Originally Posted by macneil
Hey, I've got a 92 325i auto. I was thinking of getting the transmission fluid changed but then i was told that bmw puts in a lifetime fluid and that i shouldn't get it changed because it wouldn't do it any good.
I was told this by a mechanic that works on bmw's.
More myth and misconception surrounds automatic transmissions than almost anything...
1. BMW USED TO HAVE
'lifetime fluid' but have stopped doing that and gone back to servicing them. They were also very quiet about doing this, for obvious marketing and corporate image purposes. I do know under a normal schedule it would be due to be changed at least one time by 100,000 miles. (Not sure since you didn't list which transmission you have.)
2. Be absolutely sure you are using the CORRECT FLUID
for your transmission. BMW lists at least four kinds across the board. This could take some research to find out. Check the pan bottom, there should be a label.
3. In any transmission make, heat is the mortal enemy. However there must be enough friction to make the clutch packs engage - hence, they're engineered for a happy medium. Friction and heat cause the fluid to break down - causing more friction and heat - causing more fluid to break down. See where this can go if you do any towing or drag racing?
4. Changing will NOT harm the transmission, it will preserve it. The myth of "changing fluid will kill it" came from the Detroit scrap iron mentality. ie: 'Leave it in there until it gives you trouble.' BY THE TIME IT GIVES YOU TROUBLE (starts to slip, flare or shudder) THE FRICTION DISKS ARE NEARLY GONE AND IT'S TOO LATE FOR A FLUID CHANGE TO HELP. It is NOT from; new fluid burning the clutches, new fluid dislodging dirt or the transmission computer and/or valve body 'recognizing' new fluid and not knowing what to do with it. CHANGE IT BEFORE IT GIVES YOU ANY PROBLEMS.
The good news is changing your filter and fluid isn't that difficult but remember to check the level warmed up and running. If you don't have a dipstick MEASURE HOW MUCH COMES OUT AND PUT BACK THE SAME VOLUME of correct fluid, preferably at the same temperature.
Also, look up and do some reading on Mario Esteed of ATSG (automatic transmission service group) in south Florida.