anyone flushed their tranny?
 

so bmw says tranny fluid is life time. i dunno, how would u feel if bmw starts to say engine oil is life time? or brake fluid?

to flush or not to flush? also i heard that some people say the dealer actually doesn't flush all the fluid. just 50% or something like that. hmmm... a flush job is $500 so i wonder if i should do it or not. my 09 30i has 60,000kms.

Try the search button. Tons of responses for this subject.

planning to do mine. 70K miles so i need to get at it. seems you can't really get all of the fluid out. the sheet is like $60 a quart and it takes something like a bazillion quarts to fill.

way too expensive but cheaper than a new transmission.

I am a huge proponent of changing your ATF. A 100% fluid exchange.

I would be cautious of any old "flush'.... the only flush I'd consider is one that uses the pumps in the tranny (ie natural flow) to pull in fresh and drain the old.


Or do 3 or 4 repetiive partial drains and fills, to get to the 95+% range.

Lots of posts in E53 I am guessing

A

Transmission fluid is not engine oil or brake fluid. The applications are completely different. Engine oil gets contaminated by byproducts of combustion. There is no combustion in your transmission; if there is, you have bigger problems. Brake fluid is hygroscopic, it attracts water. It doesn't stop being non-compressible, it just gets water in it. No water in your transmission.

Not sure if you really mean flush (ie with a flushing machine) or just drain and fill. Completely different. I wouldn't use a flushing machine. If you drain it, 50% stays in the torque converter. Agree with Ard that 3 or 4 changes will get most of the old fluid out. Gets expensive, though.

There is nothing wrong with clean fluid. However, you are assuming that the fluid in your transmission will contribute to a potential failure. Your transmission could fail for many reasons (sensors, wiring, actuators, seals) that have nothing to do with the fluid.

Lots of seemingly endless debates on here about the pros and cons. I wouldn't do it, personally.

I'll add to JCLs comments.

Other than "combustion byproducts" there are multiple other factors that break down oil or ATF: mechanical stress shears the molecules, and heat directly leads to breakdown.

The argument..er discussion...typically them turns to "so you say don't do it?"...."ever?"... "so, 200,000 miles? Never?"... "oh, Ok then sometime before then?"...

But then the response is "why bother changing the fluid, the ATF will fail for some other reason anyway"

(Did I capture that discussion right? :) )

A

PS Even worse is the whole "Don't need to do it, BMW doesn't recommend it" argument you get from BMW dealerships at 50, 80k miles...then at 105k they say "well, there's a lot of miles on that thing, we'd be concerned that a change at this late stage could stir up issues"...catch 22

Yes, that's pretty close, I'd say.

Agree that shear lowers the viscosity of the oil over time, but friction materials increase it. And the transmission is designed to adapt to changing viscosity. My main point with the combustion byproducts is that this isn't an engine application, that is a flawed analogy. It is primarily a hydraulic fluid application, with a low grade lubrication requirement.

btw what makes ATF fluid so much more expensive? does it have gold molecules inside? lol

Actually, I don't think there's anything low grade about modern automatic transmission fluids. In fact they are amongst the most complex fluids available. Automatic transmission fluids typically contain antioxidants, antifoam agents, viscosity modifiers, antiwear additives, friction modifiers, and seal swell modifiers.

Formulations vary from manufacturer to manufacturer with sometimes subtle differences in friction modifier chemistry. The oxidation resistance of these fluids is especially high, allowing the long service life now generally reccommended by most OEM's.

In addition to acting as a hydraulic fluid, these products also lubricate gears and bearings, and must be able to withstand severely low start up temperatures as well as extremely high bulk oil temperatures particularly in severe service like towing.

The high temperatures ultimately take a toll on the fluids life as byproducts of oxidation accumulate in the form of depleted antioxidant inhibitors and contaminants from the clutch plates, as well as oxidized base oil.

Changing the fluid in a timely fashion cannot help but provide extended component life. Keeping the fluid relatively clean and fresh enables it to effectively deal with preventing the inevitable results that would occur if it was not changed. Reduced wear, reduced deposit formation and superior performance in both cold and hot temperatures is ensured by a proactive approach to fluid maintenance.

So what, every 100,000 miles as the engineers at BMW have carefully determined?


:cool:

Not in my vehicle. I will be changing mine at 50k. One always want to change "good fluid". No sense changing a fluid after it has deteriorated and caused damage-potential or otherwise.

I don't think there is anything low-grade about these ATF fluids either. I just think that the lubrication requirements are not particularly demanding. That is why a straight 5w oil like an ATF works fine. It is a sealed system, with a pressurized oil bath. It is heated when cold, and cooled when hot. All of the other requirements are very specific, and critical, but they are not as related to the lubrication aspect. And when people talk about changing the fluid, they tend to focus on the lubrication requirement.

