Differentials - Questions & Answers

1. I've heard that the spider gears are weak in BMW differentials.
In a non-limited slip differential, the spider gears can break easily if one wheel spins hard on a slick surface. Because this can't happen in a limited slip, spider gear failures are extremely rare.

2. Is there any drawback to a limited slip?
If you accelerate too quickly during inclement weather and loose traction, both tires could break loose at once causing the rear end to swing out. By going easy on the gas pedal, when roads are wet and icy, you'll notice an improvement in traction over conventional rear ends.

3. Increasing lock up and fixing leaky seals.
I purchased a BMW factory limited slip. I'd like to increase the lock up and at the same time get the leaky seals in my rear fixed. Does this present a problem? See answer to #4.

4. Adding a "Maximum Stick" and fixing leaky seals
like to add a "Maximum Stick" (limited slip unit) and at the same time get the leaky seals in my rear fixed. Does this present a problem?
After 100,000 miles the most frequent complaint is one of leakage, which is better off left alone unless you intend to completely rebuild. For instance, if you remove the nut and flange to replace a leaking front seal, there is no possible way to tighten the flange nut sufficiently without overloading the pinion shaft bearings. There is a 'crush-collar' between the two tapered roller bearings on the pinion shaft that allows the nut to be tightened (over 200 ft. lbs.) without applying this force to the bearings themselves. Setting the clearance for the pinion bearings and adjusting the ring gear pinion backlash are, at times, somewhat exacting tasks and are therefore risky enough to discourage most mechanics from rebuilding.

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