Hey guys im new here. I have an 88 f250 with a five speed and i was wondering if someone could tell me what type of oil to use in the differentials and my transfer case. Also if i take off the diff cover do i need a new gasket or can i use some rtv sealant.

 

For the axles you need something like 85w90 gear oil. If the rear diff is limited slip you will also need some friction modifier.
The transfer case needs auto trans fluid (same fluid as the trans).
Should be alright with RTV on the cover if you give it time to set after cleaning the surfaces well.

 

Thanks. I really appreciate the fast response.