A differential is a specialized gear system with one input, the drive-shaft, and two outputs, one to each wheel. A differential allows the two outputs (wheels), to turn at different speeds. This is important when turning because as you turn the distance each wheel has to travel is different, but that distance must be travelled in the same amount of time. Without a differential a great amount of stress would be placed on the drive-system and would either cause damage or cause one wheel to lose traction by slipping.
Types of Differential
- Open differentials work as described above, this is the most common type of differential found in cars and trucks today. An open differential will allow for either wheel to have anywhere from 0% to 100% of the available power by sending more power the which-ever wheel has less resistance, this can be a problem in low traction situations such as when one wheel is in mud and the other is on gravel. The wheel without traction in the mud will absorb all power stranding the vehicle.
- Limited Slip differentials use either passive means, such as springs in the differential to creative artificial resistance, or active means like a computer controlled hydraulic system to limit the amount of power that will be allowed to sent to each wheel. By doing this it can be either made less likely or guaranteed that a wheel with traction will not lose all power. The mechanisms that operate a limited slip are more likely to wear out than any other type of differential, however.
- Locked differentials will always send 50% of the available power to each wheel. There are several sub-categories of locked differential.
- Automatic lockers, generally referred to as auto-lockers, work in several different ways. One way is by allowing either wheel to spin faster than the drive shaft is spinning it, this allows turns to completed similarly to an open differential. Other auto-lockers use mechanical devices to sense that the vehicle is turning and act in a pseudo-open fashion. Auto-lockers are typically less expensive and easier to install than other lockers.
- Welded, often called Lincoln or redneck, lockers refer to open differentials that have been welded solid so that it acts like a locker. These should never be used in a vehicle that will touch pavement as the force exerted on the differential while turning can be so great as to cause the differential to rip itself apart, often taking the entire axle with it. These are not recommended for any vehicle you may depend on.
- Selectable lockers are electric, hydraulic, or vacuum activated lockers that can be turned on or off. While turned on the axle will be fully locked and when off they will act like an open differential. These provide maximum flexibility for a vehicle that will be on and off-road, but they are much harder to install and significantly more expensive than other types of lockers.