Limited Slip Differential

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Limited Slip Differentials are referred to as a Slipper or as an LSD. This contrasts to the normal differential fitted that is known as an Open Diff.

LSDs were fitted as standard to the 325i Sport and M3. They were not standard on the 318iS, but were on option available to all E30 models.

Case sizes

E30s had two differential case sizes, which are interchangeable and the same width but will require adjustment of the propshaft. Learn more about fitting a differential.

E30s used either a Small Case or Medium Case differential. Other models used a Large Case which is not directly interchangeable but the internals can be swapped.

Ratios

Below is a list of ratio and cars in which they can be found.

  • 3.15 - M3
  • 3.64 - prefacelft 325i
  • 3.73 - facelift 325i
  • 3.91 - facelift 325i touring, cabrio, 325i with getrag 260 sport
  • 4.10 - found optionally on UK spec 318i/318iS 2/4dr in Small Case, and on all US M3 models in Medium Case.
  • 4.27 -
  • 4.44 -

For more info on these numbers, learn more about differentials.

Identification

To identify an LSD one can first check for the presence of the tag on the rear casing. The ratio on this will be prefixed with an S for LSDs.

Alternatively one can jack up one rear wheel, ensure the car is out of gear and hand-brake is off then turn the raised wheel. Resistance on that wheel would usually indicate an LSD. An alternative method is to try to leave skid-marks pulling away on good tarmac, two tyre marks for more than a few inches would indicate a properly "locking" LSD. This won't work so well on grass or gravel as on loose surfaces both wheels can slip easier even for non-limited slip differential types.

Oil

E30 LSDs are clutch plate type and require special oil. The BMW recommended oil is Castrol SAF-XJ