How many here have owners manual with contradicitionary information on AT service

[JCL]

Originally Posted by Doru

The transmission is not built by the car manufacturer. therefore, one should look up what the transmission manufacturer recommends. BMW has no say in this, owner's manual, or service manual.

Transmission life and wear rates will be significantly impacted by the trans cooling system and the integrated control strategy. The cooler works to warm the transmission on startup, reducing cold-start wear. Sufficient cooling in high ambients changes the point at which the transmission encounters severe service conditions. Backing off the engine timing during shifts reduces clutch wear, and heat. All of these are BMW features that you are ignoring compared to the same transmission installed in another manufacturer's vehicle. BMW has the most say in this, as we are discussing a system, not an isolated component

[JCL]

Originally Posted by trader4

Also, folks saying to listen to ZF obviously haven't listened to the ZF video that was posted.

Selective hearing, or confirmation bias. Take your pick.

[TiAgX5]

Originally Posted by trader4

Also, folks saying to listen to ZF obviously haven't listened to the ZF video that was posted. I quoted it in a post I made a couple back. ZF clearly says to adhere to the *vehicle manufacturers recommendations for fluid change interval*. That would be BMW. And that ZF fluid is designed to maintain it's characteristics for lifetime, per the vehicle manufacturers specifications. After that, ZF says if the vehicle is used in extreme conditions, then the fluid should be changed every 50 - 70K miles.

I posted the ZF video and listen fine.

Seeing as I regularly tow a 6k lb trailer in TX and FL heat and stop & go traffic, I consider it severe duty and choose to do fluid/filter swaps.

First change was at 100k miles (when the X was purchased and hitch was installed/severe tow duty started), will be doing 2nd change soon (185k miles).

If BMW and/or ZF were to state that LifeGuard fluid has shown NO significant loss in cooling and lubrication ability thru severe duty, with over 10 years of use, and over 150k miles, I would leave the factory fill/filter in place.

ALL lubricants & coolants become less effective and corrosive thru useage.

[JCL]

Originally Posted by TiAgX5

ALL lubricants & coolants become less effective and corrosive thru useage.

Irrelevant. It doesn't need to last forever. Just longer than the transmission, without impacting transmission life.

Oil never stops being slippery. And in this case, the lubrication demand is very low, such that a 10w hydraulic oil like ATF lubricates it fine. It is a sealed system, unlike engine oil, so not sure how it is becoming corrosive. The only fluid degradation that is happening that matters is to the additive package. That isn't impacting wear or heat conductivity, just shifting characteristics, and eventually oxidation.

[TiAgX5]

Originally Posted by JCL

Irrelevant. It doesn't need to last forever. Just longer than the transmission, without impacting transmission life.

Oil never stops being slippery. And in this case, the lubrication demand is very low, such that a 10w hydraulic oil like ATF lubricates it fine. It is a sealed system, unlike engine oil, so not sure how it is becoming corrosive. The only fluid degradation that is happening that matters is to the additive package. That isn't impacting wear or heat conductivity, just shifting characteristics, and eventually oxidation.

The trans is hardly a "sealed" system as you state.

There's a large vent tube near the valve cover, it vents directly to the atmosphere.

If BMW had installed a diaphragm seal box between the vent tube and trans, the system would have been "sealed".

These diaphragm seals to keep systems sealed have been used for decades on master cylinder brake fluid lids.

[Mike Gardner]

I have changed my fluid and filter 3 times. I have 213,000 miles and did my first change at around 100K (and each 50K thereafter. No problems so far.

[Quicksilver]

The OP said "Not trying to start a debate but a simple question:
My service booklet says to replace AT fluid at 100K miles, yet the
owners manual states it's lifetime. It's kind a funny."

Yet here it is again, 33 post later, another debate. I agree: It's kind a funny.
Maybe we should add a Transmission/ Motor oil forum.....

[JCL]

Originally Posted by trader4

The obvious problem is that BMW needs a clear statement on what exactly they mean by lifetime and they also need to be consistent. It's not a trivial issue. And if they have clarified it, no one has produced anything here to show it. Quite amazing for the Geman wunderking of cars.

I don't think it is a problem, really. People love to debate whether to change the fluid or not on boards like this, but there has never been a causal link established between extra fluid changes and extended transmission life. We don't see reports of transmission failures related to fluid condition. They fail for lots of other reasons (electrical harnesses, sensors, etc) but not usually fluid. That is what makes this trivial.

A parallel to this is the engine oil debate. BMW gave a very clear recommendation on engine oil and filter. But it didn't change that people love to debate doing early additional oil changes, and whether non-spec oil is better or worse.

The owner's manuals have never been revised, to my knowledge. Follow what is in your manual. Or your service booklet, which is generally published by the local BMW marketing organization, not BMW corporate. Or not. And just because a newer model of transmission has a different recommendation, doesn't change the recommendation that was originally given for a specific vehicle.

[bcredliner]

Originally Posted by JCL

I don't think it is a problem, really. People love to debate whether to change the fluid or not on boards like this, but there has never been a causal link established between extra fluid changes and extended transmission life. We don't see reports of transmission failures related to fluid condition. They fail for lots of other reasons (electrical harnesses, sensors, etc) but not usually fluid. That is what makes this trivial.

A parallel to this is the engine oil debate. BMW gave a very clear recommendation on engine oil and filter. But it didn't change that people love to debate doing early additional oil changes, and whether non-spec oil is better or worse.

The owner's manuals have never been revised, to my knowledge. Follow what is in your manual. Or your service booklet, which is generally published by the local BMW marketing organization, not BMW corporate. Or not. And just because a newer model of transmission has a different recommendation, doesn't change the recommendation that was originally given for a specific vehicle.

with one addition. In the BMW service manual it states some transmission problems can be corrected by changing the fluid. It does not state the problems that can be corrected. I take that to mean if you are having transmission problems a change of fluid could fix it.

[TiAgX5]

Originally Posted by bcredliner

with one addition. In the BMW service manual it states some transmission problems can be corrected by changing the fluid. It does not state the problems that can be corrected. I take that to mean if you are having transmission problems a change of fluid could fix it.

Good point Brian.

That statement means, in certain conditions, the fluid CAN degrade in a manner that can effect transmission performance.