New AT4X HD owner here.

[pinebaron]

I have the HD AT4X gasser. Had it for almost 2 months now, about 6k miles, mostly highway with a few trips on some northern Michigan trails. Absolutely no vibrations on the highway at any speeds. I do sometimes get a little whine noise that I haven’t figured out yet, but the ride itself is smooth.

Do you have the AEV edition? I think I just got unlucky; apart from the impending wheel alignment scheduled on the 10th, I'm left pretty high and dry to figure this out myself. What is good to know, following new owners reviews like yours, is that it is not an inherent issue with the design, just my truck only, just need to figure out exactly what. Following wheel alignment, the only thing left would be defective shocks and that is going to be hard to prove to GMC. Following wheel alignment, I may take this vehicle across the border to Canada where I may have a sympathetic GMC dealer/mechanic.

 

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[Bregea1]

Do you have the AEV edition? I think I just got unlucky; apart from the impending wheel alignment scheduled on the 10th, I'm left pretty high and dry to figure this out myself. What is good to know, following new owners reviews like yours, is that it is not an inherent issue with the design, just my truck only, just need to figure out exactly what. Following wheel alignment, the only thing left would be defective shocks and that is going to be hard to prove to GMC. Following wheel alignment, I may take this vehicle across the border to Canada where I may have a sympathetic GMC dealer/mechanic.

Mine is not the AEV, so I have different wheels, but the suspension / shocks are the same. It would be if it’s alignment straight from the factory, but fingers crossed for you that it could be that simple.

 

[pinebaron]

Mine is not the AEV, so I have different wheels, but the suspension / shocks are the same. It would be if it’s alignment straight from the factory, but fingers crossed for you that it could be that simple.

I am hoping for a miracle.

 

[WyomingAT4XAEV]

Do you have the AEV edition? I think I just got unlucky; apart from the impending wheel alignment scheduled on the 10th, I'm left pretty high and dry to figure this out myself. What is good to know, following new owners reviews like yours, is that it is not an inherent issue with the design, just my truck only, just need to figure out exactly what. Following wheel alignment, the only thing left would be defective shocks and that is going to be hard to prove to GMC. Following wheel alignment, I may take this vehicle across the border to Canada where I may have a sympathetic GMC dealer/mechanic.

I suspect that the shocks are probably ok based on the fact that the first 100 miles of driving were fine then the vibration started after a hard acceleration. That would not affect the shocks. I think that your issue may be drivetrain related with something out of balance on either the driveshaft, bushing etc. You can see most of the driveshaft behind the skid plates all the way to the rear differential just by bending down. May be worth mounting a gopro or other camera underneath (or crouching next to the truck as it drives slowly by) to see if the driveshaft looks like it is turning true and not tweaked. Or you can put it on a lift and put it in drive and without giving it any gas you can see if the driveshaft is out of whack. Even a little bit will cause a big vibration at highway speeds.

 

[pinebaron]

I suspect that the shocks are probably ok based on the fact that the first 100 miles of driving were fine then the vibration started after a hard acceleration. That would not affect the shocks. I think that your issue may be drivetrain related with something out of balance on either the driveshaft, bushing etc. You can see most of the driveshaft behind the skid plates all the way to the rear differential just by bending down. May be worth mounting a gopro or other camera underneath (or crouching next to the truck as it drives slowly by) to see if the driveshaft looks like it is turning true and not tweaked. Or you can put it on a lift and put it in drive and without giving it any gas you can see if the driveshaft is out of whack. Even a little bit will cause a big vibration at highway speeds.

Any possibilities exist. My gopro is so old it won't do the job but I will try to get one. I don't yet have access to a lift, have often thought of installing one; my local mechanic with his 10,000lb two post lift was hesitant to raise it up; he just worked with it on the floor. I'll request the local GMC dealer to examine it during the alignment appointment.
I may have mentioned it somewhere but once it starts oscillating, it keeps doing that all the way to stop, it sort of gets into a perpetual motion. The hard acceleration may have lossened or freed up some component and the drive shaft is definitely one to look into. Its easy to get under this beast, the rear drive shaft, enough to drive a tank, shows no sign of play, not sure if we checked the front while the skid plate was off. Its all a darn mystery.

