I decided to start a new thread on this subject as I am looking for advise for the below transmission issue:
I recently got a 2007 MC base a little over a month ago with 122K miles. The transmission shifted great through all gears using D, DS and manual mode. There was no flares and no indication of slippage in any of the gears. About 3 weeks into it, I began noticing a slight "flare" occurring when it shifted from 3rd to 4th. I would compensate the shift by letting off the gas a little to allow it to shift into 4th. After 4th gear...5th and 6th were still fine. I started to only use DS mode as I was able to "feel" it go into 4th and better control it. I then proceeded to do my first fluid change (3 quarts came poring out right away as there was no overflow pipe installed). Of course the fluid was brown and appeared to be burnt? (the smell was about the same as the new stuff?). I checked for any metallic particles and found none. Slightly after this, I noticed that the shifting became worse from 3rd to 4th, as it appeared to be "slipping" more and going to higher Revs. Now, after a second fluid swap (getting close to flushing out the old), it is not even going into 4th. The engine light kicked on, which finally gave me a code of P0734 (Gear 4 incorrect Ratio) and of course, it landed in safe mode M4 or M3. I have been researching all the threads and video's out there to try and determine if it is the following:

1. Solenoid issue
2. Electrical related to the Solenoids
3. Valve body
4. and of course, the K2 clutch pack
5. ???

I am at a crossroads right now and don't know if sending it in to have a diagnostic is going to tell me anything without dropping the pan? I currently have an appointment set with AAMCO down the road to see what their "free diagnostic" can tell me. Most of the European shops are telling me they would just put in a new tranny with what I am describing to them over the phone

Any help on this would be greatly appreciative as I am going cross-eyed trying to figure this out, and of course want to limit the amount of money going into fixing as I have no problem going to pick and pull to get another low mileage and swapping it myself. Which then opens up another issue on what type of condition a "used" tranny would be?

 

You could start with the valve body. Check resistance of each solenoid. You could also take it out and feel the clutch packs behind it. Look up 09G transmission on you tube. There is a guy who takes apart and do VB tests...etc

you could also look for the manual online to check signal continuity. 09G is the key word.

 

I wouldn't take it to AAMCO.

 

Thanks for the suggestion on the VB as I have been asking this same question to multiple Transmission shops describing the same issue, and they all think it is something else?!? I will drop the pan for the first time this week to check for any contaminants at the bottom as well as dive into the VB to check the solenoids. The few videos on the tear down on the 09G are pretty informative as I will look to them for guidance. As far as AAMCO, I really had no intention of using them as they were close to me and wanted a "second" opinion at this point