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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:
Airing down tires in soft terrain can help increase traction.10),11) You may want to procure an air compressor before you need it so you can air your tires back up afterwards.
Airing down works because:
In sand, airing down to pressure of 12-15psi is common, with some going down to 8psi. When aired down dramatically use gentle throttle inputs so you do not spin the tire off the wheel or cause other damage.
In loose rock, air down somewhat less so the sidewalls are less likely to be damaged by sharp rocks.