I think I've replaced nearly every necessary part on this truck minus the engine and transmission. I got code 17 after about 20 miles because the thermostat was not only stuck open, it was completely blown apart. When I replaced it, I had to remove it with needle nose one piece at a time, but it always shifted into overdrive.

 

these things come with overdrive?

 

today the tranny started shifting into OD, so I figure the solenoids on its way out. I guess thats the project for this weekend

 

Don't rule out the 2 wire coolant temp sensor. It could be stuck in the cold position making the computer think the motors not warming up. Therefore not letting od kick in. The dashboard guage is controlled by a separate sensor so the comp sensor could be bad without knowing