strange auto transmission, i'm confused Options

[95STHATCH]

I have a 93 st celica which has the 1.6 engine and an automatic transmission. Now here's my problem. I can be driving along and everything will be fine but all of the sudden it feels as if overdrive went out. At the exact moment it feels like overdrive went out the temp gauge will shoot down to cold. When it happens it only last for about 40 or 50 seconds. I am completely confused. My only thought is that maybe the temp sensor has gone bad and it is throwing the ecu off. Even that really doesn't make any sense. Please help me out. I thought I would check with you guys first to see if you all have any ideas.

[GeEkBoY]

OK, I know what is causing the problem. You are correct about the temp sensor. In a auto slushbox, there is a torque converter lock-up. Your tranny does not have OD as such, but what you are referring to is the torque converter locking up. It does feel like another gear. When the car gets up to a certain speed and the engine load drops below a threshold the converter will lock up, but only if the temperature has risen above a minimum threshold. The computer controls the lockup and with your wonky temperature readings, the computer is disengaging the lockup and your revs will increase. Fix the temp sensor problem and that will fix your tranny.