Like I said, you have open diffs The factory reccomends 75W90 for these, but personally, I would use the 75/140 fully synthetic anyway knowing the Jeep's appetite for diff bearings. As far as transmission fluid is concerned, only ATF+4 will do. Chrysler transmissions user different friction materials to GM and Ford, and so Dexron and Mercon fluids will not do. Valvoline and Mobil do make ATF+4 compatible fluids but I don't know how easy they are to find in the UK aftermarket.