6.2L 8-Speed Transmission

Fins · September 2, 2015

I read through some of the posts to this thread but not all ....

Here is my experience with a brand new 2015 GMC Denali 6.2 litre with the brand new 8 speed transmission

Within a very short while after driving my Denali with the new 8 speed transmission it was doing odd shifting that was random and very hard shifts . Even when cold starting in my garage I would hear a very loud metal to metal clunk without even engaging the transmission. While coming to intersections coasting and then proceeding "stepping on gas" it was like it couldn't decide which gear it should engage for which there was huge lag between shifts or sometimes just nothing . Pulling from a dead stop sometimes that truck would engage and then just stop "nothing there" coasting with the truck motor still running . Pulling from a dead stop on a hill to having nothing and rolling backwards almost hitting a car behind me while stepping on the gas . The other day I was sitting at a red light stepped on the gas "nothing" well needless to say the truck revved up to about 2500 - 3000 rpm and then decided to engage making the transmission huge clunk sounding like powertrain was being torture tested with squealing wheels . Sometimes while pulling up rush hour traffic going up hills between 50 kilometers per hour to 80 kilometers per hour the truck would surge between gears "not nice smooth shifting almost like something was holding the truck back .

Now the first 8 speed transmission was replaced with under 2500 kilometers took me 2 weeks to convince the service manager that there was something wrong . They were waiting for something to happen while they were in possession of the truck rather than going by my word . Finally it did for the service manager ...

Now the truck has 6900 kilometers and is needing another transmission so this will be on its third transmission for this truck now ..

Planning on going back to the 5.3 litre with the 6 speed transmission ..Hopefully this will work out with the change

redwngr · September 2, 2015

I read through some of the posts to this thread but not all ....

Here is my experience with a brand new 2015 GMC Denali 6.2 litre with the brand new 8 speed transmission

Within a very short while after driving my Denali with the new 8 speed transmission it was doing odd shifting that was random and very hard shifts . Even when cold starting in my garage I would hear a very loud metal to metal clunk without even engaging the transmission. While coming to intersections coasting and then proceeding "stepping on gas" it was like it couldn't decide which gear it should engage for which there was huge lag between shifts or sometimes just nothing . Pulling from a dead stop sometimes that truck would engage and then just stop "nothing there" coasting with the truck motor still running . Pulling from a dead stop on a hill to having nothing and rolling backwards almost hitting a car behind me while stepping on the gas . The other day I was sitting at a red light stepped on the gas "nothing" well needless to say the truck revved up to about 2500 - 3000 rpm and then decided to engage making the transmission huge clunk sounding like powertrain was being torture tested with squealing wheels . Sometimes while pulling up rush hour traffic going up hills between 50 kilometers per hour to 80 kilometers per hour the truck would surge between gears "not nice smooth shifting almost like something was holding the truck back .

Now the first 8 speed transmission was replaced with under 2500 kilometers took me 2 weeks to convince the service manager that there was something wrong . They were waiting for something to happen while they were in possession of the truck rather than going by my word . Finally it did for the service manager ...

Now the truck has 6900 kilometers and is needing another transmission so this will be on its third transmission for this truck now ..

Planning on going back to the 5.3 litre with the 6 speed transmission ..Hopefully this will work out with the change

You will need to look quick and snap up a 2014 or 15.

All 2016 1500 Denali's will be 8 speeds.

Fins · September 2, 2015

You will need to look quick and snap up a 2014 or 15.

All 2016 1500 Denali's will be 8 speeds.

I was told that the 5.3 litre comes with the 6 speed transmission and the 6.2 litre only comes with 8 speed transmission is this correct ???

Are they still building the 5.3 litre motor in the Denali ??

They do have two Denali's in stock with the 5.3 litre 6 speed transmission combination

redwngr · September 2, 2015

I was told that the 5.3 litre comes with the 6 speed transmission and the 6.2 litre only comes with 8 speed transmission is this correct ???

Are they still building the 5.3 litre motor in the Denali ??

