Hello all! New member here. Was hoping someone could help! I have a 93 gmc 2500. I just dropped a vortec tbi 5.7l in. The truck had been sitting for close to 2 years waiting. Got it running, took it round the block, won't shift out of first. Speedometer works. Checked the iss and the oss, both are sending signals. Had a custom chip burned, so I replaced with the old one, still nothing. I hooked test lights to the solenoids, ecm is not sending signal to ground the a solenoid. Then I discovered this truck has a oss buffer. I have 12v coming in, a good ground. Have not checked signal going to ecm. Could the buffer have gone out and still send a signal to the speedometer? I did get several codes at first... 59, 85, and 86. The 85 and 86 haven't been set in a couple weeks, but I haven't driven far at all. The 59 is for Trans temp sensor voltage too high. Could this cause no shift? What could I be overlooking?