A couple months ago I bought a 1993 D250 with an automatic transmission. After a couple weeks it started shifting in and out of overdrive driving down the highway. After doing some research I bypassed the TPS with a potentiometer. This did not fix the problem.

I ended up taking the truck to my local transmission shop where they said it was the overdrive solenoid. They replaced the solenoid and said I was good to go.

A couple days later when I got it out on the highway, it started shifting in and out of overdrive again. Back to the shop. They looked into it and said the overdrive solenoid had shorted out and needed replaced again. They looked over the transmission wiring harness and could not find anything that would have shorted it out.

Does anyone know where else I should look to find out what is shorting out the overdrive solenoid?

Thanks for your help.

-Andrew

 

check be hind the dash switch something rubbing or the switch it self there is a sharp steel guide member back there

 

You might want to by pass the temp sensor that is in the hot line. Mine did the same thing and it turned out the sensor was bad causing it to shift in and out. I tied the wire together and installed a new od solenoid and so far so good.