ONLY USE THE CHRYSLER/JEEP SPECIFIED TRANNY OIL...ITS NV3500/3550 SERIES TRANSMISSION OIL. IT IS NOT CHEAP, if I remember correctly it only takes two quarts, buy 3...so $30-40 IS MUCH CHEAPER THAN A UNINSTALL AND REBUILD. All of the NV series trannys require special tranismission oils. I remember someone, I think on Bfix a couple of years ago, said they blew up their tranny; then asked what kind of oil others were using...they apparently didnt think it was important to listen to the warnings about only using the correct spec-ed oil...expensive mistake. Good luck....you will love the tranny.