I have a 1997 k1500 that I recently bought and pulled the blown 5.7 out and put a 6.5 in. Used differentials, trans, transfer case, and engine from another truck and all the wiring. Swap went great and truck runs well, but for the first drive it has no speedo and is stuck in 1st. It can only go about 10-15mph if I had to guess and rpms just go up and no shifting. Seen a lot of threads so I tried replacing both speed sensors with no luck. There is a 2 pin flat connector on the trans and I’m not sure what sensor that is. The trans fluid is clean and full. It’s a certified Chevy rebuilt trans less than 10k miles ago and shifted great before the swap. All fuses are good but none in the cab or engine bay that say tcm or trans. Only code was for p0713 trans fluid temp sensor circuit. Reverse, park, and neutral all work fine. Shift into 1st, 2nd, 3rd, and drive and it doesn’t matter it stays in 1st gear. Not sure what direction to head from here. 4L80E trans. Thanks all for the replies.