Four wheel drive (4WD) is the most common concept in increasing traction. In a 4wd system both the front and rear axle receive power. It is common for base-model 4WD vehicles to have “open diffs” (see below). While it has definite benefits, 4WD generally costs more to purchase, insure, maintain, and lowers MPG.
In trucks and cargo vans a two wheel drive (2WD) vehicle only receives power at one axle, usually the rear axle.1).
All Wheel Drive (AWD) is a usually a full-time system found in cars and light SUVs.
The usual type of stock differential is an open differential, a simple arrangement that is inexpensive and works well on surfaces with sufficient traction. The problem is that when traction is not always sufficient; in those situations one tire spins, one tire is stationary, and the vehicle is stuck.
One way to meet this challenge is to use a locking differential (LD). A locker can be changed, electronically or by air pressure, between two states:
Another way to meet the challenge is to use a limited slip differential (LSD), whether physical or virtual. A physical or traditional LSD uses clutch packs or worm gears to limit the difference between wheel speeds. A certain amount of spinning of one wheel relative to the other results in a clamping effect which can either lock them together or limit the difference, as in a torsen type LSD. Some GM vehicles came stock with a clutch type G80 limited slip; a VIN decoder or vehicle info tag will reveal this information.
The sensors and controls associated with ABS brakes allow for virtual forms of limited slip. A subset of Electronic Traction Control (ETC), Brake-lock differential (BLD) can control wheelspin with an otherwise-open diff by selectively braking the wheel that is spinning. In addition to stability controls that will not be addressed here, many ETC systems can be configured on the fly:
Tires on the drive axles can make a major difference on a vehicle's ability to reach secluded camping spots. All terrain tires favored on CRVL are: