At 40-45 MPH it feels like the Torque converter is trying to lockup and really can't tell if it does or not . Feels like a surge forward, does it once and then OK for a while Car has been sitting for two days in VERY cold temps. Could it just be icing up somewhere or is the Tranmission ready to go ? Thanks

Since the transmission shifting and torque converter lock (cruise speeds) up are computer controlled you need to have a scanner hooked up that can read Transmission control module (TCM) fault codes. Also check for engine codes as this could be a misfire, but in that case the check engine light should be flashing while the engine is misfiring and set a fault code. If no codes of any kind are present in memory when the testing is done you almost certainly have a mechanical fault in the transmission like a malfunctioning torque converter clutch, but even that should set a fault code, so have the testing done.

check the transmission fluid.

ENGINE SURGING COULD BE WEAK FUEL PUMP, STOPPED UP FUEL FILTER,BAD TORQUE CONVERTER SOLENOID OR TORQUE CONVERTER. OR FAULTY TPS.

It should shift 4 times. 1-2, 2-3, 3-4 Then you will feel the torque converter clutch lock up which feels like a shift. The torque converter locks to increase gas mileage.

It is possible your lock up torque convertor has a bad connection or wire.
You should be getting a check engine light on in your dash.
You will need a OBD II reader plugged in to retrieve code.
Please let me know.

My Grand Prix did this too and it was old spark plug wires. Replaced them and no more **** that the tranny was messed up.

This sound like you are feeling the transmissions torque converter going in and out of lock up. When the torque converter goes into lock up it feels like a shift . One way to tell if it is the converter you are feeling is to push the od button disabling overdrive and see if it still does it. The converter will still go into lock up .

if the truck has a locking converter goin bad it will surge at steady speeds such as 55 mph the converter will lock and unlock causing you to feel an surging

Whats it do in neutral at stop?

you have an issue with the torque converter clutch, your symptoms indicate this is the issue, possible TCC solenoid problem or the torque converter itself has a shorted magnetic clutch.