I removed my dipstick tube & put on a new O ring & resealed it with rtv & still leaked until I dropped the pan & took off the tube again & cleaned up the recess where the tube fits with brake clean & same with the end of the tube, regooped it again(with permatex #2 my fav) & no leak after that. If it's not clean & dry the ATF just wicks around whatever kind of gasket sealer you use & leaks again. good excuse to ch the fluid/filter & adj the band