They do have two Denali's in stock with the 5.3 litre 6 speed transmission combination

For 2015, 5.3's for come with the 6 speed and 6.2's with the 8 spd. The point I was trying to make is that if you want a 5.3/6 speed Denali, then you need to scoop up a 2015.

The 2016 1500 Denali will still be available with 5.3 or 6.2. -- but both get the M5U 8 speed.

The 2015 SLT 5.3 will get the 8 speed as well.

Fins · September 2, 2015

WOW then it looks like if I don't get a brand new 15 with the 6 speed I might be jumping into something totally different . After my experience with this new 8 speed transmission I'm totally done and will never drive another ..

bass mechanic · September 2, 2015

I can agree. I actually drove a 2015 6.2L 8 speed Denali on Friday. I was toying with the idea of trading up because I got a letter from my dealer saying they wanted to buy my truck. While the 2015 8 spd 6.2L 3.23 felt good. I didn't feel like it was THAT much better than my tuned 6 spd 2014 5.3L 3.42.

I really couldn't justify the cost of upgrading.

Hell, I wasn't even that impressed with the Magnetic Ride in the Denali. It was pretty good. Not outstanding like I had thought.

I did however also drive a 2015 2500HD with an Duramax and Alison. Also a Denali. And that truck rode phenomenal for being a 2500HD.

unless you drive the truck over a major dip you wont notice the MRS. but I can tell you for a fact the MRS made a major improvement in the ride quality.

before my 14 used to bounce pretty hard to the point I would get launched out of my seat. now it goes through the same dip without so much as a slight hiccup.

night and day and when towing it drives with a lot less osculation when I do go over bumps or dips.

as for the transmission I love the new trans yes I had some funny jerky shifts when coming to a stop but it's gotten better now and I am happy with it.

f8l vnm · September 2, 2015

Fins , your post scares me man. I'm in process of of having a buy back from gm and really though the 8 speed was better/drivability but this is bad stuff. Sorry about your troubles.

Like most said every V8 model for the 2016 + 1500's will come with the 8 speed.

The v6 is believe keeps same 6 speed

Would have been nice to see a 25 hp jump on the 5.3 as well.

Fins · September 3, 2015

Fins , your post scares me man. I'm in process of of having a buy back from gm and really though the 8 speed was better/drivability but this is bad stuff. Sorry about your troubles.

Like most said every V8 model for the 2016 + 1500's will come with the 8 speed.

The v6 is believe keeps same 6 speed

Would have been nice to see a 25 hp jump on the 5.3 as well.

So today I talked with the service manager and they had the truck for a few days to recreate the same issue that I was having . He tells me that it was easy to recreate unlike the previous transmission that's since been replaced . General Motors have been told about the issues with my truck transmission again , and the service manager were told they "General Motors" knew about issues with "bleed back from the torque converter" . Hopefully I used the proper term , and as explained it sounds like its losing transmission fluid pressure or something like that ?? Either way for this mechanical issue they figure its going to be atleast 3 months before they can send replacement remanufactured parts. They say its fine to drive like this ?? I cannot believe that they would say this is fine and safe to drive like this "scary" ...Couldn't imagine pulling out "merging" into highway traffic and your transmission decides to randomly quit .Its an accident looking for place to happen. And I asked the service manager about other 8 speed transmission this sounds like they will need this repair ..

I'm at a point right now I just want out of this truck not having anything to do with this 8 speed transmission anymore , I cannot trust this vehicle anymore breaking down where I'm fishing and have to hike out ...I found another 2015 Denali with the 5.3 litre 6 speed transmission just not the color I would like,and doesn't quite have all the same options as my current 2015 Denali ..

I did run that question about the 2016 models in the coming only with the 8 speed and none could comment or confirm this

Scout Abaco · September 3, 2015

Just wondering...why would you buy another GM after this one has been such a problem?