I do think that the friction modifiers are more critical than you give them credit for.

I also think that the thermostatically controlled heat exchangers in the X5 deal quite successfully with the high temperatures that used to make transmission fluid changes much more critical.

A lot of the transmission failures we have seen reported have been in the transmission valve bodies. Those aren't caused by lubrication failures. Many other transmission failures have been caused by electrical failures, either wiring harnesses, solenoids, or sensors. I suggest that changing the transmission fluid regularly will have little to no effect on transmission life considering these common failure modes. If we were seeing burnt clutch plates and other signs of overheating, I would fully agree with you that changing the fluid regularly would be of benefit.

Agree

Well according to the attached documentation from ZF, maker of the transmission, the severe service schedule including frequent high speed driving, sporty agressive driving, and/or towing says fluid change every 80-120,000 km or 8 years. So in good ole american miles, 50-75k miles with only the proper fluid listed.

Everyone may not fall into that category, but I think it a good idea to be preventative and follow the earliest manufacturer recommended change at 50k miles.

Also interesting to note the recommended fluid is not fully synthetic, but a blend.:thumbup:

Diesaroo, which transmission is in our 35d's?

Well the 6-speed automatic in the E70 is the GA6HP26ZTU. This I interpret corresponds to 6HP26X in the document.

I am not sure of the 8-speed designation, but according to the ZF publication that I posted, they are both under the same interval.

If you want to change your fluid to be as conservative as possible, that is fair. It is your transmission, and your call.

However, you are taking the guidance of the component manufacturer over the guidance of the system manufacturer.

The document says that very high fluid temperatures will age the fluid prematurely, and I fully agree. It then goes on to say that various types of severe service (as listed above) can cause such high temperatures, justifying early changes of the fluid (every 65,000 miles or 8 years). One thing to keep in mind is that BMW addressed the high temperature issue with the cooler that they designed in to the vehicle. We can discuss whether or not that cooler is sufficient I suppose. I would be more worried about high ambients, trailer towing, etc, if that cooler wasn't there. It is because of the total system design (the cooler, the engine software that backs off engine power momentarily to soften the shifts, the torque converter lock-up clutch strategy that reduces heat from the torque converter, etc) that I would look to BMW's guidelines as more relevant than ZF's.

It would be interesting is to see what actual fluid temperatures climb to compared to ZF's application guidelines. If the BMW cooler isn't able to maintain them within ZF guidelines, then the ZF fluid change recommendation would be very relevant. If the BMW cooler is able to maintain fluid temperatures to the design specification, then there is no severe service recommendation applicable.

The thing is, we'll never know. I have never seen a modern vehicle without a transmission cooler. If we can take that as fact, I think ZF is providing the severe service schedule with that in mind.

Now if BMW installed a larger transmission cooler or an auxiliary cooler as part of the tow package, I might be more apt to agree. But they don't. Also, why has BMW not included transmission fluid as part of CBS? This tells me they are not tracking individual fluid condition that may vary widely depending on usage: towing, aggressive driving etc.

Another part of the equation that you have to think about is: who stands to profit if your transmission fails prematurely? I guess you could include ZF since they're providing the transmissions, but I think we would all agree BMW dealers have more to gain.

So, maybe I'm a little conservative, but I count the ZF people to be a little more accurate in this case.

wow every interesting folks. guess i will be changing the atf at 80k kms.

So lets take this conversation to the extreme-

Lets say, for the sake of argument, that we agree that the conditions that are outlined in the ZF document are never achieved in our use. So never high temps, never towing, etc, etc....

The logical conclusion per the document is that the fluid will last FOREVER... how is this possible? It is flat out nonsense. I dont care if it it 100k miles, or 10 years, or 20 years or 50 years.... it is NOT POSSIBLE for oil to last forever. And for BMW and ZF to 'pretend' this is true is disingenuous.

Now, that brings us to the 'space' betwee 'forever' and '8 years or 80k KM'... I believe that degradation and damage to molecules is cumulative, and os not a binary event- it is illogical to imagine that as long as you do not hit those stated conditions that fluid will therefore remain unchanged....


One thing we can agree on is this: vanishingly few of those reading these posts today will own the car when issues with ATF come home to roost. (They will fail for other reasons, or owners will just move on.)

Finally, I am 100% convinced that the "system manufacturer" does NOT have OUR best interests at heart, and is not driven by the primary design control input of 'longest transmission life'. (IMO, they are driven by 'lowest overall ownership cost to first retail purchaser', 'lowest maintenance cost to BMW', 'lowest repair rates to BMW'...etc.)

Say, haven't we been here before?:thumbup:

A

Mercedes has also been through the same thing that BMW is now going through. First it was lifetime, then it was 100k, now I believe it's either every 40k miles or once at 40k and never again. Interesting to note that Mercedes used to offer free maintenance and now you pay for it...I wonder if that change might coincide with changing the fluid at 40k...hmmm...

