Im going to be having my 10-bolt rear end rebuilt with bigger gears as well as installing an eaton posi. What I want to know is what is the best brand of oil I can use to break in my rear end after I have it rebuilt and about how much do I need . I have never done this rebuild before and the shop that is doing it wants me to supply all parts and fuilds needed . Any help would be awsome.
Thanks

I Would run the Royal Purple Max Gear oil. Never had any problems using Royal purple in any of my vehicles.

thanks for the input about how much will i need

does any body know exactly how much oil i should use and is there a specfic weight of oil for my differentail, i dont want to put all the new parts in then add the wrong fluid and blow a seal or something. Plus i have heard of guys using additives , Will i need any?

personally i'd run 75w90 mobil 1 synthetic ,but any 75w90 gear oil will do the trick.

as for additives i'm not sure if yours requires one ,but i know for a fact mobile 1 has the posi additive already in it, as well as lucas brand gear oil does too (work at a parts store).

Personally i bought mobile 1 and cheap parts store posi additive for my old go lock and it works great for having 210k miles on it.

I have an eaton posi and I had problems with it ractheting. I called Eaton and they told me NEVER to run a synthetic gear oil with the Eaton unit. They said a standard high quality 75-90 weight with the GM posi additive is preferred. You can run other posi additive they said, but it's not as effective as the GM stuff.

thanks for the info

https://www.thirdgen.org/forums/tran...-10-bolts.html

JamesC