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Differential Trouble After Service
I purchased a 2007 E60 manual with about 90k miles a few weeks ago. On the test drives, everything ran flawlessly (total 30-40 miles of mixed driving). I did a PPI at an independent BMW specialist and the mechanic and I noticed the rear diff was leaking and I agreed he should replace the seals and flush with new fluid, which he did, using the SAF-XJ + FM booster.
Prior to the new fluid and seal replacement, the diff did not make any noise, but now it makes a telltale grinding sound reasonably frequently on slow turns at/near full lock. The mechanic advised me to do three slow circles in either direction, which I did to no avail. So a few days later I did 15-20 in each direction, which seemed to correct it for the rest of the drive, but it has since returned.
Having read some threads about this problem on here, I know the BMW TSB says it takes up to 600 miles for noise to go away, but my concern is that there was no noise before they worked on the diff and now there is. Plus lots of folks seem to report a previously noisy diff being fixed immediately when they changed fluid, let alone a diff that showed no issues.
Is it safe to drive on a noisy diff for 600 miles, waiting for the sound to go away? Should I have the shop redo the fluid change?
Thanks for any help or advice!