Rear Differential Fluid change how-to for the E9X M3s. Do all work at your own risk – this, as most trans & gear oil changes are, is a pretty straightforward flush. Probably the easiest of the maint jobs you can do on your M3.

Requires:

• Jack/stands/ramp
• 14mm hex head
• Drain pan
• Fluid pump (I use this)
• 2 quarts of GL5 75w140 (I used Red Line 75w110, 1.25 qts used)

I’m not a huge fan of using very thick fluids, and I think the 75w110 is a nice middle ground for me. I don’t know what’s special about this rear diff but the car doesn’t make that much power/torque, so I’m not sure why 75w140 is called for. Anyway, go with what you are comfortable with, as that is the most important thing. 75w110 was good enough for Bimmerworld’s track car, so it’s good enough for me.

Car up on my Quick Jack. Both the drain & fill plugs are on the passenger’s side of the car, right next to each other.

Loosen fill, crank open the drain:

Close the drain and pump in new fluid. Torque specs for fill and drain are roughly 45 lbft, I just do a little more hand tight here.

Once fluid starts coming out of the fill hole, you’re set. Always make sure to verify that the fluid amount you’ve used is roughly correct – should be about 1.25 quarts used here. Close it up and you’re all set. One thing to note, that is a massive cooler on the rear diff.