gabe-v

I need some ideas on what to look for. My 6l80 in my 09 Avalanche was acting up so before I did a full blown rebuild I figured I would try the sonnax zip kit. This is done and then I reinstall valve body, TCM, etc. and it won't even attempt to start. I notice the little "_" on the dash to indicate gear selection is not there. I drop pan check all plugs (un plug/re plug just in case).

I'm getting mixed results on searches as to replace whole TCM, replace the gear selection switch (little black thing on the side of the TCM) which I'm having trouble finding to try and swap out.

I know I have to relearn the transmission with my hptuners, but I believe it has to at least start to begin this process. I'm far from an expert tuner here so I'm not sure.

Anyway looking for some input as to what to look at next. I'm not having good luck searching and I'm just beating my head against the wall.

clinebarger

Make sure the Mode Switch is engaged in the Manual Valve....And make sure the Manual Valve is engaged into the Detent Lever.

The arrow is pointing to where all three come together.

gabe-v

Thank you. I will double check this!

wht/73

I had something similar happen to me with my t350 at the track!
The tiny S hook that connects the manual valve to the detent fell off at the line!
Needless to say I hit the revlimiter and pulled over thinking a blew it up!
Reverse was forward, no 2/3rd.
It would start however. ONLY because of the 8" treemaster.
Got it home through it on the lift dropped the pan and found the S hook and put it back and tweaked the part that retains it and PRESTO everything worked!
A month later I pulled it and put the converter trans combo in my sons malibu and he went a 12 flat with it on his 1st pass!
Sorry for the huge pictures!

gabe-v

Thank you!!! Missed the detent lever into the manual valve. Now i can fill'r up and see if the zip kit helped my issue.

wht/73

Good luck!