Let's talk Transmission Maintenance...

[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....

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