Starts and runs great for having almost 260k miles. I have owned the truck for almost 19 years now. The transmission finally lost 3rd and 4th gear in 2017 and only drove it around the farm, manually from 1st to 2nd. Not above 30 mph. Recently had a rebuilt transmission installed along with torque converter. Ran good for a while but then started cutting out while going up gradual slopes. Then started to about Shake you out at idol. Got a #4 misfire, changed that plug and then the service engine light went off. Still ran bad so I changed all the plugs, plug wires. Thought I had fixed it until it completely warmed up. Now it wants to stall when put into gear. I have to be ready to gas it to keep it from dieing. Runs great after that until you come to a stop in gear. Any help would be greatly appreciated. No codes currently (been driving a few days for about 200 miles total) cleaned throttle body, idle air intake, maf, new fuel filter. New thermostat. I/m readiness shows 6 of 8 ok. Cat and evap or something like that are incomplete thus far.

 

Check the fuel pressure and the operation & integrity of the fuel pressure regulator.

 

hooked up the pressure gauge when the truck was warmed up and stalling. Gauge read 52 when I turned the key. After starting, the gauge went to 48 and held there after I shut the truck off.

 

Well, the factory spec for the fuel pump pressure is 55 - 62 PSI. You mentioned that you have replaced the fuel pump twice. What brand(s) of fuel pump did you use and how long did each last (time and mileage if possible)?

If you did not use either an ACDelco or a Delphi fuel pump, you could be looking at another defective fuel pump.