Vehicle Running Gear

Open diffs, lockers, and traction control

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Many years ago I was exploring a trail in the mountains east of Tucson, Arizona, in my FJ40, and came upon a couple in a shiny new 4x4 Toyota pickup. They had managed to high-center the transmission skid plate on a rock ledge, so that the right front and left rear tires of the truck hung just an inch or two in the air and spun uselessly when the fellow applied throttle. The couple, new to backcountry driving, was bewildered that their “four-wheel-drive” vehicle had been rendered completely immobile by such a minor obstacle, and were convinced something was wrong with the truck. I picked up a fist-sized rock from the side of the trail and kicked it solidly under the hanging rear tire. “Try it now,” I said—and the Toyota bumped free. They were astonished and even more bewildered—until I explained how a differential works.

When any four-wheeled vehicle makes a turn, each wheel needs to rotate at a different speed because it travels a different line than the others, and thus a different distance. If, for example, the two rear wheels were locked together with a solid axle, the tires would scrub horribly every time the vehicle turned, and handling would be affected dangerously. Thus we divide that axle in two and connect them with a differential—a system of gears that transfers power from the driveshaft to the wheels while allowing them to rotate at different speeds in a turn. In a four-wheel-drive vehicle we add another driveshaft and differential at the front, so those wheels can be driven as well.

But an open differential, as this is known, has a major inherent flaw, especially for those of us who own 4x4s: If one tire loses traction, the differential gears, in effect, route all power to that side of the axle. Thus if you stop with one wheel on a solid surface and the other in mud—or hanging in the air—the tire with grip will remain stubbornly motionless while the other just spins. (Technically both wheels are receiving the same amount of torque, but the amount required to spin the low-traction tire is not enough to move the vehicle with the other tire.) So my friends in the Toyota pickup found themselves in a situation in which the power being delivered to the front axle was expended on the tire that was off the ground, while the same thing happened in the rear. Once I stuffed that insignificant rock under the hanging rear tire, the full torque of the engine was available and the truck pulled itself free.

Ironically, the drawbacks of open differentials became more apparent with the advent of so-called full-time four-wheel-drive vehicles such as Land Rover’s Defender. In a part-time 4x4, the front and rear driveshafts are locked together at the transfer case when four wheel drive is engaged, so power is always equally distributed to both axles and therefore to at least one wheel in front and one in back—but you cannot drive on pavement with four-wheel drive engaged or the tires will scrub and the gears will bind. The Defender (along with other vehicles such as the Mercedes Benz G-Wagen) allows engine power to be directed to both ends of the vehicle, regardless of the surface, by employing a third differential in the transfer case to allow the front and rear driveshafts to turn at different speeds on pavement and prevent binding. To ensure equal power to both ends of the vehicle on trails, the center differential can be locked manually. But if that lock fails—as happened to me in a Defender 110 on a remote route up the west wall of Kenya’s Great Rift Valley—you are left with a one-wheel-drive vehicle. When my front axle unloaded on the steep grade, all power went to that axle through the open transfer-case diff, and as soon as one front wheel unloaded I was completely immobilized with a single tire spinning fruitlessly—on a scary 40-percent grade with a steep dropoff. (I was towed the rest of the way up the escarpment when, improbably, a battered Land Cruiser appeared driven by none other than Philip Leakey . . .)

Over the decades, various attempts have been made to allow the differential to function properly in turns while maintaining full traction when needed. Way back in 1932 the engineering firm ZF, at the request of Ferdinand Porsche, invented a “limited-slip” differential to prevent the high-powered Auto Union Grand Prix cars Porsche had designed from spinning their inside tires when exiting turns. In the succeeding decades, many American manufacturers installed limited-slip differentials in their trucks to help enhance traction on slippery surfaces, and several types were developed. Some used clutch packs to transfer power, others (Torsen, Quaife) used gears, and some—especially those designed to be installed in transfer cases—used hydraulic fluid. 

But limited-slip diffs are just what their name implies—they cannot completely prevent loss of traction in challenging conditions. The best way to ensure full traction when it’s needed is to lock both halves of the axle together, thus ensuring ideal power delivery even if one wheel is off the ground. But once you do that you’re right back to our initial problem with tire scrub and gear windup. The trick, then is to have the differential lock only in conditions where it would be beneficial—or to have it locked all the time except when turning. This can be accomplished either automatically or manually.

