2020 GMC 2500 HD DENALI TRANSMISSION PROBLEMS

[tkcrane89]

We bought our 2020 HD less than 4 months ago & its been in the shop 2 different times with transmission problems.  Its been in the shop a total of 6 weeks.  The first time we were told after 3 weeks it was fixed.  Now 3 weeks later it won't move forward but you move in reverse as far as you want.  When I put it in drive it shifts so hard it will throw you forward in the seat.  It first started when we had it 2 weeks.  Talk about being disappointed. We are making payments on a near $80,000 vehicle that we are not even able to use.  I was just wondering if anyone else has had any problems with the transmission. 

[Cool J]

Is this a Duramax?

[cNate]

Research the lemon law in your area and force them to buy the truck back.

I have a 2020 2500 AT4 HD 6.6L Duramax. I’ve had it 7 weeks and 2k miles (about 800 of them towing from sea level to 8k ft elevation and back). No transmission issues. Transmission is the smoothest I’ve had out of the 7 GM vehicles I’ve owned over the years.


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[Kmac 2020]

My 2020 was in the shop last week and they told me I needed a new transmission shift module 

 

[Sonny James]

I have a 2020 3500HD Duramax Diesel Denali and think I have a transmission issue at just over 500 miles.  The first time I went up to 74MPH I heard a hollow howling type noise that seemed to come from the front right of the truck. My passenger stated he thought he felt the floor vibrating and it sounded like it was coming from the rear.  

 

What I have learned is if I put the transmission in manual shift, then do 74, I hear the noise in 10th gear.  If I downshift from 10th to 9th the noise goes away.  If while in 9th gear I slow down to 68, the noise comes back until I downshift into 8th.  When hearing this noise, both times the tach was exactly at 1500RPM.  

 

Also, when accelerating if I hear the noise at lower speeds and look at the tach, it is at 1500RPM.  Anyone else having this issue?

Edited January 18, 2020 by Sonny James
Added Diesel

[JBRLLC]

I've got a 2020 3500 GMC Denali with 27k mileage on it. This same problem just sent this one to the shop. Hard shift if it would engage at all. High rpms that would barley move the truck. Also this started when in 4 wheel drive and the throttle was surging if the truck slipped in the snow. Strange to say the least but it the first issue I've experienced. Been a good truck otherwise. Did they every figure yours out?