6.5 L no overdrive
 

Hello, I'm new to the site and diesels. I have a 1997 Chevy P30 step van with a 6.5 L and a 4L80e trans..The truck shifts through the first 3 gear great but it will only run 50mph and will not shift to OD. If I go down a hill and manage to reach 55mph the truck will shift to OD and stay there until I slow down and it downshifts. The engine also only runs about 160 degrees. I have not done anything to the truck, I just got it. Any ideas for things to look for. Thanks in advance!

Sounds pretty common, I recall seeing this a lot in the forums. Could be temp sensor causing both issues.

Some one has put a mechanical temp gauge in the truck and it also reads about 160 degrees. I was looking at the truck yesterday and found what I think is the idle stop solenoid laying loose on the engine. I found where it goes and bolted it on and took it for a drive and now it does not want to shift to any gear unless you lift the accelerator. Maybe just a coincidence this happened at the same time? The truck has a mechanical IP with a TPS for the tranny could this be a problem? If so what kind of voltage should the TPS show at idle and WOT? I also forgot to mention in my original post that this is a non turbo engine.

Today I changed the thermostat and that fixed my temp problem but still will not shift properly. If I press hard on the throttle it won't shift until I lift a little. If I ease on the throttle like normal driving it will shift normal up to 50mph then if flattens out. Either way I drive it will not run over 50 and will not shift to overdrive.