The Quaife ATB (Automatic Torque Biasing) differential is a unique type of limited-slip diff that substantially improves traction for powerful vehicles using only gear mechanisms. This clever design revolutionised the differential market - offering a superior level of performance and warranties compared to its competitors.

We offer two methods of upgrading your E36 M3 3.0L or 3.2L - we can supply you with the Quaife ATB Limited Slip Differential Kit (including new side bearings for 3.2L cars) for you to have the retrofit performed by a specialist yourself or you can send us your differential for an in house conversion to be performed.

The Quaife ATB Limited Slip Differential Kit comes with everything you need to retrofit your existing 'clutch' LSD with the Quaife ATB unit. The work is highly recommended to be performed by a differential specialist. The E36 M3 3.2L also requires new side bearings which are supplied in the kit.

We offer an in house retrofit service where you can send your differential to us to have the conversion carried out. Depending on your location, the process can take 5-15 days including freight transit time. The cost is also fully inclusive of freight to bring your standard differential to us and the return. All you need to do is organise the removal of your differential (at your own cost) and we can take care of the rest.

All standard BMW models come from the factory fitted with the basic "open differential" - a simple device that allows the driving wheels to turn at different speeds (enabling the car to navigate around corners). The problem with the open diff is that it can only ever apply the same amount of torque to both driving wheels, so when a wheel slips, it will only put through the amount of torque it requires to power that spinning wheel (very little!). The car spins away power in these instances.

Additionally, BMW use various electronic traction systems that "curb" power to the drive wheels during traction loss (indicated by the flashing traction light on your dashboard). The Dynamic Stability Control system (DSC) is designed to "curb the engine output and stop slip on the wheels", a good feature in theory, but is still in its early stages of development and is way too intrusive, often frustrating the driver when trying to push on. If you accelerate hard from slow speeds, or try to power out of turns (especially in slippery conditions), the loss of traction will make the engine sap power away from the wheels. Turbocharged rear-wheel drive cars with high torque outputs suffer the most, such as BMW's M135i, and conditions are worsened by the fact they are equipped with run-flat tyres and stiff suspensions. Of course if you are lucky enough to have sufficiently deep pockets, all BMW M-Powers come from the factory with a mechanical limited-slip differential, demonstrating that even BMW themselves know that powerful cars need these important devices.

Fortunately, there are clever differentials out there on the aftermarket that will transfer torque to the wheel with more traction rather than take it away... 

The Quaife unit uses sets of floating helical cut gear pinions that run in pockets and mesh during normal driving, acting as an open diff. Should one of the driving wheels start to spin however, the helical gears start to generate a torque bias thanks to the axial and radial thrust of the helical gear pinions in their pockets. The result is an instantaneous and progressive transfer of torque away from the spinning wheel to the one with more traction, always varying accordingly and automatically.

With the DSC and traction systems switched off during traction loss, you will feel the Quaife transferring the power to the wheel with more grip in a smooth and predictable manner. Any movement at the rear end is controlled and intuitive for the driver. With the traction systems switched on, you will rarely ever see the light flicker on your dashboard as the Quaife allows you to power through any loss of traction, working in perfect harmony with all of the BMW's standard equipment.

The car ultimately becomes easier to control and is able to apply its power to the tarmac with maximum effect. Acceleration, cornering speeds, handling, steering, and overall dynamics of the car are dramatically improved! The Quaife is capable of varying the torque split from 0-80%, and does this quietly and smoothly in operation. It does not affect any of the traction systems on the car, and does not affect the manufacturer's warranty. All backed by its own worldwide lifetime guarantee.

Watch BBC Top Gear's Chris Harris demonstrate the Quaife ATB in our 335i during his Autocar days.