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2017 GMC denali HD diesel issues


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I have a 2017 GMC Denali 2500 HD with a 6.6 Duramax the truck drives like its in tow mode the entire time .You can press the tow button and it changes nothing ,Just adds the trans gauge . I thought it was just my truck . So I went to another dealer and test drove another 2017 GMC denali HD . it drove the same way . I bought my truck in 21-Dec-2016 ,After I drove off the lot I knew something didnt seem right . I had to go out of town for a week so when I got back, i took the truck back to the dealer to have the trans looked at . the response I got was that Gm done some changes with the sequencing on the transmission because there was tons of complaints on how the 2016 and down on how it drove when pulling loads . My truck drives like its in low gear and gears down hard when stopping with the metallic ticking noise . The transmission should free wheel when slowing unless your in tow mode and now its starting to go into high idle by its self . looked in the settings to see if the high idle was on and it was in the off position . I came from a ford diesel to GMC and now starting to feel like it was a mistake. I work off shore so soon as I get back home i am taking it back to the dealer again .My buddy has a 2016 GMC Denali HD just like mine and it shifts and drives normal I don't know anyone else has had this experience with the HD's.

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I have read other posts here where people have also discussed the various forms of transmission braking - it now happens in std as well as in tow haul mode. I also wonder if your exhaust brake is on and that is making a difference.

 

There is also a lot of traction control going on in the 17 over the 16 due to the fast torque ramp up of the engine.

 

I recently watched a video where the reviewer was mentioning the quick throttle response both on and off the throttle - he said it felt like the exhaust brake was being engaged.

 

My 07 gasser with the GM 6sp tranny also freewheels much less than previous rigs I have had. You can feel the transmission downshifting just by lifting the throttle and even more when you apply brakes - the down shifting is more aggressive in tow/haul mode. I know it is not apples to apples, but I think that GM is trying to get more transmission braking.

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My exaust break is off. My buddy has a 16 gmc denali hd just like mine and it drives totaly different than the 17 . When the dealer had my truck they put me in a 15 Silverado 2500 and it drove normal like all the other diesel trucks I have owned . I don't know what the deal is but I'm not a happy person at this point..thanks for the input . This is my first gmc so not a good impression for me on the performance . Love everything else about the truck

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Well I will be getting a new DMax in two weeks so I will have some first hand experience with it.

 

I know that my 07 gasser really does not change much in Tow/Haul other than stay in gear a bit longer - however with the new diesels and all that torque there may not be all that much for Tow/Haul to do esp in the lower gears.

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My exaust break is off. My buddy has a 16 gmc denali hd just like mine and it drives totaly different than the 17 . When the dealer had my truck they put me in a 15 Silverado 2500 and it drove normal like all the other diesel trucks I have owned . I don't know what the deal is but I'm not a happy person at this point..thanks for the input . This is my first gmc so not a good impression for me on the performance . Love everything else about the truck

 

Remember, your buddies '16 Dmax is not the same as your '17 Dmax. Lots of changes in the engine, and I would imagine, the tranny programming on the way it handles the torque. You said the other '17 drove the same way as yours, so is there really anything wrong?

 

Mark

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Drivetrain feels quite different from my 2011. Stays in a shorter gear and when you let of it really wants to slow down around town 30-45. If I go over 45 then slow down it stays in the taller gear. Not sure there is anything wrong with yours at this point but tough to tell over the internet haha.

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Im a gasser guy so i really dont have hands on experience, but I did read up in my 4 wheeler mag that there were a number of changes on the 2017 model specifically on the diesel engine and tranny combo. That actually was really the only changes made from 16' to 17' on these HD trucks. Maybe want to check it out was very informative but Chinese to me,,,lol

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My '16 will only tranny brake with the exhaust brake on. I will have to test drive a 2017 to see what the transmission sequence differences are.

Then you have something wrong.

 

My exhaust brake on, towing or not, in tow mode or not, works extremely well. At times I have to get on the gas because it is doing too much.

 

Mark

 

Sent from my SM-G930U using Tapatalk

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Then you have something wrong.

 

My exhaust brake on, towing or not, in tow mode or not, works extremely well. At times I have to get on the gas because it is doing too much.

 

Mark

 

Sent from my SM-G930U using Tapatalk

 

??? My exhaust brake does work well- regardless if its just the truck or if I'm pulling 12,000 lbs. Wasn't implying that it wasn't functional.

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