I have an 01 xj i want to change the rear diff fluid i think its the chrysler 8.25 rear and i wanted to know If i should use 75 or 80w90 gl5 and is the front diff the same? And is it better to use RTV high temp copper on the cover or a felpro gasket.Also im going to change the T case fluid while im at it so is dexron III ATF the correct fluid its a 231 transfer case. Any tips, tricks, or advice are appreciated thanks.