In 1941 a fellow named Ray Thornton patented an automatic locking differential he called the  Thornton NoSPIN Differential. It was manufactured by the Detroit Automotive Product Corporation and installed in many WWII military vehicles. The NoSPIN employed a series of clutch packs and a spring-loaded cam gear, which kept the axles locked together unless the vehicle was turning a corner, when the cam disengaged the clutch packs from the spider gears and allowed the wheels to rotate at different speeds. In the 1960s American truck manufacturers began installing the NoSPIN in light-duty trucks as an option—and it gained its nickname, the Detroit Locker. While extremely effective, the Detroit Locker suffered from noisy operation on pavement as the gears engaged and disengaged, and handling that could sometimes be jerky as power transferred between one and two wheels. (Later models have attenuated these characteristics somewhat, but the transition is still noticeable to the driver.) A similar product made by the Eaton Corporation was introduced on 1973 General Motors light trucks, and Eaton subsequently bought the parent company of the Detroit Locker. 

The mechanism of the Detroit Locker and its relatives replaces a large part of the differential, requires precision resetting of pinion backlash, and is thus expensive and time-consuming to install as an aftermarket option. Not so with so-called “lunchbox” lockers such as the clever Lock-Right, which replace only the spider gears and can be installed in an afternoon by a competent home mechanic. The Lock-Right and its kin keep both axles locked together until the vehicle turns, at which point the internal drive plates ratchet past each other and allow the outside wheel to turn faster than the inside wheel. On the trail, full power is available to both wheels, even if one is airborne.

The Aussie Locker is typical of so-called "lunchbox lockers."

The Aussie Locker is typical of so-called "lunchbox lockers."

Opinions differ on the “lunchbox” nickname—some claim it’s because the unit will fit in a lunchbox, others because you can install one in the time it takes to eat a sandwich and chips (somewhat optimistic). Regardless, this type of locker is the most affordable and easy way to gain true diff-locking capability for your 4x4. However (there’s always a however), the Lock-Right-type lockers are restricted in strength depending on what the carrier is designed for, and are generally not recommended for tires over 33 inches in diameter. They can also be noisy on the street, as the ratcheting becomes noticeable around corners. And I would strongly dis-recommend them for installation in the front axle, as steering will be significantly affected (and, as with the Detroit Locker, they should never be installed in a front axle that does not have free-wheeling hubs).

Automatic lockers have their fans, but arguably the best locking differential is one the driver can control. The Australian company ARB popularized the air-activated locking differential after buying the rights to the Roberts Diff-Lock in 1987—and it transformed the capability of the Land Cruisers and Land Rovers in which it was first deployed. For most driving, a differential with an ARB unit installed acts as a normal open differential—no noise, no steering effects or increased tire wear. But when traction is lost—or, significantly, when the driver observes a spot ahead of the vehicle where traction might be lost—the locker can be engaged and the obstacle traversed smoothly and easily. Once back on a solid substrate the diff can be unlocked and returned to normal function. A small compressor (which can double for filling tires) activates the locker by pushing a sliding pin in the differential. The ARB locker is now available for a huge range of vehicles, and while its installation is as complex as that of the Detroit Locker (with the wince-inducing addition of needing to drill and tap a hole in the differential housing for the air line), its reliability and astounding capability has been proven over millions of miles.

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It took a few years, but vehicle manufacturers caught on to the benefits and capabilities of selectable diff locks. Toyota introduced an electrically operated rear differential lock in its TRD package for the Tacoma, and optional front and rear diff locks in the 70 and 80-series Land Cruisers. The Mercedes G-Wagen has front and rear locks, as does the Rubicon version of Jeep’s Wrangler, and the Ram Power Wagon, among other vehicles. Until you’ve climbed a 45-degree slope in a vehicle with both diffs locked—and, thus, true four-wheel drive—it’s difficult to imagine the gravity-defying traction available. Even experienced passengers gasp and scrabble for handholds as high-noon sun floods through the windshield. (Showoffs are advised to keep in mind that with the front diff locked steering is very difficult; it should only be employed when absolutely necessary and for as short a distance as possible.)

