I have a '92 expo that won't shift into 3rd or function in reverse. Any ideas. Also, anyone have a diagram of the pressure ports (which one is for which clutch)

Sounds like you need a rebuild.

Before re-building try changing the tranny oil to the manuafures specs (make sure its right) and adding an additive like PowerUp NNL 660G. Without knowing the details you might just have stuck valve.

Good Luck.

Jim
NZ

My guess is front clutch. Smell the fluid, if it smells burnt, it's teardown time. You could have good pressure, but burnt plates. Or, you could have leaking clutch seals (that damaged the plates, and would have low pressure, but good valve assembly, so the pressure test might not tell you much.

Actually I did tear it down and saw nothing out of the ordinary...no burnt plates, no bad seals. I assumed it would be the front clutch also. Upon reassemble and installl with all new parts (rebuild) It operates the same. Valve body problem?

Seems unlikely, but you could disconnect the solinoid wire harness from the transmission. With no power to the solinoids, the trans should stay in third all the time (and have revese). Also, sometimes the reverse sun gear will disentigrate...