My own 8 speed problems & resolution

[MD11G200]

looks like this thread is dying somewhat are people not experiencing the problems anymore or just getting another vehicle, I'm approaching 36K and the short hop around town trips are still plagued horribility with hard clunky downshifts that push the truck forward while approaching stop signs 1/2 the time other times operates normal

[AgDoctor]

My wife's 17 Yukon Denali was experiencing some shutter last week while we were on vacation in the mountains. Seems to do it at around 30-35 mph. The truck has 21,000 miles and the 6.2/8 spd combo.

I haven't taken it in to the dealer yet but I plan to. My 16 8 speed got traded at less than 8,000 miles due to this issue. I also have a 17 Sierra AT with the 6.2 and 8 speed. I would be lying if I said GM has me a concerned.

At this point if they haven't found a decent resolution for the 8 speed they are not likey to, and since GM is abandoning the trans for the 10 spd why no option to upgrade to the 10 spd rather than so many shop visits?

I don't see me buying more GM vehicles in the future. Pretty lousy for all that have had issues and continue to wait for a resolution. Trying to do a lemon law case is not fun, as I had a 13 Tahoe that went to the shop on a wrecker 6 times before it was 6 months old. GM did nothing but my dealer helped considerably.


Sent via Morse code

[YukonXL04]

Hmm. Mine had the random cold start shift delay from 1st to 2nd. Might do it 1 time in 2 weeks, might do it 4 times a week. Other than that I love it. Truck runs and drives excellent with that 1 small exception. Taking it to the dealer next week for free oil change, I wonder if I should have them do the Mobil 1 fluid TSB while its there... 

[Jdub289f]

Wondering if anybody has had any more recent luck with the clunks and delays? For me it's during a slow to complete stop when I get back on the throttle, no matter how lightly I apply it. Happens almost every time I accelerate. Mine is a 2018 Sierra 1500 SLT E-assist. Kinda wondering if the e-assist crap has something to do with it too. I never had the shuddering issue at higher speeds, but they flushed with the new Mobil-1 fluid as well a few months back. I have never received any replacement of the torque converter, servo motor or valve body like some people have. I have about 12k miles now. I just want it to drive like a normal damn truck! Since they are lagging at coming out with a new tune, I might just start with the Range AFM disabler. Shouldn't have to sacrifice good MPG to get a transmission to work right. Sucks that they locked the TCM so it can't be truly tuned by most companies. If I can just get the clunks and delays to go away I'll be a happy man!

[videoarizona]

2015 Sierra 1500 Denali with 6.2/8speed. 70K miles

 

All updates done. All fluid flushes done. Truck shifts almost perfectly all the time. I say "almost"... as every once in a while I get a hard shift, either up or down, to 2nd gear. All other gears are fine. Sometimes the shifts are so smooth, I can't tell what gear I'm in....

 

As far as V4 mode...that is seamless...in or out. At any speed.

 

Crossing fingers my Denali is going to continue this way. She tows my trailer and sailboat flawlessly as well.

 

I am having troubles (still) using cruise control on the hills (was taught to never use CC in hilly country)...but do love the way you set the speed for going downhill as you crest the hill and she will stay darn close to that speed going down...despite the 6K lbs trailer pushing hard!

 

And my TPMS is way off.....to the dealer it will go next chance I get. But that's another story...

 

[Cjc]

On 8/4/2019 at 9:45 AM, YukonXL04 said:

Hmm. Mine had the random cold start shift delay from 1st to 2nd. Might do it 1 time in 2 weeks, might do it 4 times a week. Other than that I love it. Truck runs and drives excellent with that 1 small exception. Taking it to the dealer next week for free oil change, I wonder if I should have them do the Mobil 1 fluid TSB while its there... 

Mine is just like yours.I'm thinking also doing the Mobil 1 change.

[YukonXL04]

On 8/13/2019 at 8:31 AM, Cjc said:

Mine is just like yours.I'm thinking also doing the Mobil 1 change.