Good fresh transmission fluid and filter of the correct specification and level done regularly will, all things being equal, give the longest component life...simple as that...

What is really cool is having a very civil discussion about this. That hasn't always happened on threads on this topic.

Using the towing example, BMW has sized their transmission cooler for towing up to 6000 lbs, in high ambients. What percentage of your driving is under those conditions? I think that if BMW offered a larger cooler for towing, then we could reasonably infer that the standard cooler is closer to 'standard conditions'. On other models (primarily E53) we saw well documented examples of a member towing 8000+ lbs over the continental divide repeatedly. No transmission issues in 80,000 miles of vehicle use in that case. So, I have a suspicion that the cooler is adequate.

I think that ZF is simply covering their ass, as many manufacturers would. They don't give specific criteria, they just say that the fluid is good for the life of the transmission, but it is possible for some people to overheat the fluid requiring a change after 8 years.

Agree that BMW isn't using condition based service on the transmission fluid. Given their predisposition to do so on other fluids, including the transfer case, maybe they just can't see the need.

If your transmission fails early, I think the dealer is least likely to profit. Few owners would choose to buy a new transmission when rebuilds are available, and dealers don't offer any repairs, only replacement. They aren't in the transmission business. Dealers won't get the parts and service revenue, and if there are too many failures, they stand to lose sales. BMWNA isn't in the transmission repair business either, they carry replacement transmissions for use during the warranty period, but I don't see them selling many outside of that term. They essentially abandoned that market. ZF is the only one who stands to gain in multiple scenarios, whether they sell their rebuild kits to remanufacturing places working for BMW, or to independents buying kits to rebuilt individual transmissions.

It isn't a bad thing to be conservative about this. If I planned to keep an E70 for 10+ years, I could see changing the fluid, probably around the five year mark.

Disagree that they are saying forever, they are saying the service life of the transmission. If the E70 isn't going to last forever, why would the transmission need to?

Let's analyze the statement "oil can't last forever". Why not? Oil never stops being slippery, in the life spans under discussion. It gets contaminated, the additives lose their effectiveness, and I would agree with you that the viscosity can change. However, viscosity change is probably the last one I would worry about. It just isn't a very demanding lubrication requirement. The viscosity spec is quite wide. And, the transmission adapts to viscosity changes by monitoring shift times, etc. The oil doesn't have to remain unchanged, it just has to remain within the service spec for the service life duration. If they can't design sensors and wiring harnesses installed within the transmission to last 20 years, why would they need to design a fluid to do so? There was surprise expressed above about it not even being a fully synthetic fluid. My point is that given the low demands on it, it doesn't need to be fully synthetic. (It does cost like it, though. Funny how that works).

BMW and ZF care so little about replacing the fluid that the service instructions tell the dealers to drain the fluid, and put the same fluid back in, when repairing the valve body or minor components in the transmission. That takes time and $$ for the dealer, it is a hassle. But BMW would rather the transmission not have to adapt to new fluid. It isn't done to save money on fluid.

And as with previous debates, we both agree that while this is all technically interesting, it comes down to a discussion of how much it matters. There are other places on the vehicle that I would over-maintain, instead of the transmission, for the same investment.

I agree with some of your comments about what is important to BMW. To your points about lowest cost to various stakeholders, which I agree with, I would add protection of the brand name. That is more important to them than service costs, in my opinion. It is why they called and just gave me a new high pressure fuel pump on my 535i, even though the one they installed two years ago (when the original failed) was working great. It would have been cheaper for them to wait for it to fail, but less convenient for me. I don't think that longest transmission life is on their list of criteria, and properly so. I suspect it is 'sufficient' average transmission life. I have worked on Rolls Royce vehicles, years back, and they had many components designed for 'longest possible life'. It cost a lot, in design and manufacturing, and service. I don't think most consumers want to pay that up front when they purchase a vehicle these days.

Yeah, I remember being here before :thumbup:

IMO there is no such thing as free service, with any manufacturer. There is prepaid service, included in the vehicle purchase price.

When BMW changed service recommendations, they also changed transmissions. 5 speeds, 6 speeds, 8 speeds, etc. But some people looked at the new service recommendations and decided that they were retroactive to older models. BMW certainly could have changed service recommendations on past models, but they would have told owners. I have never received such a notification. Maybe others got a letter.

As both of you (ard) have alluded to, I think ownership scope and perspective come heavily into play here as to whether servicing the transmission is worth it or not to them.

If you plan on keeping your vehicle past 100k miles, regular fluid changes should be part of your regimen. If you're the type of guy who trades in after 50k or even after 100k (after the extended warranty expires) then yeah...to you it may not make economic sense to shell out $500 in fluid and filter every 50k miles.