To explore the next step in making four-wheel-drive vehicles truly four wheel drive we need to do a 180-degree turn and look at . . . brakes: specifically anti-lock braking systems. 

While ABS has been around in one form or another since 1929, when a primitive mechanical system was developed for aircraft, it was Mercedes Benz that introduced the first fully electronic, multi-channel four-wheel anti-lock braking system as an option in 1978. ABS relies on a deceptively simple system of sensors at each wheel, individual hydraulic pumps for the calipers, and a computer control. The sensors do nothing more than count the number of rotations per unit of time for each wheel. When one or more of the sensors detects a wheel turning slower than the others during braking—as when a tires locks and stops rotating altogether, increasing braking distance and hampering steering control—the computer reduces braking force to that wheel, pulsing the pressure many times a second to maintain static friction between tire and surface. Soon this system was exploited to provide electronic stability control (ESC), to help road cars maintain traction in slippery conditions.

And then—lucky for us—a light went on in an engineer’s head that this system could also be used to enhance traction in four-wheel-drive vehicles. It’s accomplished by exploiting the characteristics of the open differential.

Recall the offside wheels on that poor Toyota pickup spinning helplessly in the air. With an electronic traction-control (ETC) system, those versatile ABS sensors send that information to the computer, which applies braking force to the spinning tire or tires. The open differential is “tricked” into increasing torque to the tires on the ground, and the vehicle pulls itself free. Land Rover debuted ETC on its 1993 Range Rover, and off-road driving has never been the same. Advances in programming and technology have since brought us to the point that some vehicles can maintain forward progress with traction to only one wheel.

That would be miraculous on its own, but engineers weren’t finished yet. One of the most challenging conditions facing a driver on trails is a steep descent. In an older vehicle such as my FJ40, if you stomped on the brakes in a panic on a steep downhill section, the unloaded rear brakes would lock and the vehicle would instantly try to swap ends. Descending such slopes meant using first-gear-low-range engine braking and careful cadence foot-braking to make it down safely. In a vehicle with automatic transmission (and thus little engine braking) the situation was even dicier. Enter hill-descent control: Punch a button, point the vehicle downhill, and steer. The ABS and computer can selectively brake individual tires if necessary to maintain a steady walking pace and prevent lockup on truly hair-raising slopes. No driver, no matter how skilled, can equal that.

I remember my initial experience in a vehicle equipped with ETC and hill-descent control. At first the chattering, juddering progress up and down steep ridges was alarming—it sounded like something was seriously wrong. But I soon got used to it and realized how effortlessly I was conquering obstacles that had required all my attention in the FJ40. 

Is electronic traction control, then, superior to manually lockable differentials? The definitive answer is: It depends. Remember that a skilled driver using manual diff locks can anticipate the need for extra traction and respond in advance, thus frequently avoiding drama of any kind. By comparison, a traction-control system must detect a difference in wheel speed before it reacts, and the computer must decide if action is required or if the driver is simply turning. In some vehicles I’ve driven a considerable amount of throttle—and trail-damaging wheelspin—is necessary before the system kicks in. Increasingly, however, manufacturers are incorporating driver-selectable, terrain-specific algorithms that quicken response when the vehicle is in low range, for example. These algorithms can also modify throttle response and shifting to suit conditions. Land Rover was a pioneer in this technology with their Terrain Response dial. Some vehicles, such as Jeep’s Wrangler Rubicon, incorporate both ETC and manual diff locks—the very best of both worlds.

The Nissan Titan XD's traction control will pull it through situations such as this, but not without some wheel spin.

The Nissan Titan XD's traction control will pull it through situations such as this, but not without some wheel spin.

One could argue that these computer-controlled tricks reduce the skill formerly required of the driver. Indubitably true to an extent—surely I feel I paid my dues with my leaf-sprung, open-diffed 1973 Land Cruiser over the years. Yet in the sybaritic, climate-controlled cockpit of a Land Rover LR4 or Jeep Wrangler Rubicon I can traverse terrain that would have the FJ40 struggling. If technology makes it easier for new enthusiasts to get out and explore the backcountry, I’m all for it—even if I don’t get to show off as often getting them unstuck with a fist-sized rock. 

