I know most of yall will say "just give up" or think im crazy to keep trying but this truck is my baby. I have a 2004 silverado z-71 with the 4.8. Trans went out 2 years ago. Had a buddy rebuild it for me, had all gears but it never shifted right. Bought a rebuilt one, only had 1st and 3rd. Bought a NEW one and again only has 1st and 3rd. Obviously now were thinking wiring problems. Can anybody point me in the right direction of where to start with the wiring. Since it now has a brand new trans it HAS to be electrical related right? Ive done all of the obvious stuff such as flushing the lines, cleaning all connectors on the trans blah blah blah blah blah. Somebody PLEASE help.

 

https://www.performancetrucks.net/fo...g-swap-413157/

check post #2. the main harness going to your trans may be messed up. pin out the wires to your PCM to make sure your trans is getting signal. also have you used a scanner to read your transmission codes on your truck? you may have codes and not throw a CEL.

 

I have not checked for codes. Can it be done with a regular scanner or is there a different one for trans? Ill see if I can find the complete pin out and start checking voltage. Somebody told me that if the rubber seal on the PCM is rotted it may get moisture in it and cause things to freak out. Is this true? Obviously it makes sense since water and electricity dont mix lol just trying to cover every little detail no matter how stupid it may sound. Thanks for the help.

 

you would need a shop scanner. something like a snap on modus or a tech 2.