I recently bought an '02 Winnebago EV camper with about 69k miles on it. Around 10k miles ago the transmission was rebuilt, including valve bodies, but the TCM was not replaced.
According to the previous owner, after the transmission replacement the van has had an intermittent problem where when climbing long grades (such as up to the local ski hill) the van will get stuck in gear and not upshift, instead revving very high. Stopping, switching off the engine and restarting fixes the issue.
I experienced this once myself in the couple of weeks since I go the van. Interestingly it will climb highway speed major passes no problem at all.
The previous owner had the van back to the shop that did the transmission rebuilt when he first saw this issue, but they could not find anything wrong. They suggested a new or reman. TCM module would likely fix it. Asking online, I was also recommended an external transmission cooler.
I had a mechanic check over the van before I bought it and the ECU was not holding any codes (I don't know how long codes stay in memory?). At present I don't have the ability to monitor codes or temperatures while driving, but will maybe buy an android phone, torque, and bluetooth OBDII reader if I can't figure this out.
Before dropping $1000 blindly on a new TCM is there anything else I can do, or any other likely causes? It doesn't seem like temperature if simply switching the engine off and on fixes the problem, as it wouldn't have time to cool down.
I wouldn't replace the TCM untill you've ruled out the numerous other more likely causes.
I think your transmission may be acting normal. When the trans heats up to a certain point when working hard (going up a long hill), it will drop down a gear and/or disengage the gear-lock to increase the engine speed and torque. In general, after climbing a hill and leveling off, it should eventually upshift. This is how my 1999 MV behaves when trailing our tent trailer.
Can you elaborate what speed and rpm you get when you have this problem? Which gear does it get stuck in?
Can you tell if it does a full down-shift or if it simply disengages the gear lock? If the gear lock is disengaged, the engine rpm will rev / increase if you give it some gas, whereas if the gear lock is engaged, it will not rev the engine. Possibly, the gear lock solinoid is bad.
It is also possible that the temp sensor on the valve body's electronic strip is malfunctioning. You can monitor the Transmission Temp using an VAG odb code reader to see what temp your transmission is running. It would help if you could monitor while you recreate the conditions where the problem occurs, going up a long steep grade.
Maybe the transmission plug contacts to the valve body need to be cleaned.
Do you know if both of your radiator fan motors are working? Occasionally a fuse goes bad or the resistor corrodes on one or both of them, which would cause inefficient engine cooling.
Some have suggested installing a more efficient transmission cooler to increase the life of the trans.
Certainly change the trans fluid and filter at least every 40k miles with VW Trans fluid as most in this forum have mentioned.
Thanks Bob, that's very helpful.
I've only experienced this once so far, but I was climbing the pass in "D", and I was only about a third of the way up the hill, so I wouldn't have expected everything to have got really hot yet.
There was a very harsh downshift (forgot to mention that), I think from 3rd to 2nd, then the transmission seemed to get stuck, I think in 2nd. As the grade eased off I accelerated but the van revved all the way to over 4000rpm, well beyond where it would normally have upshifted.
As the van drives normally most of the time I think I will just keep an eye on it for now and try to get the equipment to monitor the temperature and error codes before doing anything else.
I have an 02 with a exchanged trans from the dealer. if i'm in stop and go traffic for an extended amount of time it acts as you describe. I chalked it up to the trans running too hot. I bought a external trans cooler but have yet to install it. I had the Eurovan for two years and it has happened only twice