OK I did transmission fluid flush on my 02 4.4i

[upallnight]

Since most of the containments in ATF is the semi-metallic material from the clutch packs I would say that replacing ATF is a preventative measure. The electro servos in the trans are nothing more than electromagnets which causes the valves to open or close. Having all that semi metallic material in the fluid will be attracted to those servos, that is why the manufacturers installs permanent magnets in the pan to attract those material and prevent them from circulating through the trans.

The manufacturers of the trans used in our X is either Zf or GM both recommends ATF fluid changes, only BMW in order to reduce their "Free Maintenance" cost to owners call the ATF Life time hoping that the trans will not crap out before the warranty.

[Multibeemer]

I agree that eventually, the contaminants in the fluid will cause problems with the transmission. I'm just not convinced this will on average happen before other components not related to the fluid, such as the clutch packs, wear out.

I'm not saying it's a bad idea to replace the transmission fluid, and in some cases, it might increase the life of your transmission. But I'm with JCL that in most cases, it won't really do much, if anything. It definitely didn't in the case of my daughter's E46. Otherwise, as I said, there would be thousands of cars in this country with dead transmissions, when in fact, transmission failure really isn't that common of a problem.

[JCL]

Originally Posted by upallnight

Since most of the containments in ATF is the semi-metallic material from the clutch packs I would say that replacing ATF is a preventative measure. The electro servos in the trans are nothing more than electromagnets which causes the valves to open or close. Having all that semi metallic material in the fluid will be attracted to those servos, that is why the manufacturers installs permanent magnets in the pan to attract those material and prevent them from circulating through the trans.

The manufacturers of the trans used in our X is either Zf or GM both recommends ATF fluid changes, only BMW in order to reduce their "Free Maintenance" cost to owners call the ATF Life time hoping that the trans will not crap out before the warranty.

And once that semi-metallic material goes into the pan it either sits on the magnet, or stays on the dirty side of the screen. In both cases, it does no harm there.

If the reason for not changing fluid was because of the prepaid maintenance offered in the US, then it would follow that all the rest of the world, with no prepaid maintenance, would have a different recommendation, namely to change the fluid. But they don't. And if BMW was concerned, then they wouldn't be holding the lease residuals on all those leased vehicles, without reducing their exposure.

What is different with BMW and those same transmissions in other vehicles? The transmission cooling system. The control software that reduces power during shifts. The torque converter lock-up strategy. The transmission monitoring algorithms. Etc, etc. That is probably why those two manufacturers endorsed BMW's maintenance strategy.

[upallnight]

Do they really endorse BMW's maintenance strategy or do they just want to sell transmissions to BMW? After all when the trans crap out, do ZF or GM repair the trans or do BMW perform the repairs?

[jgold47]

I'm on the fence with this. I've had very few automatics, but my e36 has 160K miles with no service records showing a tranny change. Unfortunately, its weeping a little bit, which means I may need to drop the pan and re-do the gasket. I'll probably do the filter at the same time and top it off, but I dont think I am going to do a full change.

I keep reading threads where people do the tranny service at high mileage and then 6 months later the tranny dies. I've read that the clean fluid does too good of a job cleaning the engine and the gunk it dislodges causes the passages to clog.

[mysweetx5]

That you tried to make a point on changing the transmission fluid
but at the same time, you plan on messing things up by doing basically
the same mistake a few people be doing outhere. By: topping-up and
not trying to add as much fresh fluid as you can, & not changing the filter.

By doing so, you risk to cause more damage because (the pan needs to be
dropped in order to be cleaned, including the 4 magnets inside).
If you knew how dirty they get over the time, you would be more excited
to clean them, because this is where all the wear metals seated.
The previous job upthere in this forum with the blue X5 4.4i was from me.
meaning: that may tell you something that I'm aware of because I've been there

I did mine for the 1st time at 125,000 miles, now I'm still driving strong
the same way with nearly 128,000 miles now. My suggestion is just that
Don't just top it up! Do it the right way, by removing as much dirty fluid
you can pull out. And Fill-up with the proper fluid, and replacing new filter.

