2021 GMC SIERRA 1500 AT4, 3.0 L TURBO DURMAX

Vkk · February 28, 2025

I got 2021 GMC Sierra 1500 AT4 3L turbo diesel,It is still under Warranty , truck is having abnormal noise and vibration while accelerating, only felt noise and vibration at high speed on high way, truck got 60000 kms,( Noise is like humming but rhythmic not constant like bearing, and only if you accelerate if you let go the accelerate, noise goes away even on high speed). I went to see dealer to address the issue, first they took the test drive and told me that they could not see or hear any noise on high way speed. so I asked the manager to get test drive with me So he sent his shop foreman with me on test drive, he felt the noise and vibration so I dropped my truck for troubleshooting.

few days later I got response from them that they collected some vibration data and they have abnormal vibration coming from rear end, so they were waiting for an approval to open rear differential for inspection, one they received an approval from their engineering team, they opened and they looked at the oil and they saw some scoring on main gear, they measured the backlash and they found 0.010", they said according to GM standard backlash has to be 4-6 thou and allowable upto 10 thou, which is I have right now so I was asked to drive the truck for some kms and come back and they will look at it again and see that is issue or NO.

After driving another 1300 kms I went back and I dropped my truck for 2 days, only they did is took the test drive and told me they haven't felt any vibration or noise on highway speed 110km/h. So I said you can feel it if you go on speed above 115km/h and advisor told me No. truck is made for 110km/h according to the ministry of transportation high way speed limit, I said there is a vibration and noise coming for sure but for human being to feel that noise/vibration you have to go on that speed, SO now they are changing their statement that they collected torque converter data and sent it to their engineers to investigate further. And, they found nothing than normal from torque convertor so now what ?

this point I involved GM Canada, submitted a case and it has been a week but still no response at all from them as well, I tried to get an updates from both side GM canada and dealership, GM canada told me they are still waiting some information from dealer, I thought GMC has good reputation for their service and warranty standard but I would give zero to them. I am still waiting for some response and solution from them. I have been working on this since January 17, 2025. filed a case to GM Canada on February 21, 2025. still nothing..

I am looking for some suggestion if anybody facing some issues....

redwngr · February 28, 2025

Service advisers 110 kph argument is bullcrap and they (should) know it.

The dealers management and GM proper should be embarrassed that any service adviser said that.

If you end up talking with GM Canada's Oshawa office, ask how fast they need to run on 401 from Oshawa to Pearson airport....

Or when running north to Barrie and on to cottage country...

If 100 kph was real, why is the trucks speed limiter 160ish?

What happens if the truck is taken to US and run on one of the 80 mph (128kph) speed limit interstates or the 85mph (137 kph) locations?

Fwiw ran mine for many miles at 80 mph or above while on tour last summer.

Silky smooth at all time.

They also know that there is not a different version of the differential for US vs Can.

Edited February 28, 2025 by redwngr

newdude · February 28, 2025

2 hours ago, Vkk said:

After driving another 1300 kms I went back and I dropped my truck for 2 days, only they did is took the test drive and told me they haven't felt any vibration or noise on highway speed 110km/h. So I said you can feel it if you go on speed above 115km/h and advisor told me No. truck is made for 110km/h according to the ministry of transportation high way speed limit, I said there is a vibration and noise coming for sure but for human being to feel that noise/vibration you have to go on that speed, SO now they are changing their statement that they collected torque converter data and sent it to their engineers to investigate further. And, they found nothing than normal from torque convertor so now what ?

If they won't drive it pas 110kmh (68mph), you drive it and tell them to ride shotgun with the test equipment to duplicate it. They are giving you a liability for going over the speed limit excuse is all they are doing, not anything to do with how the truck is made.

The speed governors on these trucks are anywhere from 98mph (157kmh) to 112mph (180kmh) depending on the build of the truck.