The Holy Grail of FJ40 wheels and tires?

I’ve owned my FJ40 long enough to have gone through several generations of tire and wheel combinations. When I bought it it still had the factory steel 15 x 5.5-inch rims (with hubcaps), and absurdly skinny and short 215-series tires of a brand I do not recall, but which were genuinely tiny enough to hamper its performance on trails.

Santa Catalina Mountains, 1978

Santa Catalina Mountains, 1978

As soon as I could afford it I bought a set of then-de rigueur 15 x 8 white spoke steel wheels, and mounted larger Armstrong Norseman tires. Big improvement, although I could feel the increase in steering effort through the non-boosted box. At the same time I gave away those factory wheels and hubcaps—dumb move.

And there it stayed until the late 1980s, when I was starting to be aware of how things were done in other parts of the world. I became convinced that split-rim wheels were the absolute ultimate way to go—after all, you could break down a wheel and repair a tire anywhere, right? They were still standard equipment on Land Cruisers in Africa and Australia, right? So at some considerable expense I ordered a set of Toyota factory 16 x 5.5 split rims. When they arrived I was somewhat put off by their mass—they made the eight-inch steel white spokers seem light—but duly had mounted a set of LT 235/85 16 BFG All-Terrains. 

In short order two tire-shredding blowouts revealed that something was not right. It developed that the tire retailer had installed improper liners in the wheels. That was corrected, and despite shaken confidence I began employing the Land Cruiser as a support vehicle while leading sea kayaking trips from remote beaches in Mexico. And indeed it was true: I could break down a wheel and repair a puncture anywhere. Clients were impressed. Several times.

With a split-rim wheel and tubed tire, any puncture means completely breaking down the wheel to patch the tube. A nail hole that could be fixed in five minutes with a plug kit required 45 minutes of hard labor. The romance was wearing thin. By this time I was chalking up some experience in Africa with split-rim-equipped vehicles, and noticed a difference there. First—purely personal theorizing here—the economy of most African countries meant that random nails and screws lying on roads simply didn’t exist. They were too valuable. Also, the tires employed there are typically eight or ten-ply bias-belted 7.50 x 16 beasts that seem more or less immune to simple thorn punctures. I was experiencing fewer punctures on the back roads of developing-world countries—both in vehicles I drove and those in which I was driven while on assignment—than I was in the U.S. and Mexico.

African Firestone tire on a split rim.

African Firestone tire on a split rim.

By now I had replaced the three-speed transmission in the FJ40 with an H41, a four-speed with a low, 4.9:1 first gear. I thought that would allow me to install a slightly taller tire—and I was ready to dump the split rims and try alloy wheels. So on went a set of American Racing Outlaw II 16 x 7-inch wheels, and LT255/85 16 BFG Mud-Terrain tires. Given the two-inch OME lift on the vehicle, this was the outer limit of what would fit without clearance issues or ghastly body-cutting and cheesy riveted-on fender flares. Indeed at full left lock the left tire slightly contacted the steering box link. But otherwise the tires worked fine, and the combination stayed on for over a decade.

Still . . .

Two things began to nibble at my subconscious. First was the memory of those BFG All-Terrains in 235/85 16. So many things about the size seemed perfect. They were tall enough to noticeably benefit ground clearance, yet their narrow tread width made steering easy. Also, by this time the Land Cruiser had become something of a classic rather than just an old four-wheel-drive “jeep,” and I was kind of missing the whimsical look of those factory hubcaps. It would be easy to buy a replacement set of Toyota 15 x 5.5-inch wheels and hubcaps—but there was no tire size in BFG’s 15-inch lineup equivalent to the 235/85 16. For a while BFG sold a 9.5 x 33-inch All-Terrain that would have worked, but it was discontinued. Some owners (and, by now, professional restorers), were squeezing 31 x 10.5 All-Terrains on factory wheels, but those were not quite tall enough and not quite narrow enough to suit. (The size is also technically far too wide for a 5.5-inch wheel.)

What I needed was a 16 x 5.5-inch wheel with clips for the factory hubcaps—and out of the blue a few months ago my friend Tim Hüber sent me a link to exactly that, available from Japan. They were . . . expensive, eye-wateringly so. And would additionally need to be powder-coated a proper gray, adding even more expense. But it was exactly the Holy Grail for which I had been searching.