I personally just like to keep what I have running as well as I can for as long as I can, unless all 4 wheels decide to fall off at once;). Call it a LTR, but for me I enjoy knowing about my vehicle. It's hard to become very familiar with it if you trade it in every few years.

As far as the size of the OEM cooler, unfortunately, we are not the designers so we will never know what frequency of towing it was designed for. From my perspective, 80k miles on original fluid doesn't prove anything. I'd like to know how he's doing with that in another 80k miles. 10 to 1 says he's either got a new vehicle or on his 2nd tranny.

That's what the Mercedes dealer told me when we were looking at the ML 320 CDI, but somehow my OTD price on the X5 with "prepaid" maintenance was still cheaper than his ML without "prepaid" maintenance.

So just how long IS the "service life" of this tranny?

Wouldn't that be a spec that owners should be told?

(that latter question being rhetorical)

A

You wouldn't know it by my transmission fluid comments, but my preventative maintenance regime is pretty solid. Experience as mechanic, mechanical engineer, and 25 years in industry working on maintenance for much of it (heavy equipment, not automotive), as well as my pride of ownership (treat it right, etc) means that my vehicles are over-maintained. They just won't get new automatic transmission fluid. And that is despite the fact that the fluid would be wholesale, the labour is free, and I can use a shop hoist. My intermediate oil changes on earlier BMWs I owned were out of respect for the machinery, and in spite of the fact that I knew I would be selling each of them at the four year mark (we don't have extended factory warranties here).

I think it does mean something if it never overheated the fluid. I evaluated the duty cycle, not just the total miles. Crossing the Rockies multiple times pulling 8300 lbs of Airstream, with the standard transmission cooler, would cause overheating if the cooler was not sufficient for that particular service. Now overlay standard usage on that experience (albeit with an earlier model E53)

I never did like rhetorical questions :rofl:

I would break it down into two categories, the service life due to wear out (as evidenced by worn clutch plates, etc) vs early failures due to random events.

I think that the service life due to wear out is many hundreds of thousands of miles. Look at all the transmission overhaul posts that have lines like "the clutch plates were surprisingly good, and we reused all of them". Those transmission weren't worn out. You can apply predictive maintenance strategies to wear situations. You can do fluid analysis to alert you to impending failure. There are lots of tools at one's disposal.

I think the service life due to random failures of sensors, wiring harnesses, spring clips, actuators, o-ring seals, etc is far less, and is far more relevant. It is also very random, there is no normal distribution. And you won't affect it much if at all by changing the fluid early (with the possible exception of the o-ring seal example).

The above is why I disagree with the theory that these transmissions seem to run about 100,000 miles. Mathematically, that may be the case, I am not sure of the actual number. But if they fail anywhere from 15,000 miles to 300,000 miles (which they have, just from the small sample of members here) then it doesn't help to think about the 100,000 number because you can't readily influence it.

I feel the same way and do my best to respect my machinery and treat it right. Did you do any towing with your vehicles? Even if you did, your relatively short ownership experiences would not likely be long enough to test your transmission maintenance (or lack thereof) plan.

Older german automobiles get a second life in the 3rd world (usually Africa) and they are run into the ground, but despite this abuse, they seem to soldier on somehow. Just because the machine is overdesigned doesn't mean it should be abused, even though it is still "running fine" IMHO.

I bet if you did an transmission fluid analysis of the E53 that crossed the rockies pulling the airstream, it wouldn't be very pretty.

Back to an earlier comment you made referencing the ZF document that ZF was covering legally themselves, I don't think they were at all. It is a document written by the component supplier, most likely an engineer that simply gives a warning not to expect too much from a single fill of fluid.

They probably didn't think that vehicle owners would be reading it. Always in life there is a struggle between the businessmen and engineers. Most of the time, the engineers' concerns are silenced under the guise of "good business", but if you look carefully you can still find the honest opinion of the designer...

I'll add something else to the pot that has not been discussed. We've been debating to no end the life of fluid etc., but has anyone considered the life of the filter?

I don't know the specific design of the ZF filter in question, but on many cars, the filter has a very similar design to the engine oil filter in that it is designed for bypass flow conditions. In other words, to maintain flow when the fluid is cold, the fluid is not filtered and goes through the bypass valve, until the fluid is at operating temp. and then it is filtered normally.

After 100k+ miles on the original fluid and filter, the filter may be choked with metal and clutch material to the extent that to maintain fluid pressure, the transmission operates in 100% bypass mode. This would mean that unfiltered fluid with metal particles and clutch material would be circulating and building up in the valve body and other sensistive components causing accelerated wear.

My advise… if the tranny is not giving you any problems ... Don't touch it.

I would agree at high mileage, if regular service has not been performed, it's better to save money for a new car or for a new tranny. Often the only thing keeping the torque converter from slipping is the added friction from the suspended metal particles in the old fluid.