[crow]

Driving down the hiway about 80 MPH in over drive 93 automatic when the transmission checks out of overdrive. RPMs jump up and here I am winding it up down the hiway at 80 MPH in drive. I looked down to see if I had bumped the shifter and nope! What happened? I tried everything I could think of. Shifting made no difference. it would drop to second and down to 1st. reverse works fine overdrive just changed to 3rd gear???

[dakine858]

Originally Posted by crow

Driving down the hiway about 80 MPH in over drive 93 automatic when the transmission checks out of overdrive. RPMs jump up and here I am winding it up down the hiway at 80 MPH in drive. I looked down to see if I had bumped the shifter and nope! What happened? I tried everything I could think of. Shifting made no difference. it would drop to second and down to 1st. reverse works fine overdrive just changed to 3rd gear???

Well it could be a few different things, low fluid level, vacuum linkage control failure, internal clutch or band failure, broken vacuum lines. Start with a fluid change.

[artistang]

Since it is downshifting instead of slipping in 4th gear, I would check the kickdown system for damage. It could also be a main control pressure problem or governor damaged, worn or dirty. But.....by all means, check fluid level. If the fluid is not a pretty red, change it and the filter first.