Drain & Refill
- Park the car on a level surface and set the parking brake.
- Remove the filler plug.
- Place a large container underneath the rear axle. Remove the drain plug at the bottom of the differential and allow all lubricant to drain into the pan.
- When all lubricant has drained out, clean and replace the drain plug. Use a new crush washer. Torque to 40 ft. lbs. (55 Nm) on the rear axle and 14 ft. lbs. (20 Nm) on the front axle.
- On E30 models, refill with GL-5 hypoid-type gear oil, SAE 90, On E36 models refill with the recommended lubricant until it runs out of the fill hole. Replace the filler plug and torque to 40 ft. lbs. (55 Nm). Run the car and check for leaks.
Fluid Level Check
- With the car on a level surface, remove the filler plug from the side of the differential.
- If the oil begins to trickle out of the hole, there is enough. Otherwise, carefully insert your finger (watch out for sharp threads) into the hole and check that the oil is up to the bottom edge of the filler hole.
- If the fluid level is low, add oil through the hole until the level is at the edge of the hole. Most gear oils come in a plastic squeeze bottle with a nozzle; making additions is simple. You can also use a common kitchen baster. On E30 models use only standard GL-5 hypoid-type gear oil, SAE 90. On E36 models use the recommended lubricant.
Prior to the introduction of the E36 models, most differentials used GL-5 hypoid-type gear oil, SAE 90.
With the introduction of the E36 models, the fluid recommendations for the differential varies from model to model and the type of differential that is installed, (Limited Slip or not). BMW released a Service Information Bulletin S. I. 33 01 92 (3667) dated May 1996 to inform the dealer network that a synthetic based lubricant is now being installed as a factory fill.
The highlights of the bulletin are as follows:
BMW Synthetic Final Drive Oil SAF-XO : For vehicles without a multi-plate limited slip differential, or with a viscous-type differential lock (325iX/iXA)
BMW Synthetic Final Drive Oil SAF-XLS : For vehicles with a multi-plate limited slip differential. DO NOT use in the Z3 Roadster
BMW Synthetic Final Drive Oil SAF-XJ : For Z3 Roadsters with a multi-plate limited slip differential.