I've recently had my transmission rebuilt at 145,000 miles. They did the works; all new solenoids, torque converter, and even an upgraded shift kit(shifts rough, can even hear drivetrain slam when in between lights). I now have issues with less than a 1.5 years later(35,000 miles). I drive like a grandma, its a truck not a race car. I hardly tow anything.

I went on a trip right after the transmission was rebuilt and didn't feel confident about the rebuild. I heard a weird drone at 45-50 mph, even got the shop that rebuilt it to ride with me and they swore the noise was "spark knocking" On the rare occasion I have to floor it, the tranny will hold a gear and actually bounce the motor off the rev limiter.

Because of my Job, I've had to relocate to MN for a little while. About a month ago, my truck suddenly would not shift out of 2nd gear. I pulled off at a gas station to check the transmission fluid level and it was good. I pulled back out on the road and it shifted like it should. 2 weeks ago, I got the dreaded P1740 MIL code. Didn't think anything of it so I reset the computer, I lasted about 500 miles until the other morning. I thought because of how cold it was the truck wouldn't shift into OD(No P1740 MIL light yet). After an hour I needed to refuel by restarting the truck it shifted fine again. On the way home, I got the P1740 MIL light again and it locked me out of OD. I pulled off at a gas station to reset the computer and it shifted fine.

I've called the shop that rebuilt the tranny. Unfortunately, I am over their warranty policy by 4,000 miles. They are willing to diagnose the issue for free but I will have to pay for labor and parts. I can't get my truck back to them until Easter weekend. I am nervous I am chasing after a unicorn. What do you guys think it might be?

 

The 8pin plugs on the tranny are known to corroded because they get all the gunk from the road. It could be that, a bad sensor, or a bad solenoids. Here is what you could do. Unplug the 8pin connector on top of the trans right behind (towards rear) of the gear selector. I attached a picture of the plug and location. When you do this you will have no electronic functions (it will be like driving a manual) you will have to start out in 1st shift to 2nd when you want and then shift to D (which is 3rd) report back if it shifted.