A6 rear differential fluid change

Kunz, Bob bob.kunz at hp.com
Wed Apr 15 10:48:24 PDT 2009

Need your collective wisdom, BTDT type of stuff.

Patient is a '99 A6 Avant new to the household (120K miles). Wanted to change out or at least check level of the rear fluid but the fill plug is really solidly stuck in there. I tried perhaps 200 ft-lbs of torque with simple ratchets and no movement. Soaking in liquid wrench for a few hours and still no movement.

I was going to take the brute force method and apply an impact wrench to it but then thought that might crack the case and I certainly don't want to do that. Any other thoughts to get the fill plug out? Or have others applied an impact wrench with success?


'86 5Ks Avant
'99 A6 Avant
'02 TTQR
'07 Q7 4.2P

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