[sunealio]

After dropping my Z4M off at a friend's shop to swap diffs last week, both rear axles are leaking massive amounts of grease near the wheelhub, in the area circled in the attached picture. I am beyond confused as to why both are leaking immediately following the install--and not because of torn CV boots?

Installer lowered the entire subframe inc. trailing arms to swap the diff (which I didn't think was necessary). I believe he also pulled the axles out of the hubs in the process.

Additionally, I purchased a "low-mile" used diff from a dismantler, which was silent for the first 300mi, but now clunks off the line. The noise can be replicated with the car on the lift by quickly moving the wheels from a stop and seems to come from inside of the diff. Mounts were replaced with AKG black bushings.

- What would cause the axles to leak out of here?
- Do I need to replace them now?
- Was my used diff dead on arrival, or will more friction modifier solve my clunk?

Grabbing photos on the lift later. All thoughts are appreciated.