Okay, in the last couple weeks the truck has become a bit erradict with its shifting into OD.

Most times I could click the "OD OFF" button on and off and the truck would then shift up to OD and be done. But lately, it hasn't been doing the final shift.

The OD engagement seems a bit intermittent, and is beginning to favor not making that final shift from 3rd to 4th.

When I pulled the codes, it was throwing the code for "Part Throttle Lock Up Solenoid Shorted or Open".

Truck is a 1992 Dodge W-250 4x4 5.9L gas engine, 46Rh transmission.

So, what needs fixing and how hard is it?

try changing the torque convertor relay in the fuse box under the hood driverside. swap the t/c relay out with the horn or trailer relay. if the overdrive starts to work again get a new relay and put in the t/c slot and put the horn relay [the one you swapped out].if this doesn't work then the t/c solenoid is bad.

I was reading through my service manual the other night and one thing it mentioned that affected shifting was the Vehcile Speed Sensor. I was chatting with a friend who mentioned that Dodge's had a problem with the magnetic head in them attracts fine metal particles that are created as the transmission naturally wears with age.

Since the sensor is fairly easy to access, I'll pull it tomorrow and give it a clean.

Well, not certain what fixed, exactly. But I changed the TPS out under warranty (The voltage range was coming up correct when I checked it 1 volt at idle, 4 volts at WOT), the Vehicle Speed Sensor, and replaced the fluid and filter. If I was to guess, I'd say it was probably the fluid since from the looks of it the State of Oregon didn't service the transmission. It shifts smoother now, so hence my theory.