If you are looking for true traction on the trail, then dispense with flexy suspension systems and upgrade your differentials to the Truetrac or Detroit Locker. Traction differentials are by far the greatest traction-enhancing devices you can install on your vehicle. In addition to providing you with added traction on the trails, the Truetrac and Detroit Locker differentials are considerably stronger than the stock differentials, both in the internal components and the carrier. Because the Truetrac and Detroit Locker do not require the added complication and cost of switches, solenoids, relays, pressure switches, air compressor, and air lines, they are extremely reliable and cost-effective. No alteration to the third member is required as with the ARB Locker.

All differentials depicted below have new Timken bearings pressed onto the carriers. We recommend the fitment of new carrier bearings for all replacement differentials as the factory differential bearings are usually not concentric. Furthermore, removal of the carrier bearings is time-consuming and may damage the bearings. We believe that it is far better to press on new carrier bearings with every replacement. Cost of the pressed-on bearings is only $50 per differential.

Tractech Truetrac Front Differential (912A407) $620

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Bearings are included in the above price

This limited slip differential will not permit one wheel to spin uncontrollably while the other sits stationary. Rather, the Truetrac always distributes some torque to both wheels. On the trails and on the road, the Truetrac will permit you to steer the vehicle exactly where you want. The Truetrac is a drop-in replacement for the weak open differential on all Discovery Series I's and II's, Range Rover Classics from 1994 to 1995, and all Defender 90's. The Truetrac requires no special lubricants for proper operation. Most limited-slip differentials are clutch operated and require special friction modifiers for optimum performance and the clutches wear out with use. The Truetrac, however, is a gear-operated design and requires no special lubricants for proper operation. Furthermore, the gears do not wear any faster than the gears on the open differentials. The Truetrac also makes the vehicle want to track very straight, solving the loss of caster problem on lifted vehicles without the attendant driveline vibrations or safety hazards caused by chopped, angled, and welded radius arms.

Tractech Truetrac Rear Differential (912A383) $620

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The rear Truetrac operates in an identical fashion to the front version and provides more traction than any open differential, as well as providing additional strength. The rear Truetrac will not provide as much traction as a true locking rear differential, but much more than most people believe. The rear Truetrac is an excellent choice for those that want more traction than an open differential will provide but who are reluctant for whatever reason to fit a rear locking differential. This is a drop-in replacement for the rear differentials on all Discovery Series I's and II's, Range Rover Classics from 1994 to 1995, and all Defender 90's.

Tractech Detroit Locker (187SL-173A) $675

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Bearings are included in the above price

This locking differential is the toughest locking differential currently available for your Land Rover. The Detroit will not permit a wheel to turn more slowly than the ring gear. If your center differential is locked and you're giving the engine gas, then both of the rear wheels will turn at least as fast as the ring gear is turning. On the road, the Detroit automatically senses differentiation and unlocks in turns by letting the outside wheel turn faster than the ring gear and the inside wheel. The Model 187SL-173A replaces the weak factory rear differential and carrier on all Discovery Series I's, Range Rover Classics from 1994 to 1995, and all Defender 90's. For earlier vehicles equipped with 10-spline halfshafts, we highly recommend upgrading to 24-spline halfshafts for added durability. Detroit Lockers are suitable for use only in the rear axles on full-time 4WD Land Rovers.

 

With its open carrier and two-pinion design, the stock differential is weak in addition to giving poor traction on uneven or slippery surfaces.

Another standard differential breaks from wear and tear. Note that the pin that holds the two pinion gears is broken and one end of the pin protrudes from the carrier. Unfortunately, this is all to common on the stock differentials. The harder the trail, the more spinning and bouncing one must necessarily do to overcome obstacles because of the low traction provided by open differentials. This puts a tremendous amount of strain on all parts of the vehicle, but especially the differential. If one wheel is spinning and suddenly receives traction, the torque is violently sent to the opposing wheel on the axle. This is the result.

This is a different differential from the one pictured above. The cross pin on this unit appears intact, but the side gears are mangled from heavy use.

Like most broken differentials, this second unit broke during a trip and had to be replaced in the field. Luckily, the owners and their trail mates had the proper tools on hand and a Power Tank to power their air tools to facilitate the installation of a replacement differential.

In addition to being burdened with a weak pin, the factory differential is also plagued with a weak carrier. The carrier is cut out on both sides to permit easy installation of the spider gears and the side gears. However, the holes substantially weaken the carrier and permit breakage under hard use.

With its solid carrier, the Detroit Locker is approximately twice as strong as the factory differential. The Detroit Locker is strong enough that some other component in the driveline will most almost certainly break before the Detroit Locker will.

Here is a Detroit Locker without the Timken bearings pressed onto the carrier. We recommend the fitment of new carrier bearings for all replacement differentials as the factory differential bearings are usually not concentric. Furthermore, removal of the carrier bearings is time-consuming and may damage the bearings. We believe that it is far better to press on new carrier bearings with every replacement. Cost of the pressed-on bearings is only $50 per differential.

Here the carrier bearings are pressed onto the Detroit Locker's carrier. The bearings' races are not pictured here, but are included with every differential.

