I have heard you should not change the transmission fluid ever. But my 2003 x5 with 158,000 miles on it still has the original transmission fluid. Some shops have told me if I change the transmission fluid I might cause the transmission to stop working correctly. Does anyone have experience with this and have a recommendation?
I don't recall when BMW started with the 'lifetime' fluids thing, though I thought I'd heard/read in the last couple years or so BMW had backed-away from that, in part or wholly. Moot point for your car though - What I've heard is similar to what you have - if at this mileage you change the trans fluid, the stirring up of debris/dirt/whatever somehow can kill the torque converter. (I'm assuming yours is an automatic, as changing fluid with manuals 30-60k is standard maintenance). My mother had a '96 E38 and the auto trans went out @ 105k, so I'd be thinking at 158k there's reason to think yours may be on 'borrowed-time', per-se, but, I don't think we have any good way to assess every variable determining longer or lesser trans life either. Me, i'd probably continue with the if-it-ain't-broke etc. etc. but be ready to accept the potential inconvenience if the trans were to fail, and more importantly, be ready for the unexpected expense the (likely, maybe more) $6k a trans replacement would cost in parts and labor. It was $5k+ for the E38 at the time, which was more than 10 years ago now. If you do end up replacing the transmission someday, then for the new trans I'd say do a trans fluid flush/change every 30k as preventive maintenance. If anything with the trans starts acting wonky, offhand I'd guess that would be a pretty good indicator failure is imminent - if all's good though, that's great, keep on-a-pluggin'!
