I have an 01 XJ i want To change the rear diff fluid i think its the Chrysler 8.25 rear so Whats the proper fluid is it 75w or 80w90 GL5 and is the front diff the same? Also is it better to Buy a new gasket or use hight temp copper RTV on the cover. And one more thing im gonna change the T case fluid while im at it a 231 i believe is dexron III ATF the correct fluid. Any info is appreciated thanks.