no, you don't have to drain the tranny... you just take the boot off... replace the bearings.... pack it full of grease.... and seal the boot back up.... easy as that.... i had to repack the bearings in my drivers side one when i put my camber kit on. i let the assembly rotate too far out when i took the upper control arm loose to put it on. the CV joint seperated.. it sucked... it was messy as hell... but it's good as new now