HARD SHIFTING in a 2016 Yukon Denali 6.2 with 8 speed

[donniegilbert]

I recently purchased a 2016 Yukon XL Denali with 90K miles. Even on the test drive, I thought that the 1-2 shift was a bit harsh. Well, even after being at the GMC dealer several times it STILL shifts harsh... or sometimes it decides it doesn't like second gear at all and skips that gear, basically going from 1st to neutral to 3rd... with a large spike in RPM's sometimes bumping off of the Rev limiter dependsing on where my foot is on the pedal.

 

Here's what has been done.

 

P0711 code was found. A new Trans Temp sensor was installed. Fluid Flushed with the newer Mobil 1 fluid as per a TSB for Shutter condition.

A QUICK LEARN was done for the TCM.
Result - No difference in shifting. 1-2 bangs in (especially on cold start up). At WIDE OPEN THROTTLE, 1st is good, then when shifting out of 1st, it goes into neutral, engines hits the REV limiter, 2nd SLAMS into gear, rear wheels chirp, then shifts into 3rd. The rest of the gears are fine.

 

Second trip to the dealer. An EXTENDED LEARN with Individual Clutch Pack reprogramming was done on the TCM. Basically the same result as above.

  

BUT........... Sometimes the dumb thing shifts like it is supposed to, so to me, that indicates that the internals of the transmission as working, but only WHEN THE COMPUTER DOES IT'S JOB RIGHT !!!!

 

I have looked through previous posts, printed them for the tech at the dealer, he read them, and basically he said that there is nothing he is capable of doing.

 

On a different note, I spoke to a 2016 Yukon owner last night, and he said that he got a Transmission Recall notice in the mail a few days ago, but he didn't read all the details, but he experienced the same issues as me. So I looked up recalls on the GM web site, and my VIN says that there are none.

 

What is going on everyone and what can I do to fix this thing? I bought it to tow a trailer. I can't have it missing shifts.

 

Thanks

  

Donnie 
 

Sorry... I saw that I posted this in the Silverado Group by accident.

[GMC8810]

Any luck? I am having the exact same issues.

 

I mean exact same:

 

2016 Denali 78k miles.

Code thrown. Replaced  transmission temperature sensor, new fluid, quick learn, etc..

 

Same exact symptoms.

 

Extremely frustrating as I never expected this type of crap from what's basically a GM truck drive train.

 

 

[flyingfool]

yeah you guys with higher miles that havent removed the Thermostat in the trans might be having issues do to the high temps from the stock configuration 200+degrees. heat kills the sensitive plactics, clutches and electronics like Tecum next to the valve body in the 6l80e models, some of the valvebody check balls are also plastic and tend to shrink from the heat and dont do thier job checking flow in the valvebody resulting in a neutral condition when you should be in 2nd ..

 

you can do the trans relearn by purchasing the vcm nano tech 2 clone on amazon, this will reset the trans learn function. watch a couple tech vids on YT

call the techs at Circle D transmission, they know more than the GM mechanics. sounds like its rebuild time with upgraded parts

Edited March 4, 2020 by flyingfool

[homer12]

Is the 8-speed tranny in the 6.2’s almost guaranteed to have these kinds of issues? Sorry, not looking to threadjack but very interested I a used one myself

[mjm-1957]

Stay away from the 8 speed at all costs. Absolutely  horrible.

[flyingfool]

i believe the Tecm is on its way out , one of the solenoids might be bad, these newer trans are very simple mechanically compared to the older 4l60's, they're nothing but a bunch of clutch baskets lined up in a row, and a couple sungears , there aren't any bands or band pistons anymore. 

 

trans shop should have the pressure tester to mount on to the Tecm unit to test it out. 

[flyingfool]

On 3/6/2020 at 9:16 AM, mjm-1957 said:

Stay away from the 8 speed at all costs. Absolutely  horrible.

8 speed has been De-tuned, the Camaro guys love em. 

they need the Camaro Upgrade parts and software flash to work right , I'm willing to bet the trans pump Boost valve is larger on the Camaros SS too , better line pressure firmer shifts...

Edited March 9, 2020 by flyingfool

[Mandalorian]

On 3/6/2020 at 11:47 AM, homer12 said:

Is the 8-speed tranny in the 6.2’s almost guaranteed to have these kinds of issues? Sorry, not looking to threadjack but very interested I a used one myself

Not 100%, but more than a reasonable doubt. The 8-speed was flawed from the beginning as it was sort of thrown together as a stop-gap until the 10-speed co-developed with Ford was ready. 

[IndyRob K.]

I have the dreaded 8 speed, it does jerk from first into second but after that its good. I am currently reading up a getting a trans tune to lower temps.

[Tahoe02]

Have you done the fluid change to the fluid recommended in the TSB.

[RussellF]

I have a 2016 Yukon Denali with 50,000 miles,  I have an extended warranty and the drive train is still under manufactures warranty.  The truck went into the dealer for hard shifting from start.  The dealer ship had the vehicle for 2 weeks.  Now I have smooth shifting from start, but downshifting between 5mph and 3mph coming to a stop there is a hard shift.  The dealer is telling me because it is a learning transmission I need to wait 400-500 miles.  Is this true?

[Joseph Randazzo]

There is some truth to that but mine has 28000 and still does it under certain conditions but not on every stop.Dealer says its normal.. Something is amiss in the programming between the V4 /V8 mode and downshifting. Apparently no fix for this.