09 SS auto. Trans stopped shifting into 4th one day during my commute. No codes. Did battery lobotomy and it worked fine for the morning trip to work but on the way home lost 4th. Later that night in town I lost 3rd. Still no codes. Shifter knob is kinda loose, sometimes the button is stuck. Another lobotomy and I limped it to an AAMCO. scan tool gave no bad readings or codes and they drove it till monitors cleared. They don't think it's solenoids, want 4500 to rebuild. Haha. Any ideas here? I've read plenty of threads with similar issues but they all had codes.

 

I would not trust AAMCO to find their a-- with both hands.
The scan must be done while it is acting up. The fact that a lobotomy works makes me think there is a code of some sort. A bad solenoid should cause a code and more than 1 gear affected, like 1-3 2-4.
Does "until monitors cleared" mean "until all monitors have run"?
Any work done under the hood? Wires disturbed? Varnints?

 

Nothing amiss under the hood that jumps out. They drove it at least 18 miles while running the scanner. He said all signals are good monitors cleared during their test drives. No codes. I'm at a loss.

 

I don't know what "monitors cleared" means. If it means all tests ran, that is not possible as the EVAP test take up to 2 weeks to run. If it means they cleared the codes in memory then they erased any chance of diagnosis, the same as the lobotomy.

 

Guy said all the monitors ran

 

I would get a scanner and keep it in the car so you can check it whenever you want, maybe you'll find something that way.

 

Most scanners don’t read transmission codes. Seems to me to be a solenoid slowly dying. Not that hard to change if you’re handy. It’s been done on jackstands in a driveway .

 

My thoughts were solenoids as well. Of course the shops just want to rebuild it for the higher sales ticket.

 

The 4T45E transmits very common and parts are readily available , this how to from fastsuv shows the way to do it.

https://www.chevyhhr.net/forums/driv...olenoid-61313/

Very easy with patience and common sense.