Let's talk Transmission Maintenance...

[ard]

What kind of maintenance should we perform on our transmissions if we wish to have the LONGEST LIFE POSSIBLE?

I know there will be a school of thought that it is "Follow the BMW recommendations, they know best"... hopefully we will get past that nonsense quickly. Previously BMW had said "lifetime". This is intellectually, and factually, indefensible. So they made it "100,000" which is after their longest possible extended maintenance contract...

But if the discussion comes back to "BMW Recommends", can we ask "What is it about a BMW Automatic Transmission that makes it immune to ATF degradation and internal wear?" (Remembering that ATF sitting for 4 years with zero miles will degrade...)

My belief is that ATF changes, at regular intervals- say 30-40k miles, will ensure that any mild contamination due to particulates is removed, and fluid that has been sheared down due to heat and mechanical stress is changed to fresh fluid- which will protect the tranny for the long run.



Can we also get past the 'transmission flush bogey man' of 'solvents and reverse power flushing causing blockages and internal damage'??? I am just talking FLUID CHANGE. Drain old, insert new.

Comments?

What I really want is technical input, not "my SA said" or "the manual says"....



A

[JWoody]

HHhhhmmm, this is a good point. My MKIV VW GLI is a daily driver with a 6SPD manual tranny, but I do 40K tranny oil changes with AMSOil. I believe in what BMW says for their vehicles, but I am considering doing 50K Tranny changes for our X5. But I plan to use BMW's oil vs AMSOil. Just my .02...

-J

[JCL]

OK, I'll bite to start it of. Carrying on the discussion from previous posts....

I would recommend you maintain the transmission cooler, and have transmission software updated if there are specific issues with shifting that software upgrades have addressed.

My lack of support for changing the fluid is not because "BMW said" but rather because I see little benefit to changing it, and a small but real risk. The risk of damage is slight, but it exists. At the same time, I think that the transmission is likely to fail from non-fluid related causes prior to the fluid degrading to the point that it causes a transmission failure itself.

Ideally, transmission maintenance would consist of a teardown and inspection at midlife. I just don't think that plan is economically practical, it is better to run it to failure for most owners.

The risk of transmission fluid changes that I refer to is not due to power flushing, which I wouldn't do. It is simply from draining and filling. I have never used a power flush, but I am familiar with them. When you drain the fluid, you leave the valve body and actuators low on fluid. When you start it up after adding new fluid, you go through each gear to fill up all the clutches. That is what can disturb sediment that wasn't otherwise hurting anything, IMO. You have also added a fluid with different viscosity (thinner, most likely) and with different friction characteristics. The transmission has adapted to the fluid it had, but must now adapt again. None of this means that every transmission fluid change will cause a problem, just that too many transmissions have been brought in for repairs after a recent fluid change, and when prompted the owners acknowledged that the transmission was shifting fine until they changed the fluid. These cases are entirely separate from those that had a shifting problem, and new fluid didn't fix it (what I would call the faint-hope clause).

What is different from many years ago when transmission fluid changes were recommended by all manufacturers?
1) Fluids are far better. Synthetic or not, they have better additive packages that are more stable, and which thus last longer.
2) Transmission coolers, thermostatically controlled, are far more common. We used to put transmission coolers on vehicles that were towing, and some heavy duty applications had them standard, but they are now much more sophisticated.
3) Lock up torque converters have become commonplace, primarily for reasons of fuel economy. Heat is the biggest enemy of transmission fluid, and that heat comes largely from the torque converter. When it is in lock-up mode, there is no significant heat being produced. Long transmission life will be promoted by driving habits that keep the torque converter in lock-up mode, particularly when towing.
4) Electronic controls have become commonplace. Computer algorithms are managing the shifts, preventing shifts that would stress the clutches too much (ie high speed downshifts), and they are causing shifts to be much crisper (less clutch slip, less heat). In the old days, a "shift kit" simply firmed up the shifting via stronger springs or different check valves in the valve body, and that was a standard part of a performance upgrade or a towing package. It has gone one step further, in that engine management computers are integrated with transmission control computers. By backing off the timing when the shift happens, power is momentarily reduced, lessing the shock on the driveline. That is why those fullpower shifts are made so smoothly.

All of the above promotes longer fluid life. Will it last forever? Of course not. But will it degrade slowly enough such that something else will break before the fluid is unserviceable? That is what BMW is essentially saying. I agree with that, but based on my experience more than any blind faith in BMW maintenance recommendations.

There are members here with transmissions far beyond 100,000 miles, on the original fluid. What that really means is that other things haven't broken yet, and the fluid has just soldiered on.