Ordered, delivered, powder-coated, mounted. And . . . indeed, perfect. The ideal all-around tire size for an FJ40, and the amusingly perfect retro pukka look, too. 

One genuine surprise: I assumed going to a steel wheel from an alloy—even with a smaller tire—would add significant unsprung weight. Not so. One alloy wheel and 255/85 16 Mud-Terrain tipped my hanging scale at 73.2 pounds. The steel wheel and 235/85 16 All-Terrain? Seventy four pounds even.

Never say never, but I predict this will be the final solution to the Land Cruiser’s footwear.

Left: 16 x 7 Alloy and 255/85 16 MT. Right: 16 x 5.5 steel and 235/85 16 AT. Same weight.

Left: 16 x 7 Alloy and 255/85 16 MT. Right: 16 x 5.5 steel and 235/85 16 AT. Same weight.

Now that's a proper suspension analysis

Our last trip to Australia and Tasmania, the first with all the modifications and additions to our Troopy completed, revealed some shortcomings in the suspension—no surprise with 180 liters of fuel and 90 liters of water on board, in addition to the cabinetry, pop-top, bumper and winch, etc. etc. It wasn't bad—the rear sagged perhaps an inch with everything aboard including us—but an inch is too much, and we could feel the shocks working hard to maintain control.

Daniel at the Expedition Centre in Sydney, who'd done all the work on the vehicle, had just one recommendation: A company called, humbly enough, The Ultimate Suspension.

TUS, as I'll call them, advertises "custom-built, fully integrated" suspension systems designed specifically for each vehicle, not just each model. After receiving the analysis above, I can't argue that their approach isn't thorough. I'm not sure what the percentages in the shock absorbers refer to—would 100 percent mean it's as comfortable as a Range Rover? Must ask. In any case it's interesting to see the weight at each corner and across the vehicle, and to know that (ahem, rather surprisingly) we're still safely under the Land Cruiser's GVWR, even with a full load of fuel and water.

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.

Building a zero-hour F engine

If you’re only going to rebuild an engine every 20 years or so, you might as well do a thorough job. That’s been the guiding principle for both me and my master Toyota mechanic and friend Bill Lee, as he disassembled and inspected the six-cylinder F engine and transmission of my FJ40 (see this post for background). Actually it wouldn’t have mattered whether or not it was my guiding principle—Bill would have refused to do it any other way.

The engine had been showing distinct signs of power loss, although oil consumption was not unusual. Teardown revealed one certain cause: the camshaft was badly worn, and on a couple cylinders was clearly not producing much lift on the intake valves. Bill’s explanation for this was illuminating. Apparently on start-up of an F engine, the cam is the last part to receive oil from the pump. Generally this is no problem as residual oil provides plenty of lubrication—unless the vehicle is parked for long periods, in which case the oil will drain away from the cam lobes. The cam will then be without oil for the first 10 or 15 seconds after starting. And—surprise—for several years my FJ40 has seen long periods of idleness while we were traveling overseas, using the Tacoma and Four Wheel Camper for journeys in North America, and putting miles on various long-term review vehicles. Shame on me. (Bill suggested changing to an oil from Joe Gibbs Racing that displays cling properties superior to standard oils. And driving it more.)

Once Bill had the engine disassembled entirely, he called and we had a chat. The cylinders were in excellent condition, still within specs, even still showing factory cross-hatch honing marks. The pistons came right out, Bill reported—no wear ridge at all. 

However. The bores showed vertical scoring, and Bill and I were pretty sure where this originated, as I’d discovered a surgical-strike rodent intrusion in the air cleaner last year, the cleaner itself chewed through and remnants of comfortable rodent accommodations in the housing. I cleaned everything out, but it’s likely some debris had been sucked into the engine in the meantime. (Mystery: After the incident I put hardware cloth over the opening, but Bill found the air cleaner chewed again. Either one got in during the day or two before I installed the screen—likely—or I had the Harry Houdini of mice.) 

