85 or c4 differential fluid
Team Owner
Joined: Dec 1999
Posts: 34,873
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From: Lacey WA RVN 68-69
NCM Sinkhole Donor
The Owner's Manual doesn't have a real recommendation, but you can't hurt anything by doing it every 50K miles if the car sees general street use.
A good brand of a GL-5 rated 80W-90 gear oil and a bottle of the GM positraction additive will work fine.
A good brand of a GL-5 rated 80W-90 gear oil and a bottle of the GM positraction additive will work fine.
