I need help guys... I recently purchased a 4.8 Liter Vortec out of a 2003 Silverado 1500 with the computer and wiring harness. The only thing about this is that it was married to a 4L80E and I already have a 4L60E from a 2005 silverado for it. Now the wiring for the transmissions don't match up and I want to know if there is any way that I could use the harness with the 4L60E and if so will I need to reprogram the ECU. I mean the 60 came with the connection but all the wires are cut so can someone give me some advice here....

 

If you would have taken the time to look at the 5 or 6 threads at the top of the the page you would have seen your answer about the wiring.
And yes, you will need reprogramming.

Are you sure its a 4l80e? They never came from the factory with a 4.8...

 

They do in the Express and Savana vans. I've worked on and driven a few. Granted they were somewhat loaded but you put your foot down and they slowly start to roll ahead. No idea why GM made that combo. Then again they used to put the 4.3 liter in front of the 4L80E in some G vans.

 

Yea, I thought I had read that somewhere, but he said it came out of a silverado... That's the reason I mentioned it.

 

yes it is from a 4L80E but what about the two wire that I will loose and one that needs to be rerouted...