I don't really agree with your transmission fluid analysis.
It is not a given that a fluid replacement will cause a problem. It may do so. There are lots of examples of a fluid change causing a problem, but lots is a relative term. There are more examples of a fluid change not causing a problem. The real issue is whether there is any benefit to changing it other than the feel-good factor.
Any transmission fluid change (other than a power flush) is only going to change 50% or so of the fluid, because you can't drain the torque converter. The old fluid doesn't fill the gaps due to its thicker consistency, it is more that the new fluid contains fresh quantities of detergents that can loosen the deposits built up over time inside the transmission, allowing them to shift from where they were doing no harm, to somewhere that they do cause harm, like a valve body, with many small passages, or an actuator or solenoid.
Common wisdom is, if you are going to change it, to change it early and regularly so that there is no buildup inside the transmission. Also, common wisdom is to change the filter every time you change the fluid. Finally, common wisdom says to use approved fluids that meet the original spec. I agree with all of the above. However, wallyx5 didn't do any of the above, but had great results nonetheless. My point is that I don't think fluid has much to do with transmission failures, whether it is changed or not (unless you use a bad fluid that in and of itself causes a problem)
People are paranoid about X5 transmissions, and worry endlessly about them, but look at a few facts:
- Different models of X5 have either GM or ZF transmissions, and either 5 or 6 speeds (different models). Yet all have similar transmission issues. Why would all versions have problems if there was a weakness in the transmission design? Wouldn't one be better or worse? I suggest that it isn't due to the design.
- Some run for a very long time. That demonstrates that they are capable of running for a long time, without wearing out. I think this one is the longest on here, but there are others at high mileages as well.
- Transmissions have reported to have failed for a wide variety of reasons. It is because something broke in them more often than not. Breaking is not the same as wearing out. They are entirely different failure modes. Breaking can be a weakness in the metal; a failed solenoid, sensor, or controller; a failed actuator; failed wiring harness; or a software problem. Transmission used to fail years ago because the clutch plates were worn out, for example. Too much friction and heat. These aren't failing like that, they are simply breaking randomly, in many different ways, at a wide variety of mileages from 10,000 on up. There isn't a common failure time or mileage from the reports on here, they are spread all over.
- Given the above, it doesn't appear that there is much to be done to change the results of the transmission lottery. You can't change something which is random. It may fail. It may not. Abusing the transmission will speed it up, but not much else seems to matter.
If you want to change the transmission fluid, you should. If you don't want to, that is fine as well. There are arguments both ways. However, wallyx5's great results with his X5 have resulted in three posts about his transmission fluid practices. I think they are entirely irrelevant. He has shown that driven properly, the vehicle can run a long time, and that is great news. I just don't think it results in transmission fluid change recommendations.
