12 bolt diff fluid

[hrlyfxdl]

Hey, I tried searching the strings on here and couldn't find this posted before. I am replacing the gasket and cover on my 68 Camaro, and wondering what people recommend for the replacement fluid? It's a 12 bolt posi rearend. It's not stock, it's a 3.73 in there, supposed to be a 3.31. I have some Royal Purple 75w90, and states it doesn't damage any yellow metal parts. Anyway, what would you recommend as a new fluid with todays technology in fluids, and how full? Thanks.

[ko-lek-tor]

http://www.camaros.org/forum/index.php?topic=566.msg3107#msg3107

Royal Purple eh? Sounds like they are trying to re-invent the wheel? If it smells bad, it is good to use. Why, because that is sulfur added to provide lube. I don't recommend synthetics. all oils have a SAE rating somewhere on the package. I am sure that stuff you have will work ok. You will need an additive for the posi clutch packs to prevent chatter. Used to be Sperm Whale oil. I am sure it is something else. Used to get it at the dealer, back when this country was...ah, don't go there Bent. I'm sure you can find it at a well known chain auto store.

[Mike S]

 I was faced with the same decisions when I refilled my 12 bolt posi. I went with AC Delco GL4 fluid (I think it was 75W90) and AC Delco 10-4003 posi additive.

Mike

[hrlyfxdl]

Thanks guys, appreciate the input. I went and got some fluid last night based on the postings and prior string. Much appreciated. I dare say, this is one of the few GOOD places on the internet.