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      11-03-2013, 06:43 PM   #154
Brigadier General
SenorFunkyPants's Avatar
United Kingdom

Drives: 2017 M4 CP DCT
Join Date: Mar 2009
Location: UK

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Could it be a stone caught up in the rear disk brake rain shield?
Typical diff clutch pack noise is more of a rubbing groaning noise than a metallic pinging.
The oem fill for the diff is castrol SAF-XJ which already contains friction modifiers (not to be confused with the BMW customised version with even more friction modifiers). I sometime wonder if the noisy diffs are caused by dealers replacing the SAF-XJ diff oil with some other less suitable alternative LSD oil.