I just recently bought a 2005 Chevy Silverado 1500. (I hope I won’t get in trouble considering it’s not a Camaro or firebird) it’s a 4x4 and has the 4l60e. The guy I bought it off of said the transmission had been rebuilt, but after rebuild it would take off and stay only in 3rd gear when put in the drive or overdrive position on the gear shifter. I can manually shift it but it only has 2nd and 3rd gear. No overdrive or 1st gear. It also doesn’t downshift on its own either. And when I do manually shift it it shifts pretty hard. Definitely not normal. From what I’ve read so far, and from pulling codes, it has a bad shift solenoid A. I was considering just replacing all the shift solenoids while I’m in there, along with a filter and fluid change. Looking for any guidance here because I’ve never done transmission work before. Thanks for the read

 

Sounds like the shift solenoids aren't getting any power; if that's the case it could be a lot of things, none of them particularly difficult to fix.

 

where should I start?

 

First verify power to pin E in harness, Then If good adress codes . It would be helpful to know what actual code numbers you are getting.

 

I will figure out how to test for power. I will list codes here:
P0785
P0449
P0300
P0131