Srode1

My '15 started shuddering again - about 10,000 miles after the dealer flushed and changed filter and fluid. It was fine up until a month or so ago, so took it in this morning. The dealer just sent an update, they are putting a new torque converter in it, looks like it will take them about a week to get the part and get it done, so I get to use a nice loaner truck in the mean time (not as nice as mine but it works).

I had shudder fixed by the dealer with a fluid flush and filter change - they were aware of the problem and that was the standard fix they were using and it seemed to work great until recently when I am starting to get a hint of it doing the same thing again. Could be road texture deceiving me, I will certainly wait till it get's more obvious. I have a 100,000 mile warranty since it's a 2015 and 2.5 years till the 5 years is up (bought a left over 2015 NHT Package truck with the 6.2) so I can afford to wait a while for it to get worse if it's going to. Love the truck otherwise, it still has an occasional clunky shift but its pretty rare and I can live with that - got a lot better with the fluid service for the shudder. The jury will be out for me on the new 10 speed for at least a year though to see if it does any better or has other annoying habits.

That's encouraging to hear - torque converter shudder showed up on mine a few weeks ago at 26,000 miles, and I just got it back from flush and filter change, refilled with 19353429 fluid. They said drive it 200 miles and if it doesn't fix it bring it back, its fixed right now but time will tell if it stays fixed. It does shift smoother but I haven't really put many miles on it - no reprogramming was done. Bulletin 16-NA-175 document 4526930 was listed on the paper work. I rode in an '18 Camaro 6 cylinder with a 6 speed transmission earlier this week and it had the same harsh 2/1 downshift at a stop a few times - so apparently that's not unique to the 8 speeds. The 2018 Silverado loaner I had while mine was in the shop shifted fine, but it has 130 miles on it and was the 5.3 6 speed so it was still learning for sure.

That doesn't mean something else won't lunch the tranny - things break, even transmissions that shift normally go out during the warranty period.

The warranty will mean something if you need the tranny rebuilt down the road.

There's nothing wrong with the 2017 LT Z71 5.3 6speed combo, it's a nice truck, but the total package on the 2015 LTZ NHT 6.2 8 speed is just nicer. The Z71 just rides like a truck compared to the LTZ NHT which rides like a car (surprisingly) and the 5.3 6speed combo feels sluggish compared to the 6.2 8speed. Towing (which is the primary reason I have the truck) performance would be less than I want I'm sure, and it's just not peppy. I would rather have an occasional abrupt shift than deal with being under powered vs what I want. The shifting on it is marginally better, I did feel some of the same harsh shifts just not as extreme as with the 8 speed, but the Z71 only has 3200 miles on it also so don't know if it will improve or get worse with time.

I have had a loaner 2017 Z71 5.3 6 speed 2 days while the dealer is doing service and a minor warranty fix and I can sure tell the power difference in casual driving between the 5.3 6 speed and the 6.2 8 speed. the 6 speed has a firmer shift that I expected compared to the 8 speed when it's behaving and the extra time in each gear is very noticeable when accelerating. Also surprised in the ride difference between the Z71 and my LTZ with the national tow package suspension, noticeably firmer in the Z71 (both crewcab short beds)

I did like the looks of the hood when I test drove a 16, and till think it looks nice. But wondered about the bird bath effect right off the bat. Hopefully nobody ends up with water spot damage on the paint from standing water. I ended up buying a left over '15 for a nice savings in part because I couldn't find a 16 with the options and color I wanted and I thought the longer drive train warranty was a nice bonus.

If you go to the end of the second page you can see the warranty labor time paid is actual time not book time so they get paid pretty well to do the work as including the test drive to make sure the rapid learn feature does what it is supposed to vs just relearning the old shifting that caused the problem to start with. Most dealer techs are on flat rate I would guess.

This is a good description of how it works and what can be done to correct specific shift problems. http://gm.oemdtc.com/492/transmission-adaptive-functions-and-correcting-low-mileage-harsh-shifts-2015-cadillac-chevrolet-gmc

I had mine in for the seat belt tensioner recall / reflash and they updated the TCM with the latest calibration and set it to rapid relearn when I mentioned the shifting problem (very helpful and I didn't buy the truck from them either). The harsh shift I was getting mostly cold was the 4 to 5 shift up and occasional down shift when slowing. The downshift slowing problem is gone completely, and the 4 to 5 upshift when cold harshness is much less frequent and less severe when it happens. It will probably take a few thousand miles for the relearn to work it's way through the process, but I'm cautiously optimistic for now.

The learning process on my '15 transmission has finally taken care of the the clunky shifting after about 2200 miles and 2 months of ownership. Shifting smooth as can be now. My only complaint is it took quite a while to get there. I decided I would let it go until about 3000 and if it hadn't 'learned' by then, I would take it in for an updated flash, glad I waited. I think maybe people are getting the reset to start learning again too quickly perhaps causing more problems than if they just let the system self adjust till its right.