Transmission slow to leave low gears when hot

[fredikium]

Our 2001 Eurovan developed a new concerning problem on the hill heading east out of Zion NP.

At a slow point on the incline, it abruptly shifted into 1st gear - running 4,000 RPM at 20 mph. Even as we crested the hill, it wouldn't shift up as I would expect, despite my foot just feathering the gas. Eventually, if I completely released the gas pedal for 3-4 seconds, then slowly reapplied, it would shift. Did a similar thing a few times, at different speeds - got "stuck" in 3rd once as well on a lesser incline, with a similar solution once we got to a flat.

Visited a mechanic today in Flagstaff who had a few initial thoughts. He reset the codes and reprogrammed the basic TCM set points to make sure that wasn't the issue. His suggestion was to drive down to Sedona and back (downhill there, and uphill back) to see how it behaved.

All worked normal and as expected going there, but coming back, about halfway up the hill, it started misbehaving again. Tried stopping, turning it off and on, and restarting - no change - still in 1st. Tried using the manual downshift (3, 2), to see if it was a programming thing - no change - still in 1st.

What DID work was to stop, turn it off for 15 minutes in shade, then restart, and all was normal back to Flagstaff.

So it seems to be heat related - once the transmission gets over a certain temp, it starts getting "stuck" in lower gears and not wanting to shift up normally. Letting it cool off for a bit corrected the symptoms.

This EV got a rebuilt transmission about 40,000 miles ago. Is it possible it just needs a service? Fluid dump and refill? Or is it something more serious?

[joeintern]

I have 1999 Eurovan EVC

I had the same issue. I had heard so much about transmissions entering "limp mode" that I stopped immediately and camped until the next day, returning home down the pass. I am almost certain that my transmission fluid temps were way too high - so installed an external transmission cooler - and a Bluetooth obdii reader and torque pro app on my phone to monitor trans fluid temps. Others use scanguage to monitor. I highly recommend the external cooler as the original uses engine coolant to cool the transmission fluid. This makes little sense as the engine coolant runs 180-200+ On my trip post external cooler, trans fluid temps were 139-179...

I'm also going to change my trans fluid every 10-15k miles... as it is not that hard to do.

This is a good start for more info as Rialtas use the same engine/trans:

http://www.rialtainfo.com/vw/transmission.htm#cooler

[fredikium]

Thanks for the tip on the App and Bluetooth reader! I have a cheap plug-in one, but it doesn't give me any transmission info. At $20, plus $5 for the app, I'll definitely get the Bluetooth one and see how much more info I get.

I posted this same message on FB forum, and many recommended transmission servicing. I did take it in for that, and the mechanic said the transmission seemed to be in okay shape - no burnt fluid, a bit of metal on the pan magnet, but not enough to be too concerned. He did note our filter had fallen loose, so it wasn't doing much, and may have been affecting fluid flow. He cleaned it all up and sent us on our way, with the thought that our valve body may have been gummed up a bit by the filter having come loose.

Problem has recurred once since, on a particularly hot stretch in some up and down hills in Florida, but otherwise has been great. Will definitely be ordering the external cooler and installing ASAP, and will keep an eye on the operations to see if the valves have been messed up somehow.

[Abscate]

Running your transoil at 200-225 F coolant temperature will give you 50,000 mile plus life. Your trans was probably designed to run with the ATF at this temp and viscosity. The primary benefit of the external coolers is a high profit margin suck out of your wallet for an added Rube Goldberg of hose clamps, fittings, hoses ...all ATF leak points.
_________________
.ssS!

[jjvincent]

[fredikium]

I bought the BAFX dongle and the Torque Pro app as suggested above and found my transmission is running at 280°F, not the 220-225°F that is indicated above as normal.

Coolant temperature at that time is 210°F, and I wonder how much heat transfer the coolant can take at that temperature when it is also removing heat from the engine.

I cannot offer hard data to dispute the cash grab suggestion above, but I have read in dozens of different forums and VW sites anecdotal reviews that say their vans run better after installing the aux cooler. I have also been told by no less than 6 reputable VW mechanics that I should get one. Given the temps I'm seeing right now, maybe in my case it would get my temperature down to the normal range of 200-225?

I would add, the transmission was JUST serviced, and ATF is at the correct level.

[/b]

[Stripped66]

[fredikium]

Thanks for the input! I am an engineer, so fully appreciate the detailed troubleshooting approach you are suggesting.

First off, the app is reporting °C, and I am converting them to °F for the audience (I am Canadian and speak celcius, but recognize most here will appreciate the conversion).

The 280°F that I posted about yesterday was in a city, stop and go traffic, 95-100°F ambient (driving through Florida) - air intake reporting a bit higher at 110°F - and the transmission started misbehaving. After a 15 minute stop and shutdown/cooldown in a parking lot, all behaved normally again.

While cruising on the interstate at 65 mph, checked the reading and it showed 270 °F - no misbehaving, but also a relatively level road not requiring shifting.

More data gathered today...

Started up in the [hot!] afternoon and drove about 10 miles, small town driving (not repetitive stop and go, but a few traffic lights). Checked the temp at Home Depot, and it showed 200°F.

Carried on our journey north - after an hour on the interstate, cruising at 65 mph, transmission was running relatively level at 270°F.

So the sensor is not "stuck", but whether it is accurate is a fair question that needs to be confirmed. I don't have an IR gun handy, but can see how easy I can procure or borrow one.

Is VAG-COM something that is available to the general public, or is that just a VW tech tool?

[Stripped66]