Amboseli. But that’s another story.)

Once in the dunes, we further reduced pressure to around 22 psi. This is well above the 14 we might run in very soft sand, but it worked perfectly on the combination of flat, compacted inter-dune track and the chewed-up ascents and descents. We even summited the famous Big Red dune outside Birdsville with no drama.

Once past Birdsville, on the high-speed gravel Birdsville Developmental Road, we re-inflated—and that’s where the catch is for many people who grasp the concept of airing down, appreciate its advantages, but rarely if ever do it.

Why? Because a lot of those people carry a compressor that cost them as much as a couple of pizzas and is about as effective at actually adding air to a tire, despite the “150 PSI!” claims on the box. A single 45-minute session laboriously moving four tires from 25 psi to, say, 28, while their $29.95 compressor buzzes and vibrates in circles like an enraged chihuahua, and that’s it. The thing gets tossed in the bottom of the tools, to be used in the event of an actual flat, if at all. The same people likely used the point of their Swiss Army knife to depress the valve to deflate each tire, another laborious procedure. It’s little wonder they inflate the tires on their new truck to 40 psi and never budge from that.

We knew better. And we were, after all, in Australia, home of some of the best expedition equipment manufacturers on the planet. In Sydney we had picked up a pair of ARB E-Z deflators, and two ARB portable Twin compressor kits (CKMTP12). The single-cylinder ARB High Output compressor on our Tacoma has been working perfectly for several years operating a locker and inflating tires, so I was eager to compare the more powerful Twin in field use. 

Airing down takes less than a minute per tire with the E-Z deflator, which unscrews and captures the tire’s valve core, allowing a much greater volume of air to exit the valve stem, and gives you precise control with its sliding actuator. The only faster way I know to air down four tires is with a full set of the superb set-and-forget CB Developments Mil-Spec automatic deflators—but that full set will cost you $400, versus $40 for the ARB unit. An E-Z choice, if you will.

Regarding portable 12V compressors, as with so many other products it’s been my experience that you get what you pay for. The $30 units that plug into a cigarette lighter simply won’t cut it for field use. I know people who’ve been happy with the ubiquitous Masterflow MT50 and its variations, which are available for less than $100; these clip directly to the battery, meaning they can draw more amperage, but they are still achingly slow, and I can recall at least three failures related to me by users. Simply put, if you’re going to go the pro route for airing down (and repairing) tires, you need a pro-level compressor. You do not want to get caught after a section of soft sand with all your tires at 14 psi, no way to inflate them, and 30 miles of rocks ahead. (Especially when it's been six days since you've seen another human.)

Ignore the psi rating—virtually any pump will produce more than enough theoretical pressure. It’s the cfm (cubic feet per minute) rating and duty cycle you need to evaluate. The cfm is self-explanatory. Duty cycle refers to how long the unit can run before it needs to shut down and cool off. A 25-percent duty cycle means the pump can run for 15 minutes out of an hour. It’s easy to see the relationship: A high cfm rating means little if the duty cycle is poor, and a 100-percent duty cycle means little if the cfm rating is below standard. Furthermore, some compressors display an impressive cfm rating at zero psi, but will fall off significantly with higher pressures. Look for factory specs that list both. 

The Australian-built ARB Twin boasts a 100-percent duty cycle, produces 6.16 cfm at zero psi and an impressive 4.68 cfm at 29 psi. How does this relate to the real world? Back on the Birdsville Developmental Road to air up, I hooked up the Twin’s leads to our Land Cruiser’s battery, flipped the rocker switch, connected the chuck to the first tire (still at 22 psi), settled back on my heels to wait a couple minutes, and, er, what? The tire seemed to rise awfully quickly. I disconnected and checked the pressure: 42 psi. I was only aiming for 38 . . . 

I bled a bit out and moved to the other three tires. I didn’t set a watch to any of them, but it certainly took no more than a minute per tire to reinflate from 22 psi to 38. That rivals my benchmark for powerful compressors, the Extreme Outback ExtremeAir Magnum. And the ARB doesn't have a single "Extreme" in its name.

