Mini Cooper - Transmission & Differential

Equalizing Your Output

The final station before power is applied to the axles is the differential. Mini offers only one differential in the Cooper. This stock differential is an open type, which provides power to both right and left front wheels. As with all other open differentials, the power goes to the wheel that slips or spins.  Our Grand-Am racing experience taught us that in corner exits, whether fast or slow corners, the inside wheel always wants to get there first, usually going up in smoke while trying. This makes for a great show for the fans, but it also results in slower lap times since the slipping wheel is not applying the power needed for acceleration. With the 200 horsepower Mini engine, the front tires easily break loose.  That might be okay off the line on a quick start, but it is not the fastest way around a corner.

We offer two solutions to the stock differential.  The first solution is
Formula One technology: the Torsen Differential, or more commonly referred to by the manufacturer Quaiffe.  These units are made in the U.K., and we maintain a stock for ready access.  The cost for this torque-sensing unit is $1200 and requires the removal of the engine and gearbox.  Labor is $900 for removing the engine and gearbox, which is same operation for the clutch/flywheel upgrade.  Schedule the differential and clutch upgrades for the same visit and labor is $900 TOTAL for both, saving you $900 if the upgrades were performed separately.  Labor to disassemble the gearbox and install the differential is an additional $500.  Total installation price of the Quaiffe is $2600.

Another cost-effective alternative toward a limited slip type of differential is from Phantom Grip in Florida.  These innovative folks devised a method to modify the existing stock differential for a significant savings over the torque sensing type differential.  We helped develop versions of their invention for race duty in our Grand-Am ST I Minis.  The device can be installed in the stock Mini differential for $800 including parts and labor, resulting in a total installed price of $1700.  We used the modified differential all racing season with no failures, and found it to
be comparable to the Quaiffe.  

One Mini had the Phantom Grip device and the other Mini on the team used the Quaiffe torque-sensing differential.  Each unit performed well with no clear winner in lap times or driver preference. The choice is yours as to which unit will suit you and your pocketbook best. Regardless of which option you choose, you will enjoy the increased traction and stability offered by either.