When my trans is cold in winter on both 91 and 92 celica's I get on freeway and trans don't shift from 3rd to 4th for about a mile then it shifts I have 1.6L ST. IDEA"S Thanks Dale

you're not alone. my 91 toyota celica ST 1.6L does the same ****. and it's getting worse. i did some researching on the internet and found these articles of other celica owners with the same problem.

"1994 Toyota Celica mileage: 144,000. Hi, I have a 1990 Celica. This is my first Toyota and I have a weird problem. When the car is idling or slowly moving the temperature gauge works fine, then when it gets up to highway speed the gauge will slowly inch its way down to zero. When it registers in the cold area of the gauge the car will go out of overdrive and downshift to 3rd gear. In other words, as long as the temperature gauge is working overdrive works. Can anyone help with this problem? Was this a common ailment of the early '90s Celica's? Is this a big repair job?
Answer: Replace the thermostat in the cooling system. Yours is undoubtedly stuck open allowing the cooling system to go below normal operating temperature which causes the transmission to shift out of overdrive. This is not a common problem and it is not a big repair job."

"1991 Toyota Celica mileage: 90000. My Toyota has a problem during the winter months. After driving for sometime on the highway, the car will downshift from high gear and will not shift back to high gear. The temperature gauge also shows the car as being cold. This problem does not happen during the warmer months. I believe the problem has to do with the thermostat or some temperature related sensor.
Answer: The transmission will not shift into overdrive if the engine temperature is cold. Your problem is probably caused by a thermostat that opens at too low a temperature. Try installing a 195-degree thermostat."

heres an update on my celica that wouldnt shift into 4th gear in cold temps. After hearing that it was the thermostat, i went out and bought a new one from advance auto parts ( prices ranges from 4 to 10 dollars) and replaced it myself. it now shifts into 4th gear just fine and is as smooth as ever and it only took a couple hours of my time (if it werent so cold outside, it would probably only have taken an hour). it's a simple fix so dont pay someone to do it!

That's very nice to know...considering that I would have probably assumed that something was wrong with the trainee which we all know could cost major money.