Tilldain

Got my Truck back yesterday, after they called GMC back east they where feeling something different than i was and they wanted to check on it. They ended up performing the flush and fill procedure. so far after the initial drive home and back to work today. i have not felt the shudder at all at the highway speeds. he did mention that GM is putting out a new revised fix that should be available in the first quarter. for now im happy with the results. will report back if anything changes.

I have not tried the tow mode other than to check the temp on the transmission. Seems interesting that the ambient temperature could impact the internal system of how the tranny functions. Still don't have a call back from them I'll let you know what I hear and continue to test once the temps come back up Sent from my Pixel 3 XL using Tapatalk

Another Shaker/shudder/chugger. i bought my truck mid December. 2018 Denali 1500 with the 6. /w 21 miles has right around 1700 on it when i dropped it off at the dealer this morning. started noticing a small shudder while cruising home with the cruise set at 65 right around 1k miles. started doing my research on here and found this thread started reading up on the issue. it got really bad last weekend after driving for a hour or so on the freeway did not tell the wife about the issue and it was bad enough for her to notice from the passenger seat. my issue mirrored the TSB all the way down. Tack jumping around 1500-1600ish, not dropping into V4. cruising at 65. noticed it mostly on slight upward elevation changes where the little bit of throttle input was needed to maintain speed. Now this is where it starts to get more interesting. i setup my appointment for today. trying to duplicate the issue on Monday morning it wont do it i tried all the testing listed in the TSB locking it in L7 and it just wont do it. the only changes are it was colder than normal out here in the PNW 31ish in the morning. it never had the vibration once on my 15 mile commute Monday, Tuesday in either direction of travel. This has been something i was able to duplicate consistently up till Monday. Tried again this morning not able to duplicate it got a little shaky after it dropped into V4 mode but from what i read that is for some reason operating as intended per GM Engineers. i dropped it off at the dealer mentioned the TSB and let them take a look. no word back as of yet i will update as soon as i hear something. Thanks for all of the fantastic information and help you have all provided.