If owners do want to change their transmission fluid, I think that is fine. I wouldn't, but that is just me. If owners do change it, I would use BMW recommended fluids (no aftermarket fluids), a new filter, and a very careful adherence to the BMW procedure for getting the correct amount of fluid in it, using a thermometer to determine fluid temperatures while setting the level.

Anyway, my quarter is up. Time for someone else to offer up counter opinions.

[ard]

Originally Posted by JCL

OK, I'll bite to start it of. Carrying on the discussion from previous posts....

I figured one thread would be better.,

Originally Posted by JCL

I would recommend you maintain the transmission cooler,

Did not see a 'cooler maintenance' in their schedule...nor do I think such a thing exists. Clean the fins??? that kind of "maintenance"?

Originally Posted by JCL

and have transmission software updated if there are specific issues with shifting that software upgrades have addressed.

Sure, but that isn't maintenance, it is "Service" based on specific issues.

Originally Posted by JCL

My lack of support for changing the fluid is not because "BMW said" but rather because I see little benefit to changing it, and a small but real risk. The risk of damage is slight, but it exists. At the same time, I think that the transmission is likely to fail from non-fluid related causes prior to the fluid degrading to the point that it causes a transmission failure itself.

If you can show me ANY data that supports a "100,000 mile, unlimited years" lifetime on ANY ATF, you get a beer.

Originally Posted by JCL

Ideally, transmission maintenance would consist of a teardown and inspection at midlife. I just don't think that plan is economically practical, it is better to run it to failure for most owners.

That is disingenouos at best. A TEARDOWN as a maintenance?!?!? Come on, lets be rational

Originally Posted by JCL

The risk of transmission fluid changes that I refer to is not due to power flushing, which I wouldn't do. It is simply from draining and filling. I have never used a power flush, but I am familiar with them. When you drain the fluid, you leave the valve body and actuators low on fluid. When you start it up after adding new fluid, you go through each gear to fill up all the clutches. That is what can disturb sediment that wasn't otherwise hurting anything, IMO. You have also added a fluid with different viscosity (thinner, most likely) and with different friction characteristics. The transmission has adapted to the fluid it had, but must now adapt again. None of this means that every transmission fluid change will cause a problem, just that too many transmissions have been brought in for repairs after a recent fluid change, and when prompted the owners acknowledged that the transmission was shifting fine until they changed the fluid. These cases are entirely separate from those that had a shifting problem, and new fluid didn't fix it (what I would call the faint-hope clause).

This is an interesting argument- although I'd need to know where the drain is- and if teh VB is drained, the TC, or what

Originally Posted by JCL

What is different from many years ago when transmission fluid changes were recommended by all manufacturers?
1) Fluids are far better. Synthetic or not, they have better additive packages that are more stable, and which thus last longer.
2) Transmission coolers, thermostatically controlled, are far more common. We used to put transmission coolers on vehicles that were towing, and some heavy duty applications had them standard, but they are now much more sophisticated.
3) Lock up torque converters have become commonplace, primarily for reasons of fuel economy. Heat is the biggest enemy of transmission fluid, and that heat comes largely from the torque converter. When it is in lock-up mode, there is no significant heat being produced. Long transmission life will be promoted by driving habits that keep the torque converter in lock-up mode, particularly when towing.
4) Electronic controls have become commonplace. Computer algorithms are managing the shifts, preventing shifts that would stress the clutches too much (ie high speed downshifts), and they are causing shifts to be much crisper (less clutch slip, less heat). In the old days, a "shift kit" simply firmed up the shifting via stronger springs or different check valves in the valve body, and that was a standard part of a performance upgrade or a towing package. It has gone one step further, in that engine management computers are integrated with transmission control computers. By backing off the timing when the shift happens, power is momentarily reduced, lessing the shock on the driveline. That is why those fullpower shifts are made so smoothly.

All of the above promotes longer fluid life. Will it last forever? Of course not.

How long? BMW says 'no time limit' or 100k.

Originally Posted by JCL

But will it degrade slowly enough such that something else will break before the fluid is unserviceable? That is what BMW is essentially saying. I agree with that, but based on my experience more than any blind faith in BMW maintenance recommendations.

There are members here with transmissions far beyond 100,000 miles, on the original fluid. What that really means is that other things haven't broken yet, and the fluid has just soldiered on.

If owners do want to change their transmission fluid, I think that is fine. I wouldn't, but that is just me. If owners do change it, I would use BMW recommended fluids (no aftermarket fluids), a new filter, and a very careful adherence to the BMW procedure for getting the correct amount of fluid in it, using a thermometer to determine fluid temperatures while setting the level.

