BMW E46 M3 DIY: Differential Fluid


Easy (1-1.5hrs)


  • Jack and Stands or ramps
  • 12 & 14mm hex sockets
  • Extension Set (3″ & 6″)
  • Ratchet wrench
  • Torque wrench
  • Drain pan 1 gallon capacity
  • Fluid pump
  • Gloves


Prior to changing out the differential fluid, drive the car around for 5 minutes to warm up the differential fluid in order to make the flush process faster and more thorough. If your differential is making a whining noise louder than usual, it’s a good idea to change out the fluid if you haven’t done so. BMW fluid originally started out as 75w-90, but it was superseded by 75w-140. Make sure it’s friction modified or designed for limited slip applications if you are straying away from the OE fluid.

Step 1 – Raise the car

The best way to raise the car for this job is to raise it evenly, or as long as it doesn’t have too much of a front rake. This allows most of the old fluid to drain out. Raise the car so you have enough access to the rear drain and fill bolts.

Step 2 – Loosen the fill bolt

First unbolt the fill bolt, which is the hex bolt on top. Due to mid-production changes, this bolt is either a 12mm or 14mm hex bolt. It helps to have a breaker bar or longer ratchet to break it loose. Have your drain pan underneath, as some excess fluid may drip out at this time. The fluid may still be hot, so be careful or wait a few extra minutes.

Step 3 – Loosen the drain bolt

Next unbolt the bottom bolt, which is the drain bolt. This is a 14mm hex bolt. The majority of the old fluid will drain during this step and may take up to 30 minutes.

Step 4 – Replace and install drain bolt

To make things a little more complicated, there are two types of drain/fill bolt. One with a built in green washer, and one that uses the external crush washer. Install the drain bolt with the washer and torque to the following:

  • With green 0-ring: 44 ft-lbs
  • Without o-ring: 48 ft-lbs

Step 5 – Filling fresh fluid

Using the pump, insert the tube into the fill hole and pump away until it start overflowing. It’s a good idea to keep the fill bolt/washer ready once the fresh fluid start seeping out the fill hole so you can cap it off quickly. Same torque specs apply as the drain bolt.

  • With green 0-ring: 44 ft-lbs
  • Without o-ring: 48 ft-lbs

Step 6 – Clean up and break-in

Wipe down any excess fluid and drive around in an empty lot doing figure eight circles. Check for leaks.