so i have searched and searched and the only thing i can find is info on the LML hard 6 to 5 down shift and a GMs update to fix it.

from all of the descriptions of the problem it sure seems like i am suffering from the same issue except it is on my LMM. the update appears to only apply to the LML.

AND... my issue only started shortly after getting stuck in some mud and rocking the truck back and forth to get it out. i shifted between 1st and R until i got enough grip and momentum to get out. then a few days later i noticed the 6th to 5th down shift starting to bang.

i have tried resetting the TAPs and it smooths out the shift and it seems fine but then a few days later it starts to bang into gear. a little at first then more harshly as time goes on.

From reading into the issue and what the LML update is supposed to do to fix, it is lowering the on coming clutch pressure on the 6-5 down shift. so tried playing around with the {D5188 to D5191} cells, dropping them a little at a time and resetting the TAPs. it seems to help but in the end it always seems to come back to the hard down shift.

as a last resort / test i tried disabling the 6th to 5th Kickdown Adaptive Learn Enable {D5056} and resetting the TAPs again. i thought that since it always seems to shift nice and smooth after resetting the TAPs and it seems to adapt itself to the hard shift then preventing it from adapting may keep it nice smooth. i know this is not the best thing to do but i was getting desperate and tired of whiplash.

anyways, it still adapted back to the hard downshift. so now i am looking for answers on the forums.

do any of you think i may have burned a clutch pack or two when rocking the truck back and forth using 1st and reverse? maybe the C3 as it seems to be used in R and 5th?

i didn't limp the transmission or at least it didn't throw any CELs or codes at me. i also recently towed 14K-ish lbs from Sacramento to Reno on the I80 (up hill most of the way) and stayed in 5th most of the time and it seems to not skip a beat.


what do you guys think. getting close to needing my built transmission now or is there other programming changes i should try?

thanks, Jason