n the last 10 years, significant changes have been occurring in the world of four-wheel drive—some good and some maybe not so good, but all are heavily researched and explored by huge numbers of engineers. Typically, these engineers and driveline teams have had to create their own technology or simply deal with the big boys such as New Venture Gear and Borg-Warner. However, with the growing number of companies selling and manufacturing trucks and sport/utilities in the United States, especially those equipped with four-wheel-drive systems, the Society of Automotive Engineers (SAE) decided to hold its first TOPTEC (TOPical, TEChnical) Workshop on the innovations of four- and all-wheel-drive systems. Companies such as Dana/Spicer, New Venture Gear, Eaton, Tractech, Boeing, and Borg-Warner presented technical and informative material about their new and future products. And you can bet many of the audience members included representatives from Ford, Chevy, Jeep, Land Rover, Isuzu, and others.
With the exception of the Unimog, which seems to be the only vehicle on the planet without a single compromise, manufacturers typically decide between pavement and trail bias. Rare is the vehicle that can do exceptionally well in both arenas. However, for those manufacturers that want to keep true trail capability, the split seems between employing computers to make most of the decisions (Land Rover Discovery, AM General Hummer, and Mercedes-Benz ML 430) and offering some type of internal, mechanically driven pump/plate/geardrive to do the biasing or locking (Grand Cherokee, Toyota Land Cruiser, and Silverados). Whatever the choice, we’ve discovered a vehicle’s true four-wheel-drive personality can be most easily revealed by exploring how a given manufacturer deals with the issue of traction.
There are many options for domestic and import four-wheelers to improve trailability (e.g. traction). Some of the following products are available on ’99 vehicles, while other technology is scheduled for future release and still others are in the theoretical stages of development.
ASHA Technologies has been getting plenty of media attention with its contributions to the new Grand Cherokee four-wheel-drive system. The combination of a gerotor pump and a pressure-sensitive clutch plate has created quite a stir in the world of traction. Specifically, Dana/Spicer and New Venture Gear have aligned with ASHA to include those locking differentials in the front Dana 30, rear Dana 44, and NVG 249 transfer case to create a rarity—a true four-wheel-drive traction monster Jeep calls Quadra Drive. Additionally, ASHA is looking to license the limited-sliplike locking differential to other manufacturers for all-wheel-drive and front-wheel-drive systems all around the world.
Benefiting from its own recent success with the huge Silverado launch, Eaton is back to getting torque where it’s needed—the wheels. The Command-Traxx is technically a limited slip, acting like an open differential during high-traction driving, but it provides full axle lockup when wheel slip occurs. Through a series of plates made of lifetime materials, the sensitivity can be adjusted. The Command-Traxx is being used right now in Silverados and many other GM trucks. Coming soon is an electronically selectable locking differential, looking to compete with ARB’s push-button Air Locker. Although Eaton sources will neither confirm nor deny that we’ll see these on new trucks soon, we’ve heard several OE manufacturers are interested in offering it as part of a rugged off-road option package.
Developments in transfer cases seem to be marching along at the same pace as differential tech. Both New Venture Gear and Borg-Warner have super sophisticated technology in their latest and greatest transfer cases. The NVG 247 transfer case, called Quadra Trac II by Jeep, incorporates some of the same locking differential benefits between the two driveshafts that the Vari-Lok differentials (basically gerotor-pump technology) offer between the two axles. The result is instantaneous traction where it’s needed, without the use of complex computer modules and sensors. However, the NVG 246 transfer case in the new Silverado does offer quite a bit of electronic complexity, with the most substantial benefit being a wide range of versatility. The NVG 246 uses multiple sensors and a dedicated four-wheel-drive computer to allow for two-wheel drive, all-wheel drive with a rear-wheel bias, four-wheel high with a locked center differential, neutral, and four-wheel low range with a locked center differential. Obviously, for most drivers the versatility of a system like the new Silverado’s has incredible potential. If nothing else, it offers a solution for just about any stuck problem you can think of. However, don’t think Borg-Warner doesn’t have an answer as well.
Possibly the most technically sophisticated transfer case sold in the United States today sits at the center of one of the most visually high-tech sport/utes sold. The spaceship-looking Isuzu Vehicross (as well as the Isuzu Trooper and Acura SLX) uses a Borg-Warner 44-22 Torque-On-Demand full-time four-wheel-drive system. The beauty of this computer is that it can change the shift points of the transmission depending on high or low range, can monitor any one of the numerous input variables about 200 times a second, and can even anticipate. Based on what the vehicle has been doing and is doing, sensors predict what is going to happen then adjust power distribution to counteract the anticipated loss of traction—sometimes stopping a slip before the driver even knows it is about to occur. As impressive as this auto-focus technology is, possibly the best feature of the B-W 44-22 is the dash display, informing the driver at all times of what each tire is doing, tractively speaking. LED readouts display where and how much slippage is being detected, then presumably before the light from the display reaches your brain, adjustments have been made to keep things smoothly moving along. With something this high-tech, we like the idea of being able to monitor it—seeing what we’ve paid for, so to speak.
But this isn’t everything. We’ve only highlighted a few of the existing technologies that were presented at this particular conference. The true visionaries in the world of four-wheel-drive and all-wheel-drive technologies seem to think magnetic and electric trail rigs will eventually be heading our way, offering unlimited torque and gearing potential as well as green-friendly benefits.
Naturally, we’ll continue to have stories coming out about improving traction, and it seems clear that some of the brightest engineers in the world feel this topic deserves considerable thought. We have no doubt that more impressive technology—for both hard-core four-wheelers and daily all-wheel-drivers—is just ahead. And we’ll be here to pass it along.