Bigmac

Maybe I can lend some info here on this issue. I’m an ex tech and for 25 years a factory field service rep ( not Gmc) so have been around the block. I had a 2017 6.2 8 speed and we replaced 2 converters and 3 flushes. Not to bad driving but pulling an rv was a dog ? peach seeds it shook so bad. It did settle down after 10 k miles but always there. Family member bought it so I purchased a 2018 identical truck Max tow 6.2 8 speed end of production vin thinking this was it and all the problems cured. Wrong. Same thing. IMO it is a tq modulation and the fluid breaks down. Instead of me getting upset I just lowered my expectations of a Gmc truck. Waiting for fluid fix and I don’t think you’ll get a rental as it is still drivable unpleasant as it is. You might be lucky especially if a good customer. I’m as anal as anyone on this problem ( ton of posts) but sitting back waiting to see if it really is repairable I understand the 2019 8 speeds do not have this condition but I believe a different converter is used. End of my rant ??

Coming from a 2017 6.2 max tow to a 2018 6.2 max tow ( end of production built) the trans shifting is much better. Haven’t had 1 bad shift yet in 4 k mikes. Seems it holds in gear longer when you let off the throttle and doesn’t upshift so quick. Drove the 17 the other day ( family member bought it) and it is night and day different. Still have t/q shudder on 2018? Oh yes especially when towing but is better in all other aspects. Waiting for tq upgrade as noted above before even addressing it.

My 2017 and 2018 6.2 max tow both did it when towing. 2015 5.3 did not get that high towing a smaller trailer. It goes to certain point then 2nd fan kicks on. All good.

Wondering how to install since there is no trans dipstick? Worth a try ??. Disconnect trans cooling return line on radiator or cooler I would think. Anybody figure it out?

Could you do the swap using a SLT grille instead of the Denali?

My friend - you have a bigger pair then I do for attempting this. Good luck and watching. Liking the direction you are going.

My type of shudder is In accelerating and will start in any gear especially with a load. Not to noticeable unless pulling a load. Same as last one so it’s “ normal” but not pleasant. It does not have the 45 mph rumble strip problem that many others exhibit. Drive up a hill and start applying throttle. It will shudder 1500 - 2000 rpms. Harder you acc the worse it will. Not real noticeable but like anything if you know it’s there you scratch it ??. End of the world - no but if your an old car guy with a bit of OCD you want stuff perfect.

I chased this shutter problem last year on my 2017 6.2 max tow till I was nuts. It will not go away and it got very bad when towing. It feels like t/q modulation. I changed fluid twice and installed a new t converter. Finally gave up as GM rep said normal. It did get better after driving 15k or so but will always be there. Had a chance to sell it ( long story) and buy a 2018 exact truck since the incentives where so good. Very little money difference $3k so made sense. I would have kept it as I got used to the chuggel as I call it. The 2018 does exactly the same thing but the trans shifting in the 2018 is night and day different. . Instead of shifting at a light load ( throttle) and banging into gear it will hold and shift smooth. I have read the tq has been changed in the 2019 and thinking the vibration issue might be one of the reasons. It is not bad except when towing and then it will shake very hard. Love the truck otherwise and that’s why I got another new one. I’m an ex tech and factory rep so I know the industry inside and out but lowered my expectations and live with its idiosyncrasies

I have had A 2017 8 speed max tow and now a 2018 8 speed max tow same truck. Long story sold the 17 to family member. Replaced 2 converters and several flushes. They both exhibited the exact same vibration as you described. Not bad unless your towing something. Then it really is severe. It is from the torque converter pulsing is how I would describe it. Get used to it as it won’t go away I noticed the 2019+ 8 speed is using a different converter. Hope they rectify as it is a great truck otherwise. On a positive note - the erratic trans shifting clunks are gone. Much better shifts but time will tell.

Keep us posted. Something I have wanted to do also.

My 2017 6.2 Max tow runs hotter towing then did my 2015 5.3 by a noticble margin but not alarming as it cools when the fans kick in.

I’d settle for the crappy shifting if I could get the shudder on accl out of it. 2 converters and 3 flushes and still apparent from 2 nd gear on very pronounced with rv towing. Still working with gmc on fix

Have had my tq replaced and new fluid and still shutters. Fluid change did help for short time but it has returned. Very bad pulling my trailer. So disappointed as the rest of the truck is outstanding. Purchased specially for towing. 2017 Max tow 6.2. Trying to decide my next route to resolve this situation.

Mine has the TQ shutter. Even after replacing converter it was still present. They did the multi flush with the newer fluid and it helped about 50%. Driving to see if it helps for the summer