anyone flushed their tranny?

[diesaroo]

Originally Posted by ard

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?

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...

[JCL]

Originally Posted by diesaroo

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.

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.

[JCL]

Originally Posted by ard

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?

A

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

[JCL]

Originally Posted by diesaroo

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...

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.

[diesaroo]

Originally Posted by JCL

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.

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.

[diesaroo]

Originally Posted by JCL

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.

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.

[ard]

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

[JCL]

Originally Posted by diesaroo

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.

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).

Originally Posted by diesaroo

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.

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)

[JCL]

Originally Posted by ard

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

I never did like rhetorical questions

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.

[diesaroo]

Originally Posted by JCL

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 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...