Differentials Explained - Limited Slip Differential

Differentials Explained - Limited Slip Differential

Limited slip differentials transmit equal torque to both wheels when driving straight. However, when one wheel spins due to loss of traction, a patch of ice, mud, too much throttle, etc., then the unit automatically provides more power to the wheel that has traction. Highly effective for daily driving and works well in rain, mud and snow. However, in situations where absolute lockup is needed, a limited slip is not the best choice due to the fact that limited slips do slip in some situations. An example of it slipping would be with one tire in the air. This does not provide enough resistance and the differential acts like it's open or standard counterpart. From the factory many Jeeps were equiipped with a Dana Trac-Lok limited slip units.  

Limited slips generally are a driven by a series ofclutch disc located behind the side gears. The different disc are held under tension with springs. As the slip increases the tension increases between the different layers of disc and provides resistance to limit the slip between the wheels. A draw back to this is that they need to be rebuilt as they do wear and their effectiveness diminishes over time. A special additive is also needed for the differential fluid to enable the clutches to work properly and to keep them from chattering during normal turns. 
 

Another form is using a gear drive that uses parallel axis, planetary helical cut gears inside the case provide a smooth and quiet automatic division of roque.  The gear driven limited slips such as the Detroit Trutrac often operates while being unoticed by the vehicle driver.  Under normal conditions the gear driven limited slips operates like a normal open differential.  The Trutrac can transfer 3.5 times more torque to the high traction wheel than a conventional clutch driven limited slip.  The torque is transfered by the pressure being exerted by the side gears and the helical cut pinion gears againts the case. This pressure then makes the high traction side turn with the ring gear giving the vehicle momentum to move. 

 Detroit Trutrac Gear Driven Limited Slip