The consensus from the machine shop was that the scoring could not be completely honed out while keeping the bore stock, so we decided to bore the cylinders and install new pistons, Japanese-made units from ITM (Toyota pistons are no longer available for the F engine).

The main bearings were in good shape, but given the need for machine-shop work anyway we decided to turn the crank and install one size over bearings. Bill also suggested balancing the components—not a huge deal given the inherent primary balance and even firing order of an inline six-cylinder engine, but every bit helps. The machine shop matched the weight of all the connecting rods to the lightest one by judiciously grinding away material on the caps. (Hey! Less weight means more horsepower!)

Meanwhile, the head has been given a valve job, and equipped with new OEM valve guides and springs—which Bill had to source piece by piece from several dealers around the country. Factory parts such as these are becoming more and more rare. The replacement cam is an aftermarket item; however, it’s a brand Bill has used before with good results. The lifters as well are aftermarket Japanese manufacture. (The last few new OEM F cam/lifter sets sold for near $1,000; this set totalled about $400.)

What else? Bill wisely recommended replacing the oil pump, even though it was working fine. Toyota no longer makes the F oil pump, but the (improved) model from the 2F is still available—however, installing it requires a 2F oil pan as well, so that is in hand. New OEM timing gears will ensure precise cam timing.

Once everything is put back together (with a one-of-few-remaining factory gasket kit), we’ll have an essentially zero-hour engine. It should in fact be better nick than when I bought the vehicle from its original owner in 1978, with 24,000 miles on it.

The header was in good shape, and so ceramic-coated for re-installation.

Next up for attention will be the H41 transmission and transfer case.

Cummins-powered FJ40

As a general rule I’m not a big fan of non-factory-original engine swaps. I’ve seen the results of way too many back-yard hackers bolting Chevy 350s into FJ40s, and Ford 302s into Land Rover 109s. (Not to mention American V8s implanted in Jaguar sedans and even vilely stuffed up the rear of Porsche 911s.)

Even when it’s done well, the result in an FJ40 seems less a Chevy-powered Land Cruiser than a Toyota-bodied Blazer, at least in my book—especially when the engine is coupled to a Turbo Hydramatic auto transmission. Yeah, more power and better fuel economy, supposedly, but the fuel economy often turns out to be chimerical from what I’ve heard first-hand, and unless you want to tow a boat or something, 250 or 300 horsepower in a 90-inch wheelbase seems like overkill. The torque curve winds up in the wrong place. And the lopey firing order just sounds wrong compared to the smooth burble of an inline six. 

With diesel swaps my other-maker prejudice diminishes somewhat, since we’re now looking at potentially significant fuel savings, and a torque curve working in the same region (2,000 rpm) as the gasoline F or 2F. True, I’d still prefer a factory Toyota engine—a 1HZ or 13BT would be a tempting replacement in my 40. However, I’ve seen other options done well.

All this is leading up to the photo you see above. It’s a 1977 FJ40 belonging to Steve Sency of Durango, Colorado, who accomplished one of the most strikingly clean engine swaps I’ve ever seen. Steve sourced a Cummins 3.3BT four-cylinder diesel that had been powering a generator at a cell tower site, and coupled it with an Orion 4:1 transfer case and an NV4500 five-speed (manual) transmission. Notice the braided stainless hoses where a vacuum booster for the brakes would normally be. Since diesel engines do not produce the vacuum inherent in a gasoline engine (because the air intake tract is always wide open), Steve installed a Vickers hydraulic pump on the accessory port of the Cummins. The hydraulic boost system now services the brakes and the power steering. 

Steve reports up to 23 mpg at 60 mph (@2,000 rpm), which, given the roof tent, dual 12-gallon water tanks, and auxiliary fuel tank on the vehicle (not to mention the drag coefficient of the FJ40, roughly equivalent to that of a three-bedroom house), is pretty impressive.

Steve's wife, Linda, enjoying a perfect campsite.

Update: After several requests from readers, Steve sent a few more photos of the engine.

Even TLCs need TLC now and then

In 38 years, the 1973 FJ40 you see above has, with the exception of dead batteries, never once failed to start and run and get me where I wanted to go. The closest it came was just a couple of years ago, when crud in the carburetor meant I had to clean the float bowl before it would maintain an idle. And one time, in Mexico's backcountry, the combination of a dead battery and bad gas forced me to replace the fuel filter while the engine was running. Scant glitches in an almost unbelievable record of reliability. 

