After the completion of a 4L60e to 4L80e transmission swap, it is still necessary to reprogram your ECU to recognize the new 4L80e transmission. One way to do this is with a Transmission Control Unit that you can find on Amazon. For the price of that unit, I opted to get HPTuners with a couple of credits and learn how to do it on my own. This way, I have what I need and I can do any future tuning I need to do, either by learning or by letting a Pro do it.
So, … programming a cars computer? That sounds very scary (and it can be) but HP Tuners makes it very easy with something called a Segment Swap. In the simplest terms, you find a stock tune for a 4L80e and you load just the transmission segment to your ECU.
The actual flashing of my ECU took a few seconds, and the hardest part was finding a compatible doner for the segment swap. I go into all the details in the video so check it out and see if doing your own segment swap is for you.