I posted this topic before(12/03/05), but I only got one reply(12/04/05). So, here we go again. I have an 89 pickup w/ a 22RE(225,000 miles) and auto trans. A few months ago it just stopped shifting into overdrive. The fluids were new at the time and at the proper level. I changed the fluids and it still wouldn't shift into overdrive. No leaks or any visual problems. Then I had the trans replaced and still the same thing. What could be the problem? A sensor, faulty wires, vac. leak, torque converter? It's still strong from 1st to 3rd, just no overdrive. I've run out of ideas. Can anyone help me? :confused:

Typically, there are sensors that inhibit OD until the engine is warm, below certain speeds, etc. that could be bad.
Torque conv is a possibility.
Bad connection/broken wire to tranny (not getting L/U signal)
Bad solenoid in tranny.

You may need a competent tranny shop (hard to find), not one of the rip-off tranny chains.

The first thing to check is the overdrive switch itself. That and the wiring associated with is the most likely problem.

O/D soleniod was changed out with the old trans. I'll have to check all the wires then. If I can't find anything I'll just have to go to AAMCO. Thanks for the ideas guys.