Still wearing most of its original paint, it also retains its original ring and pinion gears; until a couple of years ago it still had its original starter—a record of longevity I've never come across before. The front and rear side marker lamps? Original Toyota factory bulbs, all four of them, still burning 43 years after they were plugged in on the assembly line. Weird.

Now on its second F engine, in the last couple of years I noticed a significant loss in power, and inspection revealed low compression in one cylinder. At the same time, the H41 transmission and transfer case have been getting louder and louder with wear, also betrayed by significant slop when lifting off the throttle. So it's time for a bit of refurbishment, care of our master Toyota mechanic Bill Lee, formerly of Tucson but who infuriatingly keeps moving farther away from us, now 500 miles off in Farmington, New Mexico. Recently he called and said he had another FJ40 being trucked to him from southern Arizona, so we added ours to the shipment.

Bill is planning to install new piston rings and a new cam, do a valve job, and go through the transmission and transfer case. Anything else he notices he'll take care of as well. It will be a new lease on life for a loyal machine. 

I know what you're wondering: I paid $3,500 for this Land Cruiser in 1978 when I purchased it from the original owner. Since it's now worth several times that despite 300,000-plus miles of use, it's safe to say it was a good investment, no?

Early days. Three Feathers in Redington Pass

Leading sea kayak tours in Mexico

Why are there oranges in my tires?

 

 

 

You’ve no doubt seen racing drivers on a warm-up or yellow-flag lap weaving from side to side to keep their tires warm. The reason is that the rubber compound in race tires is formulated to be at its stickiest at race speeds and elevated temperatures. At cooler temperatures it quickly hardens and loses grip. 

You could fairly state that designing a racing tire is simple compared to designing a tire for a street car or SUV. The racing tire only has to last long enough to finish the race, and often not even that long. Fuel economy is well down the list of priorities; ride comfort and noise aren’t even on it. 

Not so with a street or SUV tire. Consumers want it all: long tread life and superior cornering traction, high fuel economy and safe braking performance, good off-pavement traction and low noise on pavement. A bunch of mutually exclusive characteristics. As you can imagine, a tread compound hard enough to last 40,000 or 50,000 miles and exhibit low rolling resistance to save fuel has a difficult time also providing above-average cornering and braking traction. Thus since the dawn of pneumatic tires manufacturers have juggled rubber and petroleum compounds to arrive at the best compromise for the application.

A few years ago Yokohama threw a new ingredient into the mix: orange oil, which, just as its name suggests, is derived from the oil in orange (and other citrus) peel—the specific compound desired is called limonene. Why citrus oil? One reason is to save on petroleum, of course, making the tire more “green.” But Yokohama claims a far more immediate benefit. According to the company, the tread compound in a tire constructed with limonene has the ability to instantly change viscosity in response to temperature. During normal driving the viscosity is high, resulting in low rolling resistance and long tread life. But during braking or cornering the viscosity shifts to a more sticky state, enhancing grip.

Proving or disproving this through independent testing might be difficult, since Yokohama does not offer otherwise identical tires with or without the orange oil technology. Most likely only a long period of consumer feedback and real-world tread-wear results will show if the concept is sound or just a marketing gimmick. The company gave me a set of the new Geolandar AT GO15 tires for our Ford F350 pickup, and so far they are performing excellently, with decent off-pavement traction and fine on-road characteristics. I just towed a 9,000-pound trailer full of Overland Expo equipment across the country, and had zero issues with handling or braking—including a couple of abrupt maneuvers to avoid insane suicidal drivers on the freeway through Dallas at rush hour (not fun at the wheel of 15,000 pounds worth of kinetic energy). The tread still appears within new specs, so I won’t be surprised if they last the full 50,000 miles promised by the guarantee. (The lighter-duty P/E Metric versions of the tire have a 60,000-mile warranty.)

I can’t find any other manufacturers using orange oil technology yet. I’m not sure if this is because Yokohama has managed to protect their use of it, if the others are sitting back to see how it goes, or if they are frantically testing their own citrus concoctions. Time will tell.