[Hoser]

There are not many companies around that know more about automatic transmissions than Allison. They had to come up with new oil formulations when GM dropped certification of Dexron. When that happened everyone was open to put burro pee in a can and call it dexron. The engineer who wrote the specs on Allison's replacement synthetic Syntec when retired, joined an RV forum about Allison. They were forced to re-adjust their thinking about lifespan of trans fluid-even with their new super juice. To those who "know" someone who changed their fluid/fliter in their automatic and ended up blowing up their trans- I think I would challenge them to name names. It only stands to reason that removing any of the dirt and byproducts of a piece of machinery with friction surfaces and replaceing the lubricant with fresh new lubricfant, can only do good for the same reason it does in an engine. I doubt that any machine manufacturer has their own oil well, oil research section, testing labs, health & safety standards approval section (this stuff is in human contact). I think it is safe to say BMW and others use rebadged cans of lubricants and chemicals. The fact that Ford uses the same ZF6HP26 tranny in a Lincoln Navigator and specs Motorcraft Mercon SP fluid at $8/liter should be a little enlightening to those who are receptive.

[JCL]

Originally Posted by Hoser

There are not many companies around that know more about automatic transmissions than Allison. They had to come up with new oil formulations when GM dropped certification of Dexron. When that happened everyone was open to put burro pee in a can and call it dexron. The engineer who wrote the specs on Allison's replacement synthetic Syntec when retired, joined an RV forum about Allison. They were forced to re-adjust their thinking about lifespan of trans fluid-even with their new super juice. To those who "know" someone who changed their fluid/fliter in their automatic and ended up blowing up their trans- I think I would challenge them to name names. It only stands to reason that removing any of the dirt and byproducts of a piece of machinery with friction surfaces and replaceing the lubricant with fresh new lubricant, can only do good for the same reason it does in an engine. I doubt that any machine manufacturer has their own oil well, oil research section, testing labs, health & safety standards approval section (this stuff is in human contact). I think it is safe to say BMW and others use rebadged cans of lubricants and chemicals. The fact that Ford uses the same ZF6HP26 tranny in a Lincoln Navigator and specs Motorcraft Mercon SP fluid at $8/liter should be a little enlightening to those who are receptive.

TwinTurbo made a good point, above, but I don't want to let your points go unchallenged.

I can point at specific transmissions whereby the fluid was changed, and the new fluid (or more specifically, the detergents in the new fluid) caused a failure in a transmission that was up to then, performing well. These were customer transmissions. They weren't BMWs (but then, BMWs don't have BMW auto transmissions). You can't have their names. You don't have to believe me if you don't want to, but these are not old wive's tales or urban myths. It certainly doesn't mean that changing the fluid at higher mileage will always cause a problem, it simply doesn't. But statistically, it does cause a problem often enough to make shops stop and think about whether they want to take the risk. Many won't, as they don't like being on the hook for a transmission rebuild after they specifically recommended not changing the fluid (same as the vehicle manufacturer), but did it at the customer's insistence. It is more profitable for them to pass on the revenue from the fluid change, and avoid the risk of the occasional rebuild on their dime.

I don't understand your Allison reference. Great company, no worries there. But they were owned by GM Powertrain from the 1920's to sometime in the early 2000's. So, Allison is GM. And GM endorsed BMW's maintenance strategy. So I don't think that their heavy truck experience, as applied to RV's, has any weight here.

The other issue with RVs is that they are famous for being heavier than they should be according to the GVW sticker, and having more aerodynamic drag. Both stress transmissions. I can understand changing the transmission fluid in a vehicle that is regularly overloaded, as many RVs are. It would make sense, as it would shift the risk/reward balance.