As a reliable and durable tool for remote use it would be hard to imagine a better configuration than the ARB Twin, given the extensive redundancy: Two all-ball-bearing motors, two cylinders, two inline fuses, and internal thermal protection for each motor. Twin air filters are washable sintered bronze, not paper. It’s highly moisture and dust resistant (the cooling fan is actually sealed to IP55 specs); the cylinder bores are hard anodized and the piston seals are Teflon-impregnated carbon fiber. In addition, the portable kit incorporates a four-liter aluminum air tank, which enables the system to run most air tools (it’s regulated to 150 psi). For the distinctly premium price, I wish the kit came with the ARB inflator that incorporates a dial gauge, rather than the simple clip-on chuck that is standard. But the waterproof case is strong, and the organizer pockets keep hoses and accessories neat—an underappreciated feature on expeditions where entropy nudges things toward clutter. The battery clamps are sturdy, the inline fuses easy to access if necessary, and there's a solidly mounted quick-release fitting for the air line next to the (lighted) power switch. You’ll know you’re dealing with a substantial piece of equipment when you pick it up—the whole package weighs 33 pounds, about as much as a Hi-Lift jack. The compressor alone weighs 19.4. 

If you prefer a built-in compressor (I normally do, but we haven’t yet decided on the final configuration in the Troopy), the air filters of the Twin can be relocated, rendering the entire unit submersible. ARB was not messing around when they designed this compressor.

The Twin is a significant investment ($830 for the kit; $520 for the compressor alone). But consider these two facts: 1) As stressed above, varying your tires’ pressures to suit conditions will do more than anything else to enhance your vehicle’s off-pavement prowess, your comfort, and the condition of the trail, and 2) Tire failure is by a significant margin the number one reason for breakdowns in the bush. With a high-quality compressor such as the ARB Twin you have both scenarios covered with professional-level ease.

The first rule of bush driving . . .

 . . . no matter if it's in Africa, South America, or Australia, is, you never, ever drive at night.

The second rule is, you always wind up driving at night. It's happened to us more than we care to admit, both through our own misjudgment or rushed scheduling and through circumstances we couldn't control (those bandits in Loliondo come to mind . . .). 

We just experienced the, er, former situation on our way from Port Augusta, on the southern coast of Australia, to Alice Springs, in the Northern Territory. The Stuart Highway is a good, fast (110 kph) road, but driving it in the daytime reveals the extent of the Kangaroo Karnage that goes on at night, when they are most active. And we had three hours of at-the-limit full-dark driving to do to get where we "needed" to go. It was a nerve-wracking drive with the ever-present risk of a large marsupial bounding across in front of us, and I especially don't imagine one wants to hit a kangaroo at the apogee of a jump.

Fortunately we had installed a pair of ARB Intensity AR21 LED driving lamps prior to the journey.

In the past I'd been wary of LED driving lamps, having tried too many that exhibited annoying color fringing or too-high color temperature, or spotty pattern. Not these—they displayed zero fringing, and the pattern, despite being the "spot" version, created a perfectly even flood of daylight far down the road and well onto the verge. This was not the typical UV scattering that fools one into thinking an LED light pattern is better than it is; it was genuine illumination, and my blood pressure stayed 20 points lower than it would have been without them. (The only downside, which is true with any driving lamp, is that when you flick them off for oncoming traffic it appears your vehicle's standard headlamps are now powered by votive candles.) 

The Intensity AR21 lamps are without doubt the best driving lamps I've used, eclipsing previous benchmarks such as the 130-watt IPFs on my FJ40, and even the legendary rally standard from decades ago, the Cibié Super Oscar. And the icing on the cake, of course, is that LEDs draw far less power than halogen lamps or even HIDs. I'll be installing them (or the even larger and brighter Intensity AR32s) on every 4x4 vehicle we own.

I'm tempted to say screw the aesthetics and bolt a set on the 911 . . .