Transmission issues

I don’t think you will have to. You have done all the right things so far, but have you reconnected all the electronic lines correctly. If reverse just one of them when you are wiring things back up and say go white to green instead of green to white, you will have a Silverado that won’t move at all. It’s just that simple.

And while it is just that simple, it is a lot more complex, too. The reason again is electronic. Have you checked to make sure the sensors are also installed correctly. It is all too easy to turn a sensor over and put it 180-degrees out of phase. In other words, it’s not going to work. What sensors might be involved in this? To name a few, there’s the throttle positioning sensor; the manifold air pressure sensor; the mass airflow sensor and then there’s also the solenoid pack. If it isn’t energizing correctly (it has put in backwards), then your pickup won’t move now matter what gear you drop it into.

The thing about electronics is this: while the functions it controls are simple in concept, their actual interactions are complex and just finding where a wire might be chafing and shorting or open is a long process that involves testing segment after segment of a circuit.

I’d pickup the electronics service manual and take a close look at the sensors used, the control modules used (they have their impact, too) and then walk through a circuit to see just what it would take to troubleshoot. Or, you can go to a service area that has a network analyzer (no not internet), a device that shoots a voltage down a wire and waits for a return. If there is no return, it can figure out from the time-travel figures where the device or wire may be going down. All either you have to do or the tech at the service area has to do now, is go through the miles of wire to find the specific problem and then rewire things appropriately. I hope this helps. Let me know what happens.