You mention dirt and byproducts in a transmission. Fair comment. But a transmission fluid has very low demands for lubrication. That is why it isn't called transmission oil. It is a hydraulic fluid, first and foremost. It is a heat conductor, very important. And it can't foam or oxidize. But the lubrication demands that it is subject to are so low that auto trans fluid is typically a straight 10w oil. It is running in a sealed system, with pressurized lubrication, with no external contaminants (things like byproducts of combustion, water, etc). So, it lasts a long time as long as it doesn't get burnt. Thermal management is very important (back to the RV issues....).

BMW doesn't design or build auto transmissions, or the fluid that goes in them. ZF and GM do a good job of both (and both have their fluids built to their own specs). What BMW does do is alter the control strategies, and the transmission cooling system. Those are BMW items, not ZF or GM (although they are done in cooperation). Items like the BMW cooling system, with the thermostat (keeps it cool, even towing 7700 lbs in Europe, and provides warm fluid sooner on startup to reduce cold wear), and the strategy of backing off the power via the ECM when shifting (reducing clutch wear, and heat, significantly) both extend the life of the transmission fluid. Even more important, the lock up torque converter strategy (much reduced heat when locked up) helps a lot. Not sure what the Lincoln has in this respect, but to say that it is the same transmission is incomplete.

I wouldn't use the Mercon fluid in a BMW, but that is simply because while it is similar, it isn't necessarily the same. ZF went to specific fluids due to their transmission design, primarily relating to clutch engagement characteristics. That is all that is different about the different fluids, at the end of the day. Unless ZF or GM want to publish their friction specs, it is a mugs game to say that the fluid is the same because some parts of the transmission are the same.

Your subsequent post asked about pumping out the transmission via the return line from the cooler. This can certainly be done. It gets more of the old fluid out. If I had a transmission with burnt fluid in an RV (common occurence, for reasons listed above) I would do this. But I wouldn't do it on a modern BMW, unless the fluid was burnt. Take a look at the BMW service procedure. If a tech has to drain the fluid to change a simple item like a temperature sensor, speed sensor, or whatever, inside the transmission, the approved service procedure says to catch the old fluid and put it back in. Think about that. It's a lot of trouble. It would be easier to put new in (and thus cheaper, when you are paying labour by the hour). But they want to keep the old fluid in, because it is better for the transmission than new fluid. There is a paradigm shifter for you.

Always happy to talk transmissions. And I even know where Stettler is (ex Edmonton, and Grande Prairie).

Cheers

Jeff

[TwinTurboGTR]

Good morning. The last time anyone posted on this thread was Dec. of last year. While your information is concise and well written, the topic has been beaten to death. There is a consensus from other members and former techs on this forum that support you don't touch the tranny if it has hit 100k and has never been cracked open before. Using the old adage of "if it ain't broke..." The exception would be if the tranny is experiencing problems, then change fluid. You may be looking at an overhaul of the tranny anyway, so as a last ditch effort to squeeze the last bit of life out, you could drop the pan and change the oil and filter, but end result normally is the same.

[sunny5280]

Originally Posted by TwinTurboGTR

Good morning. The last time anyone posted on this thread was Dec. of last year. While your information is concise and well written, the topic has been beaten to death. There is a consensus from other members and former techs on this forum that support you don't touch the tranny if it has hit 100k and has never been cracked open before. Using the old adage of "if it ain't broke..." The exception would be if the tranny is experiencing problems, then change fluid. You may be looking at an overhaul of the tranny anyway, so as a last ditch effort to squeeze the last bit of life out, you could drop the pan and change the oil and filter, but end result normally is the same.

Consensus doesn't prove anything. I'm in the camp of changing the transmission fluid. I had it changed in my 2001 4.4i with 108K miles (right after I purchased the vehicle) and drove it to 129K miles before buying my current X5. Never had a hint of problem with it.

I had it serviced at an indy who specializes in German vehicles and the owner hsa over 25 years working as a mechanic and service manager for BMW / Mercedes before opening his own shop. It has been his experience changing the transmission fluid does not result in increased failure rates. To date I have seen no supporting facts showing an increase in faliure rates for transmissions where the fluid was changed after high mileage. Until such time I'm chalking this up to a wives tale.