1/2 ton silverado.. check engine light is on and tranny won't shift down from 3rd gear. So starts out in 3rd. diagnostics say there is low voltage readings in the torque clutch converter solonoid, and the 2nd to 3rd shift solonoids. Had it in and ran tests.. couldnt figure it out so they replaced the solonoids. It ran fine for two weeks and now is back to starting out in 3rd. Same problem. Any ideas out there???

 

There was an electrical problem that affected multiple solenoids. The shop couldn't figure it out so they replaced the solenoids, probably without testing them, thereby spending your money. I'd say find a new shop.

 

So I've been driving it and one morning it shifts fine and that afternoon it doesnt shift and then the next morning it doesnt shift and that afternoon it shifts fine again...this happens day in day out just started getting warmer out and all of a sudden my check engine light isnt on and it is running and shifting fine...i ran diagnostics thru on-star and they said there are no codes coming back said everything shows up as working fine???? Im really confused on whats going on

 

Hoffman Zac, unfortunately the lights or codes would have to be set for the dealership to be able to properly diagnose the vehicle. You could also check to see if one of the mechanics would be willing to take a ride with you while you attempt to get the issues to present themselves. Either way would be the best to get the vehicle properly diagnosed. I hope that helps and if not feel free to contact me back.

Jeff Morris, Chevrolet Customer Service