First off, I know the answers probably already been answered but I can't find it. Sorry in advance. I need to change the front and rear diff fluid and I just want to make sure Im using the right fluid. Im driving a 94 4x4 with 135k miles. Just bought it so not sure when last service was, if ever. I picked up some valvoline 80w90 with limited slip additive for the front. I didnt realize that it had the LS add until I got home. Is that ok to use in the front. and then what to use in the rear? I am using a syn atf for the trans case as well. I have seen discussions about this, but it seems to all be for 99 and newer. Just making sure im putting the right stuff in. Thanks for the help!

 

Anyone? My manual says nothing about what gear oil to use.

 

80w90 is fine for both front and rear. Putting limited slip additive gear oil in a Non LS diff won't hurt it.

Right out of the haynes Manual:

Front- SAE 80w-90 gear lube. (with LS additive if you have a locker)
Back- API GL-5 SAE 90 Hypoid gear lube

 

thanks a lot. I havent had time to go pick up a manual, so thanks for the info!

 

mine also takes 80w90 but I talked to a ford tech and he said I could use 75w140 synthlic

 

thats in an 03 though right? This is why I was getting confused. some people say 90, 75w140, 80w90. there should be a sticky by year or gen on what to use.

 

after reading the back of the bottle online I'M going to get 75w90!it has what 80w90 has so now it settled 75w90 it is and it's a little cheaper then 140.