I have a 1999 Trooper. Has 56K on it. I recently had a flush and fluid change on my tranny. The weather has gotten somewhat colder and it seems that my Troop is having trouble changing from 3-4. It wants to very slowly make that change and sometimes does not want to change at all revving my engine. I have heard that if my thermostat is stuck open that my tranny won't get to operating temp. I understand that and all but the operating temp gets up on the guage, so does that blow that theory? I haven't had it back in to check fluid level and all but plan to do so. Any thoughts or ideas? The problem seems to be more prominant when it is cold out, but I start the truck ahead of time and let it warm up, so that shouldn't be a problem. I dropped it off at a shop and they couldn't reproduce the problem, so I am stuck until I can prove it to them. Any help would be appreciated. Other than that, my Trooper has been great!