Extreme use for the average consumer may amount to a midsummer trip to Vegas. Granted, the tarmac may shimmer with heat, but it's a smooth surface. While the speed limit will most likely be broken at some point, that still won't approach the 140 mph of Trophy-Class trucks competing in a SCORE race in Baja. The combination of high speeds and varying terrain makes a Baja race a natural for OEM extreme-use testing.
A case in point: Jamal Hameedi, Ford engineer and product manager for the TorqShift transmission, estimates that the 500 miles of desert racing his truck recently went through is the equivalent of 50,000 on-highway miles. "Clutches are black magic to most people," says Hameedi. Small wonder: The TorqShift has six internal clutches working in conjunction with the planetary gears to give different ratios and different gears. "These clutches don't work in progression. They work in conjunction, but don't provide a step-by-step through the gears as you might expect," Hameedi adds. For the engineers, a race always starts when the previous one ends. Constant refinement goes on in the Trophy Class and, for many, money is no object. Hameedi insists Ford was in Baja to find "root-cause fixes rather than symptom fixes."
However, not all of the teams were there to test products for manufacturers. Like many, the Terrible Herbst team races to win. Whatever the motivation, all teams must refine their cars with each race. Wally Kaiser of Advanced Machining Dynamics in Highland, California, worked with the Ford team in the past, but most recently helped redesign the Herbst transmission. The Herbst car is four-wheel drive, which Kaiser says is a departure from the norm at Baja. He notes, "Four-wheel drive is expensive, makes the car heavy, and gives it more reasons to break down." Hameedi adds, "The more weight you have, the more impact is transferred to expensive parts like axles and ring-and-pinion gears."
Regardless, Herbst was a strong contender. Kaiser was confident the experimental six-speed dog-ring differential and constant-mesh transmission would help the Herbst car stay together. The clutch has an air motor for starting and a joystick to make full use of the constant-mesh gearing. In a race like Baja, where refinements must add performance and dependability, it's the latter that's most important. For Hameedi, everything he learned in Baja will translate into a better product for Ford customers.
On the other side of the two- versus four-wheel-drive debate is the TorqShift Team, whose Trophy truck has F-150 skin and a two-wheel drivetrain. Hameedi is happy with the way things are, while Kaiser seems to think Herbst's primary gear ratios have allowed for the inclusion of strong ring-and-pinion gears in the differential and isn't worried. Five hundred miles of desert would tell the tale.
At the Baja 500 last year, Ford looked hard at the TorqShift transmission; the company tried to break it to find its weak points and make it better. The TorqShift's torque converter is a hydraulic torque multiplier with a lockup clutch, which can bypass the hydraulic clutches if need be. The racing TorqShift has six internal clutches compared with five in the street model, but in all other respects is identical. The computer chooses the clutch based on a variety of circumstances, including driver behavior and road conditions. Torque requirements are customized to meet the constantly changing needs of the vehicle. The computer also controls hydraulic pressure, converting locked differentials to active, allowing the wheels to turn at different speeds to provide traction where needed.
With this complexity comes the need for intelligent, highly efficient lubrication. And this is where problems developed during the early stages of the race. At checkpoint two (Serro, Colorado), an hour into the race, the transmission was running at 290 degrees. Dave Oho, program coordinator for the Ford team, felt the TorqShift wouldn't last long above 250 degrees. "The filters and seven electric solenoids start to wilt after too long at those temps," Oho says. Hameedi and Oho were worried. At checkpoint three, the pit crew found fluid between the seals, but the transmission wasn't leaking. Hameedi was more confident, knowing he wasn't losing precious cooling to a leak. Mike Bakholdin, the crew chief, was considering taking the shroud off the transmission coolers, hoping that would lower the temperature about five degrees.
Hameedi theorized the problem may be pump cavitation: "Cavitation can cause fluid to funnel and suck air. This'll create fluctuations in pressure and cause the oil to miss certain key areas." At this point, the team was 11 minutes off the lead. The lead Trophy truck was Herbst. It was a two-way competition at this point, one no one wanted to lose because the transmission was hot. Between onion and wheat fields, with the mountain leg coming up, Dan Smith, one of two drivers in Ford's team, said he would take the chance and run at 90 percent of maximum rpm, hoping the temps in the mountains would help cool the vehicle and give Dave Ashley, his partner, a chance at a strong finish. After the Trinidad pit stop, the transmission cooled to 235 degrees and everyone's mood lightened. Half an hour later, the temp was back to 290, the mountains still a long way off.
Smith radioed: He lost his alternator when the bolts sheared off. Two hours later, his team found him in the outback and he was on his way again. Herbst, ahead of Smith, stalled in a Tech Inspection site, with ring and pinion problems. Both trucks got fixed, but by race's end, neither was the winner. Hameedi shipped the transmission back to Detroit for teardowns.
At headquarters, the teardowns uncovered transmission-pump problems. Hameedi was confident they were the source of the overheating. "The clutches were being applied inadvertently when the spinning inside the transmission caused the lube to apply pressure to them. At the same time, there was uneven lubrication. We created a leak path to allow some of the fluid to exit at high rpm and allow the clutches better lubrication and performance," says Hameedi. The lubricating pump on the TorqShift was designed for a diesel application, meaning a low-speed/high-flow operation. Hameedi and his team adapted the pump to a high-speed/low-flow operation, more typical of gasoline vehicles. That allows the clutch to spin faster and with more even lubrication. "We retoleranced the pump gears and slightly reduced the capacity of the pump to better match the higher-rpm duty cycle," Hameedi reports. He also says the new torque converter developed for the race looked flawless when cut apart. Meanwhile, the Terrible Herbst crew will be stiff competition in future races, once they figure out whether the added weight of four-wheel drive is worth the risk of differential failure during a big race.
How the Big Boys Play
by Tim Barton
Trophy trucks are the big boys of Baja, a race in which everything from motorcycles, quads, and dune buggies compete. The Trophy teams are run with military precision and support. The TorqShift truck, like the Herbst truck and others, had a huge tractor-trailer that served as a mobile repair station and parts-supply warehouse. In addition, most teams have chase vehicles at various points along the track. The Ford team had nine chase vehicles in all, with radio communications to the race car.
Helicopters relayed instructions to the race car, informing the driver if, for example, the chicken truck on the tarmac had passed the point where he'd be coming down off the goat trail onto the highway. Civilian traffic often presents a major obstacle to racers. The highway remains open, despite the fact that many miles of it are actually part of the course. Fans wander on and off the course, seemingly oblivious to the whine of approaching vehicles as racers pass each other in an attempt to hit the next off-road section first, ahead of deep, dark clouds of dust. This year's winner was a buggy, rather than one of the high-horsepower Trophy trucks.