My 1992 Es300 runs and shifts fine except today I was going up a big, long hill and after it downshifted out of overdrive, I was pulling the hill fine, then it started to slow down and then shifted into overdrive. I turned the overdrive off with the OD off button and it did the same thing coming back up the hill, it shifted into OD with the button on off. The hill is about 4 miles long and it was pulling just fine, kept the rpms about 3100-3200 at 55mph, it just all of the sudden started slowing down and then shifted up into OD. Any body have this issue happen.

 

check battery , charging and clean ground connectors, mine did this and i cleaned every ground i see, and checked the battery and charging.