So I just changed my rear diff fluid for the first time since buying my '08 535xi last month. The car has 69k miles on it and I'm not sure it was ever changed. The fluid I suctioned out came out to about 2/3 litre. I pumped the new fluid in until it started overflowing, which amounted to about 1 1/3 litre--roughly double. Did I overfill?


BTW, the moaning/humming noise that was there before the refill when stepping on/off the gas at highway speeds is quieter, but not completely gone. Do I need a new diff?

 

If the car was level when the differential was refilled, then the fluid level is correct when fluid reaches edge of hole.
N54 automatic. 1.0 ltrs (1.05 qts)
N54 manual 1.2 ltrs (1.27 qts)

 

Thanks, jtb. It was mostly level, although I had the a**-end jacked up in my driveway so I could do the work; maybe 5" above resting level? That may explain why I was able to get 1.25 - 1.3L in there! Doubt it'll cause any issues, but next time I get to a level lift, I'll open the plug and let any excess drain.

 

If it's an automatic, believe I would correct it. Overfilling can be just as bad as underfilling...

 

Sounds good. It is an automatic, but...is the rear diff different on a manual vs automatic AWD?

 

Bentley doesn't differentiate between AWD and RWD on the differential, only between Manuel and Automatic That is where the fluid fills for the N54 came from.