I have 2.56 gears in my differential and I'm pretty sure that the fluid hasn't been changed in its lifetime. I am looking to change it out with Royal Purple or AMSOil and was wondering what weight of oil to use.

 

Hey. 75w90 or 80w90 should workfine for an open or posi diff. Iusually go to this site for any specific questions, since I bought my posi unitthere..
http://www.auburngear.com/aftermarke...6pagesize%3d20

 

Cool, thanks man. I notice in the manuals on these that they're talking about a "non-synthetic". Do you think it's just because they're installing a set of new gears that need to go through a break-in or is there another reason that you know of?

 

Im not sure why the say not to usesynthetic, but that is my guess why, too.I did talk to them on the phone about the additive, but I dont remember the subject of synthetic in the conversation, it may be that the additive doesnt play well with synthetic. Maybe someone else knows??