Well I went to the dealer and talked with them. They drove the truck, couldn't replicate the problem so no fluid change. Oh well

[Brett carter]

Mass produced trucks with transmission issues, have a 15 high country 1500 6.2, shifts hard, was worse before reprogramed, but is different shifting now, still hits hard, shifting is hard, gm puts updates out for these transmissions because they know there peices of shit!!! They know the issue but it is all about the money. Same thing as everyone has said, it seems like they just want to wait until the warranty is over so your screwed!!!!! Have had it flashed 3 times now and no fix, don’t buy a chevy they are junk, gm won’t stand behind this crap!! Will not buy a Chevy again, I’ll buy a ford before a Chevy and I don’t even like them. 

[STurner15]

On 8/18/2019 at 4:38 PM, YukonXL04 said:

Well I went to the dealer and talked with them. They drove the truck, couldn't replicate the problem so no fluid change. Oh well

TSB doesnt require them to drive the vehicle to complete the latest TSB for hard shift or "rumble strip feeling". Got mine flushed the other day for $300 (barely out of 60k warranty). Long story short, they put in the new blue M1 fluid and it seemed to help a bit.

 

I also have tuned the vehicle to increase the firmness of the shifts, which also helps.  But what I've noticed and maybe worth folks looking into.... the type of gas used, and more importantly where you get the gas from. If I put in Kroger gas, it runs like shit and shifts really hard. Mobile or BP... it shifts very clean. Cheaper than continuously throwing tunes, flushes, etc at the truck... try it out

[MD11G200]

The flush done with the new fluid and it helped tremendously both the shudder my truck eventually developed as well as the horrible clunky downshifting. Hard downshifts not gone but much better.

Through consistently filling out the emails sent to me by GMC to rate the dealer( sent very delineated emails responses to surveys about how pissed off I was after 5 dealership visits and no fix) after work was performed I was contacted by a regional guy from GMC who offered me 3 options to try and help:

1. Have field engineer come out an drive my truck(since flush fixed MOST of the problem elected not to do this)

2. $4500 cash towards the purchase of any new GMC vehicle, I would have to negiote the price with the dealership, then they would apply the $4500 to the deal( don't really trust another new GMC vehicle, so didn't do this)

3. extend my transmission, transfer case and trans axle warranties and all related items another 5 years/75,000 miles from the trucks current mileage. ended up with a warranty on those items good til 01/03/2025 or 118,335. Was best option for me since I drive my truck about 15-18K a year.

 

I would say to anyone having transmission problems be sure and always answer dealership surveys if you receive one. Only time will tell if my transmission starts all the bad clunky cramp and shudder again.

 

Hope this helps someone

[Ford Truck Wanabe]

I have a 2016 GMC 6.2L 8 55k miles 8 speed trany has the shudder problem.

It has always had the clunk but not regularly mostly happened on cold mornings first shift.

Lately the shudder started happening it will happen at highway speeds just cruzin down the road.

So far on the forum I haven't seen any fixes did I miss something?  

[JimCost2014]

On 1/20/2020 at 7:42 AM, MD11G200 said:

The flush done with the new fluid and it helped tremendously both the shudder my truck eventually developed as well as the horrible clunky downshifting. Hard downshifts not gone but much better.

Through consistently filling out the emails sent to me by GMC to rate the dealer( sent very delineated emails responses to surveys about how pissed off I was after 5 dealership visits and no fix) after work was performed I was contacted by a regional guy from GMC who offered me 3 options to try and help:

1. Have field engineer come out an drive my truck(since flush fixed MOST of the problem elected not to do this)

2. $4500 cash towards the purchase of any new GMC vehicle, I would have to negiote the price with the dealership, then they would apply the $4500 to the deal( don't really trust another new GMC vehicle, so didn't do this)

3. extend my transmission, transfer case and trans axle warranties and all related items another 5 years/75,000 miles from the trucks current mileage. ended up with a warranty on those items good til 01/03/2025 or 118,335. Was best option for me since I drive my truck about 15-18K a year.

 

I would say to anyone having transmission problems be sure and always answer dealership surveys if you receive one. Only time will tell if my transmission starts all the bad clunky cramp and shudder again.

 

Hope this helps someone

Your customer service survey goes to GM, then to the owner of the dealerships desk, they do not like seeing them come back when they are bad.

 

If they get too many, they can loose their contract with GM as a dealer.

 

Good job in filling them out truthfully, rather than doing as the dealer requests and answering all questions as completely satisfied.