Do this:

Idle Adjust

 

I give a vote for TQ converter problems. It sounds like it is not unlocking when decelerating and that will kill the engine. Also, get that fluid changed and get a filter in there and make sure you have enough fluid. I know nothing about A/C systems because I stay far, far away from them, just another thing that can go wrong and I don't really need it. Hope you get it figured out.

 

If I read it right the truck drives fine and doesn't die with the A/c off so that would rule out the TC killing the truck. Unless there is some bit of logic that locks the torque converter when the A/C is on?(Highly doubt it)

I vote for an idle speed set too low.And when you pull the pan on the tranny check for metal filings and the like around the magnet. A little is normal if you find a lot it might be time for a rebuild.

However like Bad *** said. Start Simple.

 

When I bought my 12V as soon as Id throw it into reverse it would stall. Adjusting the idle is worth a shot and its FREE.

 

could the screens in the gov cause the late shifting we ran a diagnostic on it and had no trouble codes that would just leave the screens, filter etc. right?

 

Yes, But 89% of the time its TPS Related! What do you consider a late shift? How many miles are on the tranny?

 

^ brings up a good point. I'm not sure what the adjustment is for the TV cable(or whatever its called) is for these trucks. (I'm a stick man )

 

Turn ignition switch to OFF position.
Throttle Valve Cable Attachment
Disconnect cable end from attachment stud on control lever.
Verify that transmission throttle lever is in fully closed position. Then be sure lever on injector pump is at curb idle position.
Locate cable lock button. Button is part of cable retainer at engine end of cable.
Press cable lock button inward to release cable. Lock button only has to move about 2.0 mm (0.070 in.) to release cable in adjuster head.
Center cable end on attachment stud to within 1.0 mm (0.039 in.) and release lock button.
Check cable adjustment. Be sure transmission throttle lever and lever on injector pump, move simultaneously and as described in cable adjustment checking procedure.. Possible the cable stretched?

 

theres 148000 on it. its the original i bought it from the fert plant where i work and have records of all the matinence done to it. Fluid and filter never changed. Most the time to get it to shift i have to stab the throttle and catch it just right for every gear the only time it will shift properly on its own is when i bury the throttle from a dead stop. its like its not getting the right amount of press. it needs to shift. also its been this way for almost 3 years! I just recently bought it, but lasting that long with those problems makes me think it isnt burning the bands etc. if it was actually going out it would have by now right? I forgot to add it doesnt slip either

 

It's probably just getting to be time for a rebuild! 150k is pushing factory clutches and steels!