JacobC1983

The Range Device has really calmed down my 6 speed transmission. I don't get nearly the surges and changes in pressure from the vehicle going in and out of V4 mode anymore. The lack of confusion has caused the transmission to shift less harshly because it always wanted to shift when it kicked back into V8 mode. One of the wierdest things for me was when I would be driving along, AFM would kick into V4 mode, and the RPM would raise to keep the same power, but I guess this would increase fuel economy. Now the truck is in transition less, which results in a better driving experience. The Range was worth every penny so far.

No problem.

I had this happen to me too. Go back to the navigation screen and fiddle with the bottom row of controls. Then go back to the Audio interface. I didn't have it happen again after that.

I have read that the later 2016s with the 8 speed get an updated transmission with the new torque converter and different valves. It seems that the later manufactured 8 speeds don't have as many issues, but they haven't been out as long, obviously. Your best chance would be a new transmission. They put the new torque converter in mine when I had it, and while it did clean up shifting, it didn't alleviate the large clunks and jolts forward when downshifting in parking lots. The worst part was coming to a stop at work in the parking garage when somebody jumps out in front of you... and the truck lunges forward towards them.

Honestly, I don't know how to help you but I can tell you what happened with mine. Most of it was through the dealer, I never called GM customer care once. My dealer called TAC (if that is how you spell it) multiple times trying to get mine taken care of for me. From several relearns to a new torque converter to them sending out a field service engineer, then finally to getting me GM trade assistance. I just called my service guy about once a week for several months giving him my updates on how my truck acted. I had the 6.2L with 8 speed (2015 model year) I never got mad at him, was always kind and he was more than willing to help me. Never threatened lawyers (and my wife is a lawyer, it would have been easy)... Finally I got to the point where I said I understand there is a problem and you can't fix something they won't let you fix or tell you how to fix, let's just get me into another truck with GM trade assistance - and they did. It took several weeks but it all worked out. My new 2016 6 speed drives perfectly after 1500 miles. I gave them my 2015 with 9000 miles, with the GM trade assistance I got a brand new 2016 with an MSRP within $200 of my old one, and it cost me $199. Well worth the trouble. The service manager and the sales manager both told me (in private) that the squeeky wheel gets the grease, just keep calling and good things will happen.

There is more than that in other threads on this site. I am glad most have good transmissions, though.

Just got my truck traded with GM assistance. I have to say, I am glad it's over. And can't believe it was an even trade. Traded a 2015 8 speed clunker for a 2016 6 speed (possible future clunker) and it cost me $201. The MSRPs were within $200 of each other pretty amazed how well GM and my dealer stepped up for me. Thompson Sales in Springfield MO is a great dealer!

Is your brand new denali shaking?

I am glad this worked for you, but mine started developing problems after 2000 miles.. Not before. Unfortunately a friend of mine with the 6.2 and 8 speed Sierra Denali didn't start having issues until after 10,000 miles. Strange how these transmissions act.

The field service engineer was completely wrong... I disabled grade braking and drove around in manual 7 and the truck still has clunking shifts. My service advisor is letting me know next week about the trade assistance and buyback options.

Thanks for the update. I figured as much.

I tried it on the way home but I only live a few miles from the dealer.. I will give it a shot on a longer drive this weekend. Let me know your results.

The field service engineer came back with a fix!!! He told me that all of my clunking and jerking of the transmission is actually caused by the active fuel management and I should drive around in manual 7 mode...... Needless to say I am pushing for trade assistance.

I just drove my loaner 2016 GMC Sierra SLT with the 5.3 and 6 speed for about 1000 miles and I think it shifts very good. With grade braking off it is perfect, but with it on is is substantially better than my 8 speed ever was.

This was one thing I always liked about my truck too. When my foot was in it, the thing was a delight... Nice smooth and quick shifts ... It's when my foot wasn't in it that caused the problems.

Ah dang.... the clunk on decel was one of the things I hoped a tune might fix.

What problems did it do before the tune, what did the tune fix, and what problems does it still have?

So nobody has hard downshifts that emanate through the entire drivetrain? Mine happen about once a week or once a tank of gas... There must have been something wrong with mine from the factory.

Thank you all for the comments. Good info in this thread.

Exactly.... If it wasn't for the transmission it would be one of my favorite vehicles.

Did you use tow/haul mode?

I loved that truck..... it was kind of gutless and I always wished I had bought one with the 6.0L when I could have.. but I really loved that truck. Everything about it. And it always rode smooth and soft on the highway on long trips.

At least this thread makes me think we are a minority of people. I hope my next one puts me in the "good" camp.

This my truck too.... It can be a real nightmare.

Lots of good information in this thread, thank you for the help. I feel as if I got a lemon and think I will still stick with the 6.2L and the 8 speed. The power of the 6.2L is intoxicating; especially compared to my last truck which was a 2009 Avalanche.