OPEN CARRIER
    The open carrier is a stock replacement and works well for the guy who wants to save money and rarely goes off road. This means that it corners well, but does poorly in the trail traction department. Typically, you won't need a new one unless you change gear ratios.

TRAC-LOC
    The Trac-Loc is a stock replacement limited slip unit. It is fairly inexpensive and easy to rebuild. It is a clutch-type unit and will not lock up 100 percent. When one tire is off the ground it will spin freely just like an open carrier. However, if you apply a little brake pressure the unit will usually start turning the grounded wheel. This trick works because it loads the clutches and engages the unit. The Trac-Loc is a light-duty limited slip and will not hold up under extreme off-road conditions. If the unit wears out it can ussually be rebuilt. Trac=Loc units feature a one-piece case and two side gears.

POWER-LOC
    The Power-Loc is similar to the Trac-Loc, but is a more heavy-duty unit. Like the Trac-Loc, it is a clutch-type limited slip. It uses floating cross shafts that ride on a ramp in the differential case. When power is applied, the shafts ride up the ramp and load the clutches for a more positive engagement. While it doesn't lock up 100 percent, it is a very aggressive and durable limited slip. Power-Loc units feature a two-piece case and four side gears. This unit can be rebuilt, and by stacking the clutches differently, you can vary the slip percentage to make it more effective on the trail or less harsh on the street.

TRD POSI
    The TRD, or Toyota Racing Development, posi unit is a good clutch-type posi that works well on the street, as well as in snow and mud. However, it is not recommended for "hardcore" rock crawling. TRD Posi units are only made for Toyota applications.

TRUE TRAC
    The True Trac is an all gear driven posi. It has a smooth transition from engaged to disengaged. A True Trac will not lock up 100 percent, but is a little better than someclutch-type units. A True Trac doesn't chatter or pop in corners like a full locker or clutch-type posi unit can. Best of all, it doesn't have any clutches to wear out. True Tracs work well on the street and even better in snow and mud, but they are not recommended as your only traction aid for hardcore wheeling. They do make a nice unit for the front axle on the occasional trai rig.

LOCK RIGHT and E-Z LOCKERS
    The Lock Right and E-Z Locker are true lockers that replace the side gears in the stock carrier. They are intended for the person who wants maximum traction for occasional hardcore off-roading but who spends more time on the street. Both units are good lockers and with 100-percent lockup will serve you well on the hardcore trails. The drawbacks to these units ( as with all true lockers) are questionable performance on icy, off-camber roads and reduced tire life. These types of units tend to be noisy and twitchy when cornering and take some getting used to. They also tend to clunk and bang much lid the old-style Detroit Locker. The weak link with these lockers is the stock carrier, which is limmited in its torque capacity.

DETROIT LOCKER
    The Detroit Locker is the granddaddy of them all. It is an auto-locking differential designed for extreme duty. It handles massive torque and is the choice of most serious four-wheelers and racers because of its nearly flawless track record. The detroit Locker will lock up 100 percent. It also produces some noise and twitches as it locks and unlocks. However, the newly designed Soft Locker has significantly reduced nois and freeplay, making it more livable for those choosing to use it on the street. In terms of drawbacks, icy off-camber roads are more difficult to negotiate and tire life is reduced.

ARB AIR LOCKER
    The ARB Air Locker is a fantastically designed locking device because you can control it from the driver's compartment. You can lock and unlock the unit whereever you wish. When you are on hardcore trails you can flip the switch and an air pump activates the locker. When the unit is engaged you have completely locked axles just like a spool. Another great advantage of the ARB is that it can be unlocked on icy roads to act as an open carrier. An open diff works better than a locked unit on ice since one tire acts like a rudder to steer you straight. Also, tire life is not shorteded as much as with conventional lockers because you lock it only when you need it; in street driving, the diff is usually unlocked. The disadvantage of an ARB is that it requires an air compressor, electrical wiring and plumbin ( air lines) to operate. These are additional items that raise the initial cost and could possibly fail when you need them most. So, preventive maintenance is a must and spare parts are a necessity.