2007 Mercedes GL-Class Owner's Manual - Page 207

Controls in detail Differential locks* For more information on Off-road driving, see "Off-road driving" ( page 357). Vehicles with enhanced off-road package* are equipped with automatic locks for the center and rear axle differential to improve vehicle traction. The center differential compensates for differences in wheel rotation between the front and rear axle. The rear axle differential compensates differences between the rear wheels. A few words about differentials and differential locks* When a vehicle negotiates a turn, wheels on the outside of the curve must travel farther and rotate faster than the inside wheels. The differential, the operation of a set of gears that allows the powered wheels in a vehicle to turn at different speeds, makes this essential function possible. The drawback is that the differential also sends most of the engine's power to the wheel with the least load or strain on it. For example, if one of a vehicle's powered wheels sits on a patch of snow and spins because there is no traction, all of the engine's power will go to that wheel because the power will take the path of least resistance. Meanwhile, the opposite wheel, sitting on dry pavement where it could get enough grip to start the vehicle moving, sits idle because it receives no power. The Electronic Traction System (ETS) addresses this problem and provides for good control and steering ability by automatically slowing the slipping wheel and thus increasing the power to the other non-slipping drive wheels to get the vehicle moving. The ESP® and ETS in this vehicle feature such intelligent limited-slip differential technology, ideally suited for on-road and light off-road driving. Transfer case position LOW ( page 203) also enhances off-road driving capabilities ( page 357). More extreme off-road conditions may call for another solution, engaging a differential lock or preventing the differential from operating altogether. This vehicle comes with two differential locks: transfer case (center) and rear. Each can be engaged simply by operating a rotary switch located on the center console ( page 207). When the transfer case (center) differential is locked, the combined (or average) speed of the front wheels is identical to the combined rear wheel speed. When the rear differential is locked, both rear wheels turn i At the front axles, the 4-ETS system ( page 109) compensates for any traction problems. 206