the electronic valve body is the problem real common problem the all
do it and they are not cheap to replace

Buster wrote:"My Daughter's 1994 Caravan will not shift into overdrive.
The Tranny was rebuilt a couple of months before she bought it. The
motor does reach normal operating temp. What can be the cause?
Buster"

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 How many miles are on the vehicle, which engine?
 Was it a reputable shop that rebuilt it?  There are many upgrades
required to be installed into these during a rebuild, including the
controller.
 I had all kinds of problems with a 604 when they failed to replace the
controller -- which had undergone at least two upgrades.
 In other words, when I finally took it to a reputable shop, they
mentioned that this 'rebuilt transmission' was still using the  first
generation controller, where by that time it should be the third -- so
naturally the unit was not compatible with the upgrades hardware
included in the rebuild kit, and wouldn't control it properly.
 I'm not saying there's a high probability that's the problem with
yours, just that there are a LOT of upgrades on those, both inside and
out.
 Are you sure it's not shifting into overdrive, or if it's the torque
converter lockup not working?

I have one with a similar problem. It seems to overrev in each gear, and doesn't
shift into overdrive. If I drive a few miles, then shut it off and restart it a
minute later, everything works great. One time on the freeway, it went into
neutral - engine just reved up until I let off the gas. Coasted down to 40-45,
then it started working again, but with the no-overdrive, overrevving problem
until I turned it off/on again.

The previous owner had the overdrive solonoid replaced, with no improvement. A
dirfferent shop removed the computer to try a substitute one, and claimed the
problem went away, and stayed away after re-installing the origional one. I
bought it, and the problem came back a few days later.

Could this be a speed sensor or temperature sensor problem? Any other ideas.