Originally Posted by S62MPOWER
This is a late addition, and I think it was said, but ZF, the transmission manufacturer, recommends 60K miles, more often for severe service. It's on their website. My experience is when changed with a BMW or ZF factory filter (don't use anything else) these tranny's perform great, my 95 740i has had 3 changes with 275K miles (1 Redline ATF and 2X Valvoline MaxLife DEXRON V. Maxlife is a BMW approved DEXRON V and relatively inexpensive. Also in the family; A 2005 X3 w 155K miles has had two changes with Val MaxLife, it too shifts like a champ.
Dealer gave me the same BS when I went to buy the trans filter on the last change for the 740. He said I didn't need to do the change, I said, "Yes I do, this is the third change, and it's got 270K miles and shifts like a champ" He said, "Oh" and went in the back and retrieved the filter. How can someone say it doesn't need attention when they don't know mileage and history? Naive and misinformed.
The reason for the dealer attitude is a very long story, but has it's roots in marketing and environmental goals at BMW. BMW, Texaco and ZF, iirc, pushed for extended drain intervals and better mileage beginning in the early 90's with synthetic technology prior to to the DEXRON V specification. They went a bit too far and a lot of misinformation was propagated throughout the dealer network and independents (I'm being nice) and it still survives to this day. There were lots of transmission failures, many shortly after a fluid/filter change. Dealers and independents became "gun shy" as they couldn't reliably predict the effectiveness of a transmission fluid service, particularly after 100K miles. Importantly, the ZF procedure for properly filling the transmission was frequently done improperly. I myself had a mechanic with a good reputation shortfill a tranny in my friends 2001 540I by 2 1/2 quarts!!!! And on it goes ....
The charts for figuring out what fluid to use in the transition years to the newer specs were complex and confusing to read for the average Non-BMW mechanic, involved colored tags on the transmissions and BMW started using words like "Use of improper fluid will cause Transmission Failure". All these issues and some others created the confusion and spread of misinformation and the reluctance of dealers and indies to service BMW transmissions.
Another poster said that techs will "save and refill" trans fluids. That is a holdover from the old days when the fluid was really expensive. Factory fluid, now that it's all DEXRON V, is reasonably priced again, and should be renewed anytime you drain fluid.
Why risk contamination on such sophisticated German hardware?
More accurately, waiting till 100K miles or more to change your fluid will dramatically increase your likelihood of transmission failure, duh. Like anything else, once the nonce of the ZF fill procedures are understood, the service is fairly straight forward.
A previous poster is correct, BMW recently changed lifetime to 100K miles, which again, is 40K miles past ZF's recommendation. I use the same 60K rule of thumb for the French-built GM transmissions. (very different from the US GM automatics)
The great news is DEXRON V spec fluid supersedes all, so use that, change it at reasonable intervals and life is good. For DEXRON III boxes, I like RL ATF, but the 740i shifts excellent with the Valvoline MaxLife DEXRON V.
THANK YOU poster that recommended a resetting of adaptions, brilliant, I had forgotten that is part of the routine on a center diff fluid change on BMW all wheel drive vehicles; The computer controlled "clutch take up" position is reset to adapt to wear.
BMW Transfer Case Fluid (TCF) is high-tech stuff, should also be changed before factory recommendations (the repairs for TC's are EXPENSIVE!) but Volkswagen/Audi has the same spec fluid and there are less expensive alternatives to BMW like Ravenol's TCF.
With TCF, SHAKE THE BOTTLE REALLY WELL, additive bits settle to the bottom of this product.
Hope that sheds some light
A lot of DIY'ers still have difficulty changing out the fluid on these units due to the location of the fill hole and the temps requirements. Underfilling is an issue because they either can't pump in what they measured which came out or the trans temp exceeds the max when refilling.
Oh and BMW techs still save and re-use fluid when working on the transmission.
https://bmwtechnician.com/2018/07/12/zf-8-speed-transmission/
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