Anyway, my quarter is up. Time for someone else to offer up counter opinions.

Thanks. Good discussion.

I am truly surprised at both the argument that a fluid change is a risk (afterall, BMW does recommend one, so how can it be a risk?), and the argument that ATF has virtually no life limit....

A

[JCL]

Originally Posted by ard

Did not see a 'cooler maintenance' in their schedule...nor do I think such a thing exists. Clean the fins??? that kind of "maintenance"?

Since heat is the enemy, maintaining the transmission cooling system is key. The thermostat could be replaced, the cooler and lines could be inspected. I wouldn't expect to see it in the BMW schedule, but you already have the schedule; you asked what type of maintenance would have the biggest impact in extending transmission life.

Originally Posted by ard

If you can show me ANY data that supports a "100,000 mile, unlimited years" lifetime on ANY ATF, you get a beer.

How about transmissions over 200,000 miles with the original fluid? Real world data? There are posts on this forum. Here are a couple that I came across quickly.

Originally Posted by a regular poster

2001, 118000 miles (189000 km). Still going strong. Not much problems and failures.... The original oil is still in the tranny...

Originally Posted by another regular poster

I have 115,000 miles and I have the original oil in the tranny as well. I have never heard of a transmission on a BMW X5 going out because of bad oil. .

If those tranmissions can go those distances on the original fluid, doesn't that suggest that the factory fill fluid can last just fine?

Originally Posted by ard

This is an interesting argument- although I'd need to know where the drain is- and if the valve body is drained, the TC, or what

I assumed draining the fluid through the pan, the valve body being drained when the filter is changed, and the torque converter not being touched.

Originally Posted by ard

How long (will the fluid last)? BMW says 'no time limit' or 100k.

Life of the transmission, whatever interval fate and non-fluid related failures cause that to be.

Originally Posted by ard

I am truly surprised at both the argument that a fluid change is a risk (afterall, BMW does recommend one, so how can it be a risk?), and the argument that ATF has virtually no life limit....

The entire point was that doing a transmission fluid change incurs a risk. If there was no risk, it would make complete sense to do it regularly, given that we agree that clean fluid is in general a good thing. It can be a risk whether or not BMW recommends doing it. Compare it to surgery; you can often repair a problem with surgery, but surgery is generally not without risks. It is a tradeoff of likely benefits versus potential downside. I also do think that ATF has a life limit, just that it is longer than the MTBF (mean time between failures) of BMW automatic transmissions. All this would change if we had posts about regular transmission failures involving burnt fluid or clutches, at mileages that correlated to having missed fluid changes.

Cheers

Jeff

[FSETH]

Originally Posted by JCL

My lack of support for changing the fluid is not because "BMW said" but rather because I see little benefit to changing it, and a small but real risk. The risk of damage is slight, but it exists. At the same time, I think that the transmission is likely to fail from non-fluid related causes prior to the fluid degrading to the point that it causes a transmission failure itself...

There are members here with transmissions far beyond 100,000 miles, on the original fluid. What that really means is that other things haven't broken yet, and the fluid has just soldiered on.

This entire post by JCL was great, IMO, but the above comments stood out the most to me. I appreciate you pointing out that fluid changes DO come with a small, but real risk. I think some people have a hard time believing that. What you say makes sense to me personally, but then I don't have any hard data to back it up. I take your word for it as someone who seems to have extensive knowledge and experience in this arena.

I also agree that there are simply way too many 100,000+ mile X5's rolling around out there that are on original transmissions and fluids for me to think that a breakdown in fluid is the main cause of BMW trans failures. For every person with over 100k miles on original fluid there is another who's trans failed under 50k miles. It seems as if the age of the fluid is inconsiquential to the life of the trans in most cases.

Quicksilver also made a good point that people are going to do what they want to do when it comes to this issue. At the end of the day, do what makes you happy. Just dont think that changing the fluid is going to prevent trans failure and realize that there is a small risk in doing so. It is not always that new fluid = better in an auto trans.

For what it is worth, I have an 02 4.4i with 109,000 on the original trans and fluid and it runs fine (knock on wood). I also have an e36 325i with 303,000 miles on the original automatic trans. I bought that car with 100,000 and have changed the fluid 3-4 times over the past 7 years or so. Started slipping a little between 2-3 gear about 60,000 miles ago, but it has been soldiering on.

I would be curious as to what the average lifespan for a BMW automatic transmission is these days anyway. I bet it isn't that much over 100k. BMW probably doesn't see any reason to recommend changing the fluid before that mark because they know that the original fluid will last the average trans lifespan anyway.

