austinholloman

I changed the tranny fluid in my E36 M3 at 115k miles for the first time in its life. Its a ZF 5 spd. I am now at 125k and have had nothing but smooth sailing. It was night and day different after the pan drop and refill. I did do it twice in a row to be safe. On my C43 I do it every three motor oil changes just to be safe.

lclarkc32

I'm a little bit confused. Is it sufficient to just do tworotorturbo's procedure as described in the head post, or is it also necessary to drain and refill the ATF fluid via the ATF pan (pan drain, gasket and filter replacement)? tworotorturbo mentioned that it took about 8 qts of ATF fluid to get clean, new ATF fluid coming out of the upper ATF hose. But since there's about 14 liters of ATF fluid in the system, that leaves about 6 liters of old ATF fluid. So, to do a full flush and replace, is it better to drain and replenish the fluid in the pan first, or last? It seems like doing the flush procedure as outlined would pump the old ATF fluid that is still in the radiator into the ATF pan, so if you drain and replenish the ATF pan first, you would get old ATF fluid mixed into the new fluid. OTOH, if you drain and replenish the ATF pan last, you would be draining and throwing away some new ATF fluid. It just seems like there isn't a good way to get all the old ATF fluid out of the system without mixing a half-dozen or so liters of it into new ATF fluid in the ATF pan. Maybe the only way to remove all old ATF fluid and replenish with new fluid would be to find a way to introduce the new ATF fluid into the upper ATF radiator inlet as you are pumping out the old ATF fluid via the upper ATF hose. Does any of this make sense? Am I over-thinking it?