So today I talked with the service manager and they had the truck for a few days to recreate the same issue that I was having . He tells me that it was easy to recreate unlike the previous transmission that's since been replaced . General Motors have been told about the issues with my truck transmission again , and the service manager were told they "General Motors" knew about issues with "bleed back from the torque converter" . Hopefully I used the proper term , and as explained it sounds like its losing transmission fluid pressure or something like that ?? Either way for this mechanical issue they figure its going to be atleast 3 months before they can send replacement remanufactured parts. They say its fine to drive like this ?? I cannot believe that they would say this is fine and safe to drive like this "scary" ...Couldn't imagine pulling out "merging" into highway traffic and your transmission decides to randomly quit .Its an accident looking for place to happen. And I asked the service manager about other 8 speed transmission this sounds like they will need this repair ..

I'm at a point right now I just want out of this truck not having anything to do with this 8 speed transmission anymore , I cannot trust this vehicle anymore breaking down where I'm fishing and have to hike out ...I found another 2015 Denali with the 5.3 litre 6 speed transmission just not the color I would like,and doesn't quite have all the same options as my current 2015 Denali ..

I did run that question about the 2016 models in the coming only with the 8 speed and none could comment or confirm this

Fins · September 3, 2015

Just wondering...why would you buy another GM after this one has been such a problem?

Yes a lot of people would more than likely write off the experience and jump ship to another brand "thought about this for sure" ... I've had quite a few brand new GMC's for years without any huge issues , except for very minor recall issues trucks were very reliable ..

I'll update when or if anything changes in regards to the transmission issues

Otherwise if things work out I will be driving another 2015 Denali with the 5.3 litre 6 speed transmission combination ....

redwngr · September 7, 2015

Fins , your post scares me man. I'm in process of of having a buy back from gm and really though the 8 speed was better/drivability but this is bad stuff. Sorry about your troubles.

Like most said every V8 model for the 2016 + 1500's will come with the 8 speed.

The v6 is believe keeps same 6 speed

Would have been nice to see a 25 hp jump on the 5.3 as well.

For 2016, the 5.3's will come with both 6 speed and 8 speed, depending on trim level and/or options selected.

Ron.s · September 7, 2015

From GM website....

NEW! Transmission, 8-speed automatic, electronically controlled with overdrive and tow/haul mode. Includes Cruise Grade Braking and Powertrain Grade Braking Standard 1500 Denali And SLT

MYD Transmission, 6-speed automatic, heavy-duty, electronically controlled with overdrive and tow/haul mode. Includes Cruise Grade Braking and Powertrain Grade Braking

1 - Requires (L96) Vortec 6.0L V8 SFI engine or (LC8) 6.0L V8 SFI Gaseous engine. Not available 1500 Denali; standard 2500, 3500 Denali. Standard SLE and Sierra trims.

Same on Chevrolet...upper trims 8 speed, lower trims 6 speed.

BobHancock · September 8, 2015

Interesting and kinda scary discussion. I am planning to order a 2016 High Country 6.2 to replace my '14 5.3 which has been splendid. Giving me second thoughts but I was hoping the 6.2 would handle trailer towing duties easier.

f8l vnm · September 8, 2015

Prett stupid IMO to give higher trims the 8 speed and others still use 6 speed.

But this is gm

BobHancock · September 9, 2015

While waiting to be able to order a 2016 High Country with the 6.2L I asked them about these 8spd tranny's. Basically my dealer hasn't dealt with any of these issues, and confirmed the "adaptive" nature. Since I live in the mountains and drive in a spirited manner my truck has pretty much settled into hauling *ss. It rev's quickly and shifts smoothly and swiftly. I hope the new one adapts in a similar fashion. I like to feel the power as I'm sure many of you do. Better/easier towing is the bonus.

May I offer a remark kinda off topic, but I traded a 2013 Avalanche in for this 2014 High Country. The 2014 is pretty much a better truck all around. It's 600 lbs lighter, has more power, and pulls my trailer with aplomb. I'm expecting the 2016 HC with 6.2 to be an incremental improvement.