Hey everyone.
I just got done putting 4.10 Richmonds in my '94 and I thought I'd see if anyone had anything to say about the gear oil. The car had Redline in it when I bought it. I'm assuming it was the factory recommended 85w90. However, the Richmond oil was 75w140. It was also GL-6 rated and I can't find any brand that makes that besides them.
Here's the question. From what I've read it seems that Royal Purple is the best choice in any regard. I'm asking for any and all opinions from the F-body community on brand choice (Redline, Richmond, or Royal Purple), and whether to stay with factory 85w90 or the Richmond choice of 75w140 or something else.
The car is primarily a daily driver although it is quite modified. I also run about 15-20 passes a month in this car. Thanks to anyone for any opinion on your experience or things you've read or heard.

Michael

 

The guy who installed my gears used Coastal 85w90...and he said to stay away from synthetic during break-in period, and that he wouldn't even bother with synthetic at all. My gears don't whine at all, and so far I have about 10 launches on BFG's, still no problems (Strange 3.73s). Just don't forget the GM limited slip additive.

 

GM

 

IMO, any non synthetic gear oils are pretty much the same. If your going synthetic, stick with either Royal Purple or redline. I use Royal purple in mine.

 

I thought the factory weight was 80w90? I use Spirax fluid with no problems.

 

ttt