Defender ATB Limited Slip Differential Lock

The Defender Limited Slip Differential - ATB Automatic Torque Biasing - Limited slip differential.

The Land Rover Defender Limited Slip Differential ATB is a so-called "Helical Gear" differential - with six gear pockets. It increases the off-road capability of the Defender many times over. There are a number of other Limited Slip differentials available for the Land Rover Defender, Discovery 1 or Range Rover Classic. Such as the Limited Slip with a friction disc clutch and the TYPE T1 Torsen.
The Torsen T1 was the predecessor of today's ATB differentials.

Friction disc LSD differential - obsolete technically with high wear and tear

An ATB differential is technically and from the durability clearly superior to the friction disc variant. Especially at very high loads under adverse conditions and the associated wear, which acts perpetually on the organic friction discs. With the friction disc differential, high friction is required to reduce slip on the drive wheels. This high preload results in harsh vibration effects and causes high premature wear.

The Torsen T1 differential was based on a mechanical principle. To produce transverse torque, effectively coupled worm and gear wheels are driven backwards to produce the required frictional loads. These often failed under this high load, and the worm gears were destroyed after not too long of use.

The ATB differential (Automatic Torque Baisin) is the helical type and has many advantages. ATB differentials are practically imperceptible to the driver during normal road driving, since the friction between the gear and guide does not intervene.

Disadvantage and explanation of handling in off-road use

One disadvantage of the ATB Limited Slip Differential is that one wheel per axle must always be loaded to be effective. If there is no load situation, for example a drive axle, the wheel with traction would be loaded about three times as much as the wheel without traction. This means that there is no 100% propulsion here. To overcome this problem, the Defender Limited Slip Differential, is equipped with some preload springs, and the trick is to lightly apply the brake with your left foot while giving it some throttle. This maneuver fools the differential by distributing a load to the slip side. On the Land Rover Defender ATB differential, the load distribution is about 3: 1, which is multiplied to the other side. The loss of drive, therefore, attributed to the trick with the brake, thus distributes the power evenly to both wheels. In a vehicle with automatic traction control, this braking is automatically simulated by the ABS Modulator. The ATB differential provides additional traction by multiplication on Defender models with Traction Control (TC).

Mounting and accessories for Land Rover Defender and Discovery 1 models

The Land Rover ATB differential can be mounted at the front or rear. On the front axle, the Defender's tracking through the steering will be slightly higher compared to the standard differential. You will notice this stiffer steering very little when cornering.

So why use an ATB instead of a 100% differential lock? When riding on a low traction surface, such as, sand, snow or wet grass, you could cause some loss of traction when cornering with a 100% differential lock. This is because both wheels are driven at the same speed. The ATB lock allows the difference in wheel speed to be equalized even on loose surfaces, but at the same time tries to equalize the torque at each wheel. This reduces the possibility of a so-called spin-out situation.

When mounting for Defender 110 and 130 rear axle, an adapter kit is still needed. For Defender 90, Discovery 1 and Range Rover Classic the differentials for front & rear axle are the same.

Safety Note: Due to the nature of the ATB differential, we do not recommend vehicle with lock on a roller brake tester.

Mounting Note: When mounting for Defender 110 and 130 rear axle, an adapter kit is still needed. For Defender 90, Discovery 1 and Range Rover Classic the differentials for front & rear axle are the same.