The Detroit Locker is a drop-in replacement for the factory differential. The 10 holes for the ring gear exactly match those of the factory differential (Detroit Locker on the left, standard differential on the right). No modification to either the Detroit Locker, the ring gear, or the axle's third member is required for a proper installation of the Detroit Locker.

Here are some cutaway models of the Detroit Locker from the 2001 SEMA Show. Note that all Detroit Lockers come equipped with two cross pins rather than one, as well as solid carriers. These features make the Detroit substantially stronger than the factory differential.

How does the Detroit Locker operate? These photos from the 2002 SEMA Show demonstrate how. The standard running mode for the Detroit Locker is to operate in a locked condition, shown in the left photo. The Detroit Locker then unlocks when differentiation is required, such as when the vehicle is turning. When differentiation is required, the the two dog clutches on either side of the spider assembly spread apart and permit the unit to unlock, as shown in the right photo.

One can simulate this unlocking on Tractech's demonstration model by turning one wheel one way and the other wheel the other way. In such case, the dog clutches separate and the unit unlocks. When both wheels are turned in the same direction, the unit remains rigidly locked. The Detroit Locker works in both forward and reverse.

Unlike with some other locking differentials, the Detroit Locker is completely self-contained and requires no wires, Power Tank, cables, or air hoses to operate like the ARB Air Locker. Accordingly, the Detroit Locker is extremely reliable. The Detroit Locker also does not require special lubricants or friction modifiers. Just pour 90wt gear oil into your axle and you are ready to roll. The Detroit Locker requires no more maintenance than your factory differential.

Unlike the Detroit Locker, the Truetrac is a limited-slip differential and is suitable for both front and rear applications. Like the Detroit Locker, the Truetrac is equipped with a solid differential carrier for maximum strength. A Truetrac is approximately twice as strong as the factory differential.

Unlike the Truetrac, most limited-slip differentials like the one shown above operate like open differentials but have spring-loaded clutch packs to mitigate the otherwise unrestricted slip between the two sides of the differential. This is a far inferior design to that of the Truetrac. These clutch packs wear out and the differential becomes more and more like an open differential with use. Also, these differentials create handling problems on high-traction surfaces like the road because they want to remain tight and prevent differentiation between the two wheels. Finally, these clutch-driven limited slips require special friction modifiers to be mixed into the gear oil to permit the clutch packs to operate smoothly.

The Truetrac is gear-driven, just like the standard differential, and operates on a completely different principle. The Truetrac operates like an open differential in high-traction conditions. On low-traction surfaces, the helical side gears prevent one side from spinning out of control while the other side remains stationary, as often occurs with an open differential. During times of severe differentiation when one side of the axle wants to spin out of control, the helical worm gears are pushed away from the larger helical gears and pushed into the carrier. The additional resistance on the side with less traction diverts torque to the other side of the axle. The gear-driven operation provides several dramatic advantages over the clutch-operated designs. There are no clutch packs to wear out on the Truetrac, and a Truetrac wears no faster than any standard differential. The operation of the Truetrac is also smoother and more transparent than the clutch-operated designs. Finally, there is no special friction modifier required for proper use, and standard 90wt gear oil is the fluid of choice with the Truetrac.

Like the Detroit Locker, the Truetrac is a true drop-in replacement for the factory differential. No modification of the Truetrac, ring gear, or third member is required for a proper installation of the Truetrac. No special lubricants are required. Just drop in the Truetrac and drive.

Many people who have lifted their vehicles find that their vehicles have lost the straight-line tracking ability that the factory height provided. This is caused primarily by the loss of caster angle in the front axle caused by the lift. It is currently fashionable to correct the caster angle by fitting "caster-corrected" radius arms. It is our considered opinion that these radius arms are not a proper solution for the caster problem, for many reasons. First, these arms are invariably chopped and welded, which many do not consider to be safe. The radius arms take a tremendous amount of stress during braking, and Land Rover made the radius arms in a one-piece forging for a good reason. Second, these bent radius arms point the front pinion downward, causing driveline vibrations with a double-carden front driveshaft, which likes to have zero or very close to zero degrees of angle in the pinion end. Third, the bent radius arms still leave a weak front differential that provides little traction. In our opinion, fitting a front Truetrac differential will solve the caster problem more effectively. The Truetrac makes the vehicle want to steer very straight and compensates for the loss of caster in lifted vehicles. By solving the caster problem with the Truetrac, the radius arms are left as one-piece forgings the way Land Rover intended and are not weakened in any fashion. Also, the weak and low-traction front differential is replaced with a strong and high-traction Truetrac. We believe the Truetrac is currently the best and most elegant solution for the caster problem, as well as for simply obtaining more traction in the front axle.

Even if your vehicle is fitted with Electronic Traction Control like this Disco2, you will find a Truetrac greatly prevents wheelspin and the shifting of the vehicle that results when spinning wheels suddenly gain traction.

As with the Detroit, we highly recommend the fitment of new Timken bearings rather than pulling the worn and uneven factory bearings from your open differential and putting them on your new Truetrac. The minimal cost of new bearings is cheap insurance.