I changed my diff fluid and I never smelled such foul odors. Do not spill it in the garage! 100,000 miles and 15 years old? Who knows. The Prev owner had no records and I don't know if it was ever done.

I wondered if it is done on the flat floor. I jacked up the rear and filled the diff then set it down, let it drip and then jacked it back up and put in the plug. I think that works. I used regular gear oil but added some additive for the limited slip diff.

Seems to be great 15,000 miles later with no noises or anything.

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Steve
1985 Mercedes 500SL Euro (Gray market)
1995 BMW 520i Euro (Gray market)
1992 BMW 525it Wagon
1994 Honda Del Sol Si