Z45 · March 1, 2025

I had a similar situation involving speed limits with a dealer once. Speed limit here was 55 and my tires would shake over 60 mph. Service manager would not permit his techs break the speed limit to road test nor could they ride with me if I drove over the speed limit (endanger their lives, his words). No amount of conversation would change his mind so I had to seek a tire shop to balance the tires and eat the cost. Even thought I bought new there, never been back since.

Edited March 1, 2025 by Z45

Transient · March 2, 2025

And people wonder why I bother learning how to fix my truck myself. The hundreds of dollars I spend on service manuals is so worth it.

Vkk · March 17, 2025

Finally I made big thing against dealership, case is gone higher to executive review team, Now dealership is saying nothing wrong with powertrain, they’re thinking rear tires need balancing, due to off balancing it causing having noise on speed at 120km/h. I asked them to do balancing and prove me, they refused and said I will not get any services at this dealer as I posted bad reviews and complaint to GM higher case Center. But, I told GM executive review team that at my expense they have to prove me that noise is coming due to off balancing, but according to my knowledge if it’s related to tires then noise has to keep coming at any certain speed with continuous but my case it is coming only if you accelerate, if you let go the pedal noise goes away even at 140km/h. That’s my argument. They’re still figuring out.

silveradosid · March 18, 2025

i had this problem with my 2014, 4 times to the dealership and a different answer each time i left. my problem was at 90 and 120 klm's, the 3rd time i went back they took the wheels off a brand new truck and put them on mine, even though they said there was no problem. i asked if they were driving it at 90k and that's when i found out about the speed thing, all the roads were only 60. so i told them i will drive with the tech. then the svc manger says this is the 4th time that no problem has been found and we are not doing anymore. when i was leaving po'ed the tech handed me some papers and said have this test done. i am a mechanic with a big shop so i did the test to GM specs and videoed it. the test was for the driveshaft and it was way out of spec. i took the video to the svc manager and showed him and asked why this wasn't done. no answer but to say my truck has been tested with no problems found end of case. i went to the parts counter and ordered the shaft, 900 bucks and then the svc manager comes over and says something to the parts guy and now the shaft is only 350. that svc manager was fired a week later due to all the complaints

Vkk · March 18, 2025

1 hour ago, silveradosid said:

i had this problem with my 2014, 4 times to the dealership and a different answer each time i left. my problem was at 90 and 120 klm's, the 3rd time i went back they took the wheels off a brand new truck and put them on mine, even though they said there was no problem. i asked if they were driving it at 90k and that's when i found out about the speed thing, all the roads were only 60. so i told them i will drive with the tech. then the svc manger says this is the 4th time that no problem has been found and we are not doing anymore. when i was leaving po'ed the tech handed me some papers and said have this test done. i am a mechanic with a big shop so i did the test to GM specs and videoed it. the test was for the driveshaft and it was way out of spec. i took the video to the svc manager and showed him and asked why this wasn't done. no answer but to say my truck has been tested with no problems found end of case. i went to the parts counter and ordered the shaft, 900 bucks and then the svc manager comes over and says something to the parts guy and now the shaft is only 350. that svc manager was fired a week later due to all the complaints

For me they inspected U-joints, opened rear diff, measured backlash and checked torque converter, trier torque converter ON/OFF manually if any changes happened but so far nothing, So May be i have the same issue that you had related to drive shaft.

are you having Humming noise with bit vibration but only while accelerating ? It’s not constantly though?

silveradosid · March 20, 2025

it was only when i was on the throttle at 90 and 120, it was a pulsating hum and vibration

Vkk · March 20, 2025

3 hours ago, silveradosid said:

it was only when i was on the throttle at 90 and 120, it was a pulsating hum and vibration

Same thing for me, but still dealing with them, Apparently they said No further repairs required as everything under acceptable conditions. So Now I filed dispute to CAMVAP to get decision. There we’re offering me $250 gift card with 2 complimentary oil change.

Edited March 20, 2025 by Vkk