 

[BuckWallace]

Those AEV wheels look amazing. If any of you guys with an AEV get sick of the wheels and want to sell, let me know .

 

[pinebaron]

Those AEV wheels look amazing. If any of you guys with an AEV get sick of the wheels and want to sell, let me know

Yes they do. Now if I could only get this beautiful truck to stop behaving like a bucking horse on some roads, life would be bliss.

 

[pinebaron]

Good new in that I'm going to test drive a new AT4X (non AEV) this evening at my local dealer, he just got it in today. For the first time I'll be able to compare the two knowing my AEV has steel bumpers and skid plates else its pretty close.

Got there and the vehicle wasn't ready, it was still waiting for PDI.

 

[DRN]

Have you had a road force balance done or was it already mentioned? I chased an issue like this before on a truck and it was the tires. It was 90% better after new tires and when they were road force balanced, one of the new ones was bad. After it was replaced it was the best the truck ever rode.

AND… congrats to the OP on his truck, nice!

 

[pinebaron]

Yes I had road force balance done with OEM tires, the tests failed and that did not change anything. I replaced all five tires and that did not change anything. I have scheduled 4 wheel alignment on Monday and will ask them to road force balance my wheels (now with new tires), may have to pay but its ok.

This morning I had an opportunity to try out a brand new identical truck which the dealer got yesterday (all same specs except AEV edition) and it has exactly the same bouncing issues, zero difference, mine is marginally better due to even better tires. That goes to prove that other new owners here are either driving on perfect roads, hauling loads and have not noticed or objected to rear bounce (which I have now narrowed it down to) and consider it a feature of these new pickup trucks. Others have said time and time again, if ones looking for a softer ride, get a 1/2 ton; 3/4 or 1 tons are designed to haul and are not cadillacs out of the factory. Where does that leave me. Now that I know this issue or feature is inherent in these trucks, I can look for mods/solutions to improve the ride.

I'll report back with an update on Monday.

 

[pinebaron]

On the way back from Whistler, emissions light came on; it did not impact driving or anything. During the appt. back at the dealer this morning, they performed an ECU/TCM update and now its fine. For wheel alignment, it needed a 0.1 degree toe in adjustment on the front right wheel. They did not perform a road force test due to aggressive after market tires; I think I have to live with that.
Finally, the 285 mile drive to Whistler BC and back was uneventful, the roads are pretty good, with lower tire pressures, it ran fine. As stated in my earlier post, the bounce on undulating roads, driving an empty truck, is not going to go away without rear suspension mods. Options are removing a leaf from rear leaf springs, replacing the rear fancy shocks with aftermarket ones or playing around with torsion bar bolts. Since wife did not complain about the long drive, I may leave things alone until I hear about mods by other AEV owners and learn to accept it as is.

 

[JDAT4X]

Potential for engine mount failure (when accelerating to pass on the first drive home from dealer)….torque causing vibration as only one mount in place. May not be able to see when engine off as it sits back in place…..why not take back to dealer even with the distance….? If warranty issue must be logged at lower miles for your best benefit long term…

 

[pinebaron]

Potential for engine mount failure (when accelerating to pass on the first drive home from dealer)….torque causing vibration as only one mount in place. May not be able to see when engine off as it sits back in place…..why not take back to dealer even with the distance….? If warranty issue must be logged at lower miles for your best benefit long term…

I will schedule an appt with a dealer across the border in Canada, the mechanic there is extremely knowlegeable and the service manager is very cooperative.

 

[Lawdog800]

I have the HD AT4X gasser. Had it for almost 2 months now, about 6k miles, mostly highway with a few trips on some northern Michigan trails. Absolutely no vibrations on the highway at any speeds. I do sometimes get a little whine noise that I haven’t figured out yet, but the ride itself is smooth.

What kind of Mileage on the Gasser? I'm near Pontiac

 

[gemarsh]

Its good to hear your ride quality is so good which means theres hope for me. I'll see if I can fire up my old go pro 4 which I have not used in almost nine years.

What's up with the painters tape all over the concrete floor? Are you using your side view cameras to pull in straight?