[JCL]

Originally Posted by FSETH

At the end of the day, do what makes you happy. Just dont think that changing the fluid is going to prevent trans failure and realize that there is a small risk in doing so. It is not always that new fluid = better in an auto trans.

I can fully support this. There are real benefits (of the 'feel good' variety) in working on a vehicle, and there is nothing wrong with doing some small project to increase the feel good factor. I change my own brakes and put my winter tires on, not because I can't afford to pay someone else, and not because my work is any better than another mechanic's, but simply because I like working on my vehicle and these are two of the few things left to do at home on a nearly new vehicle.

[ard]

Originally Posted by FSETH

T. I bet it isn't that much over 100k. BMW probably doesn't see any reason to recommend changing the fluid before that mark because they know that the original fluid will last the average trans lifespan anyway.

And my entire point is that fluid degradation is part of the cascade that leads to transmission failure- that in an internally lubricated mechanical/hydraulic assembly, the fluid must be considered a wear component.

I do not understand how one can say "The transmission failed at 150k, but it wasn't due to not changing the fluid for 10 years, the parts just wore out"

I wonder if the average lifespan would increase if we had an ATF change at say 40k intervals?

I believe it would increase.

Others here are convinced there is no benefit.

There is no 'right' answer, yet, according to my research. Anecdotes abound, supporting both sides. Plenty of inferences from manufacturers marketing info and 'recommendations', but no public data from which to draw conclusions. Undeniable historical data supports regular maintenance, but new advances in fluid and transmission design may support extended intervals. Perhaps the discussion is 'how extended'?

A

[FSETH]

Originally Posted by ard

I wonder if the average lifespan would increase if we had an ATF change at say 40k intervals?

I don't know. I wish we could prove that, but I don't think we can. It seems like there are way too many failures of low mileage transmissions for me to think the fluid is a real concern. To me, the people with over 150k on original auto transmissions (new fluid or original) are lucky because BMW automatic transmissions seem to be problematic from very low mileage. Even before 40k miles. I do see your point though, but how do we know if the same thing that failed on the low mileage trans is not the same reason that one failed at 125k? Regardless of fluid condition? Also, will the new fluids additional benefits (if any) be worth any risk of changing it?

I am no expert, but aren't most of the trans failures (low or high mileage) related to items not necessary affected by fluid, or atleast not due to worn fluid no longer capable of doing it's job?

Has anyone here who has experienced a trans failure for any reason had the transmission professionally analyzed? Would be interesting to see the results from a few failed transmissions with and without fluid changes.

[Lubehead]

I thought I should reply to ard's comments;

What does "well served" actually mean?

By that I mean to infer that the results of their (ZF's) recommendations do not create a negative perception of the company or its products.

Do you mean that ZF believes the longest service life will be achieved by not ever changing the fluid?

No, I did not say that and with the aforementioned 100k recommened change interval, evidently ZF does not either.

Or has this become a calculus of 'ownership costs' and 'owner hassle' and 'likelihood of trade in' combined with odds of failure to determine this is 'best'?

Isn't that suggesting a planned or expected failure rate? I cannot answer that but certainly don't subscribe to it.

I'd like to think ZF & BMW have ONLY the longevity of the AT assembly as their sole determinant as to the fluid service. Until that is confirmed, I thin the community is ill served by broad assertions that 'high tech' fluids will save the day.

To me it's the sum of the parts (the lubricant being a part) that allows the recommendations to be made. It isn't about a "high tech" fluid, rather it's about the total system design. No broad assertion regarding fluid quality.

In regards to my suggestion for an oil sample valve you asked;

Personally I suppose I agree, but I need to ask you "why?" Isn't the BMW interval of 100,000 miles satisfactory?

m5james post suggests that driver actions are a contributing factor to transmission and other component life. He also states that he adheres to routine transmission fluid changes as a matter of what he (and you and others believe) to be effective in providing longer transmission life. And while I do in fact agree, the difference I would suggest is that by having an oil sample valve, one could in fact determine the appropriate drain interval for a specific transmission driven by a specifc owner in a specific environment.

We always want to change good fluids as opposed to changing fluids that are deteriorated which as m5james states

there is absolutely NO fluid that doesn't degrade over time. Period.

The challenge is knowing when to change the fluid to achieve the elusive maximum transmission life goal. Without analysis, fluids may be changed prematurely, or perhaps, (I can only surmise) just before they dramatically degrade, assuming the 100k recommended change interval is in fact based on engineering or empirical evidence which suggests it is the most appropriate interval for the majority of applications.

And thanks to JCL for the Maintenance Management document.

Great thread!