$100 Trac-Lok Limited-Slip Rebuild

Cheap Traction

Brian GabrielPhotographer, Writer

There are three main categories of axle differentials: open differentials, limited-slip differentials, and locking differentials. They are all terms we have heard before while cruising the web forums or reading our favorite Jp Magazine issues cover to cover. In general, a differential is the mechanism that splits the power to the left and right tires at either the front or rear of the vehicle. It allows the wheels to travel at different speeds when cornering, since the tire on the outside of the turn must travel a longer distance than the tire on the inside of the turn. Most differentials from the factory come with an open-differential configuration. With this setup, the power is routed to the tire that has the least amount of traction, which can tend to be a problem when exploring off-road in certain terrain and conditions.

Locking differentials are on the other side of the spectrum. Automatic lockers can be a full differential replacement unit, like a Detroit locker. Or a lunch box–style locker that replaces the spider gears inside of the factory differential case. They both function the same in that when power is being applied to the differential, it will equally split the power to both tires. This will force both tires to power the Jeep in any situation, such as turning the tire that has traction when the other tire is slipping in the mud. Lockers also force the tires to rotate at an equal rate when cornering. This can cause the tires to “chirp” when making a turn on the pavement, reduce turning radius, and result in some overall quirky road manners. While off-road traction is increased, street driving manners are sacrificed.

There is some middle ground though in the form of a limited-slip differential. A limited-slip differential has typical spider gears found in open differentials. However, clutch discs are added to the side gears to create some friction bias to transfer power to the tire that has the most traction. By no means does a limited slip perform like a locker, and beware of manufacturers that refer to limited slips as lockers. In heavy off-road terrain and rockcrawling, a limited slip will leave much to be desired. Limited slips are excellent for wet, slippery, sloppy, or snowy terrain, especially basic mountain roads and Forest Service roads. They provide additional traction over an open differential while maintaining very friendly street manners.

There are several different styles of limited slips available through the aftermarket, and some are priced similarly to many of the full lockers on the market. Like most folks, we need to do this whole Jeep thing on a budget. Luckily, many limited slips were offered in Jeeps, trucks, and other SUVs from the factory. The clutch discs do wear out after a while and require some servicing to be brought back to their full original function. Follow along as we freshen up one of these factory limited slips and show you how to bring them back to life and working like new.

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