4x4 Lockers: Better Traction For 4x4 Trucks - Get A Grip

This device, developed on an OEM basis by Eaton under the name EGerodisc, is a hydraulically operated, electronically controlled limited-slip that provides an optimal stability/traction solution at any speed. The next generation of this type of differential will have "torque vectoring" capability.

This device, developed on an OEM basis by Eaton under the name EGerodisc, is a hydraulical

Will Traction Control Make Lockers Obsolete?
On the newest 4x4s, especially SUVs, traction control is enhanced electronically, in some cases so well it might appear that adding another locking differential device would be unnecessary. These electronic traction control (ETC) systems work by applying braking control to a spinning wheel, thus transferring power to the wheel that has the most traction. Should a wheel lift while crossing a tree root, or a slick spot appear on a road or trail, these systems work automatically to keep the family SUV moving. ETC systems are popular because they're essentially free technology. Once you have four-channel ABS, you can add ETC at very little cost. So the question becomes, given the superb, seamless capability of the brake-based traction control system: Does anyone really need a traction-adding differential any more?

"It's fairly easy to demonstrate the limitations of any brake-based traction system if you challenge the vehicle enough," Eaton's Jeff Saxton said. "The problem is on those vehicles, if they're just using standard open differentials, there's nothing for the e-brakes to work against. ABS can apply brake to a spinning wheel, but that doesn't necessarily create enough torque across the axle to try and drive torque across to the other wheel that might have better traction. So while the braking can be effective for fairly moderate situations, the minute you start talking about off-road capabilities, it's pretty easy to demonstrate the limitations of brake-based systems."

As a rule, factory ETC systems can't take prolonged demand in a challenging situation, such as 100 yards of mud or a long, snowy driveway, without building up heat. "Most of those systems, if you tax it for more than a minute of time, it will go into a fail-safe mode and shut itself off."

That's the reason why manufacturers of SUVs that are intended to handle actual off-highway use, such as Jeep, Toyota, Land Rover, Hummer, and others, often add selectable electronic locking differentials to their 4x4s along with their traction control system. When the ETC gets overtaxed, the manual locking differential can still provide traction without heating up the brakes, and generally better torque transfer. Where no OEM equipment is present, an aftermarket device can be installed to provide the same function.

Another future technology, electronic stability control (ESC), is also complicating the future of locking differentials. When ESC becomes standard equipment in 2011, there is no guarantee enthusiasts will be able to slap in a mechanical locker without compromising a government-mandated safety system. Ironically, the advent of ESC has meant that the companies with OEM clients, like Eaton, will have opportunities to develop new business.

"Stability control is one of those areas of the industry that is as much of a challenge in terms of consumer education as it is in technology. If you really dig into that, you find out that a brake-based system is limited at the very best in terms of what it brings to enhance safety in a reactive system. If we're talking milliseconds, that may not be an adequate response. In terms of where the industry is going, there is the whole technology of torque vectoring--where you actually apply engine power as opposed to brake, to drive the vehicle into the intended path to try and mitigate an out-of-control situation. It takes a very special, fast-acting type of differential. We have a product we market under the name EGerodisc that can be modulated quickly enough to actually generate a combination of additions on both axles and transfer case to drive the vehicle in an intended path. I think you're going to see a lot more of that in the next few years. In the military, there is a huge awareness of torque-vectoring technology. It's incredible stuff, even to those of us who play with it every day. "