October 24, 2006:

Limited Slip Differential

An interesting response to NAM member DarkMiniCooperS from GNK, who created the LSD in our GPs:
Thanks for your recent enquiry on GKN’s website and nice to hear good things about our ‘SuperLSD’.
The design life for the differential is equal to that of the vehicle – call it 150,000 miles – but that depends on usage and maintenance. The main wear related effects will be a gradual drop-off in torque biasing capability (called ‘TBR’) and an inevitable increase in the propensity to make noise when working hard. These two aspects are common for all torque biasing LSDs irrespective of the mechanical layout of the LSD or it’s manufacturer.
The TBR of the SuperLSD that you have fitted into your Mini is in the range 1.8 to 2. As you say it is noticeable enough to be useful, but does not introduce the issues related to high TBR devices in front wheel drive vehicles. I tested two Mini’s back to back on a frozen Swedish lake a couple of years ago and the LSD equipped vehicle had better traction (obviously), but more importantly was much more settled backing off the throttle into bends. It was easier to drive quickly that the open differential car.
Since it sounds like you are an enthusiast you need to pay attention to maintenance. I would recommend that you keep a close eye on the level and condition of your transmission fluid. Always use the BMW recommended fluid, since it was developed for this application. An expensive aftermarket fluid might work just as well, but it may also have dire consequences for your seals, bearings, gears or the LSD. It may also affect your shift quality. Be vigilant for noise during split mu launches or repetitive hard cornering. The differential is not being damaged, but the fluid is being overworked and overheated and hence the potential need to renew it.

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