A Dana Spicer differential is part of the axle assembly for rear-wheel and two-wheel drive vehicles that allows each tire to rotate at different speeds to improve handling and control. The differential refers to the assembly that includes the axle shafts, ring and pinion, carrier, spider gears or posi-traction unit. When a vehicle turns or traction is lost, the spider gears within the carrier of a Dana Spicer differential engage, letting the tires spin at different speeds.
A standard open Dana Spicer differential consists of two-axle shafts, a ring and pinion, a carrier case and spider gears inside the case. The spider gears shift power to the tire of least resistance, such that if one tire is on ice or stuck in mud, it spins increasingly faster while the other remains motionless. This can lead to differential failure. The standard open differential is designed to allow tires to rotate at different speeds when negotiating turns and be unnoticed by the driver.
A Dana Spicer differential with a Dana Spicer TracLoc or PowerLock posi-traction unit provide partial lock up, or limited-slip, differentiation. Using a series of clutches and springs, along with the spider gears, a posi-traction unit prevents a complete loss of traction to either tire. Using mechanical pressure, when one tire begins to spin faster than the other by a preset amount, the clutches engage, sending power back to the tire that has retained traction. This helps prevent complete spin outs on ice or in mud.