Lazy man's tranny fluid maintenance
 

Rather than the labor intensive process that changes ALL the oil is there a down side to just draining what will come out by removing the fill and drain plugs then adding fluid to refill to the proper level?
It seems if we do this annually it would keep the fluid fresh and maintain the additives. By the time we reach 100,000 miles it would have been done maybe 5 times.
Thanks
Rick

You are looking at about 4-6 hundred in fluid for 5 changes. I'd pass and just run the original fill till it dies. There is no data that supports frequent fluid changed will extend the life of these transmission, in fact if you speak to a ZF authorized service center they will tell you to leave the fluid alone.

Much is said about what BMW means by lifetime fluid and it's really quite simple Lifetime means the lifetime of the transmission not the cars lifetime or a humans lifetime. If you get 90k or 180k there is no need to change the fluid. A few of the later transmission have a service interval but that was added due to the confusion over what "lifetime" meant.

What has changed about the transmissions or fluid in them that makes them not benefit from any fluid change at all versus the not-so-distant past when BMW recommended ATF changes as frequently as every 15,000 miles?


MG

I have no idea, but fluid can cost up to 25 bucks a liter and I can get Dex 1 or 11 for a couple bucks at the local autoparts store. so thats different. The old 3hp and 4hp transmissions were great but hardly the level of a modern trans. We use to change oil ever 3 k too and thats long gone. change it if you want, but there is nothing that indicated it does anything but empty your wallet. I would challenge anyone to produce data that shows a benefit in frequent changes for late model BMWs.

If you are constantly changing the fluid without changing the filter, your filter will get more and more clogged, which could lead to a loss of fluid pressure.

It is not hard at all to drop the pan and replace the filter.

http://www.xoutpost.com/bmw-sav-foru...ed-bmw-gm.html

In very general terms, what has improved over the past decade is programming that provides firmer shifts (less resulting heat and clutch wear), better transmission cooling, and more experience on the part of BMW as to fluid breakdown over time. However, that is all a side issue. It isn't about whether the fluid is better if it is new, it is about whether new fluid will extend the life of the transmission. I don't think it will. Transmissions will fail for many reasons, but old fluid hasn't been shown to be one of them. You would probably be better served by replacing all the sensors inside the transmission than the fluid. Even better would be to take the money spent on fluid replacements, and put it in a future transmission replacement fund.

Couldn't have said it better myself. Automatic transmissions will fail inevitably just by nature... clutch packs will wear no matter how new the fluid stays. What seems that it would make the most difference is the driving profile as it would be more directly related to clutch wear.

And on a side note, when the clutch discs do wear the clutch material gets suspended in the fluid which thickens the fluid and adds some hydrolic pressure. My last job before BMW was at a trans shop (R&I guy). You'd be amazed of the number or failed transmissions that came in shortly after doing a fluid change simply because the viscosity was lowered, the lubricity was higher, and the clutches just started slipping bad to the point of no return.

I can tell you that on my own personal vehicle, I will not be changing the fluid.

I have to say this is pretty surprising info to me that you won't be changing yours at all. I thought that if you change it frequently enough (say every 50,000 miles) then you will avoid the possible 'disaster' that people describe in going from super dirty to super clean fluid.

It seems to me that like all lubricants, ATF breaks down significantly over time and should be changed. Even ZF recommends changing the fluid and considers extended interval to be 100,000 km / 62,000 miles. Mike Miller in his "old school BMW maintenance schedule" also recommends 60,000 mile intervals (he does btw acknowledge the mysterious breakdown issue with high mileage previously unmaintained transmissions; though honestly I don't see how, at least in theory, this issue shouldn't apply to any fluid changes whether it's engine oil, transfer case fluid, power steering fluid, coolant, etc.) It is widely known that BMW now considers lifetime fill as 100,000 miles, and that is now becoming their recommended change interval. So given all the above I would think a transmission would be less likely to crap out due to stirring up gunk at 60,000 miles versus 100,000 miles.

As a reference just look at the fluids in this link as changed at 91,000 miles and 133,000 miles.

Transmission Fluid change on 5HP24 (A5S440Z) x2:

Directed at Weasel, but since it is an open board....

The usual disaster is caused by any sediment in the transmission being dislodged from a location where it wasn't hurting anything and then clogging a valve body orfice, as an example. Changing the fluid more frequently means the transmission will have less contaminants each time to be disturbed, but it also means you will be doing it more frequently, thus increasing the odds of a failure following a fluid change.

I think Weasel (and the Cleaner) are saying the same thing as I have always said; while clean fluid is good (in a motherhood kind of way), lack of transmission fluid changes in BMWs with either ZF or GM automatics hasn't been reported to cause any failures. In fact, unscheduled transmission fluid changes have reportedly caused failures. Those of us who worked in shops on transmission tended to leave them alone, unless we found burnt fluid or other symptoms of overheating and fluid breakdown.

It doesn't mean that people shouldn't change transmission fluid if it makes them feel good, feeling good is important. They just shouldn't equate the fluid change with an expectation of longer transmission life.

All of the above IMO.

JCL hit it pretty good :D And in my non BMW experience from previous shops was that the clutch material in the fluid added some viscosity and changed the friction profile of the fluid, so when people changed all the fluid of an older, higher mileage car the transmission would inevitably start slipping. (I'm sure not being able to reset the trans adaptations with the fluid change didn't help)

I've personally seen more transmission failures on transmissions that have been serviced than one ones left alone. And since I got the vehicle with over 80k miles, I couldn't see any good coming of a fluid change. Now with over 90k miles it still drives perfectly and I'm waiting to see how long it will go before I have to go all swissfrank on her ass.