Lots of chucking and bucking in 2020 HD Diesel High Country.

[Steve Hougham]

On certain roads (mainly some interstates), I get a lot of chucking and bucking pulling a 33 foot 5th wheel.  This one did not come 5th wheel prepped.  I had a Curt under mount hitch installed and use an Anderson Hitch. High Country has the Advanced Trailering package standard I believe but I'm stumped on what to do about this.  I have talked to other owners of 5th wheels and they report not having these issues. I'm considering air bags and I have already installed Timbrens to replace stock bump stops but that really doesn't help. Looking for suggestions.

[unit]

You didn't state the pin weight on your rig or what the door tag shows the max tongue weight to be.  GCWR and total weight of the loaded trailer are also factors.  You may well be overloaded.  Air bags can help control the load but you might really need a 3500 for your load.

[Tomato]

Pin weight is a big factor along with ensuring your rig is level behind the truck. I had the same issue with my 2015 Sierra, and, to a lesser extent, my 2020 DRW - trailer pin weight of 3,200+/-. I went with a FlexAir pin box with the 2015 Sierra, and it eliminated 95% of the chucking. It was too long for my 2020, so I went with the RotaFlex, and it did the trick. I like the RotaFlex much better than the FlexAir, as it is a simpler design, and you don't have to worry about adding air all the time.

[ShotgunZ71]

I pull a Jayco Eagle 355MBQS with my 2500 Denali. The 5er has a Reese GooseBox and pulls great, smooth and very little chucking. Maybe something just needs adjusting to get the balance a little better.

Edited August 9, 2021 by ShotgunZ71

[Njmurvin]

I'm assuming you have the standard bed length? Depending on the nose of your fifth wheel and the position of your kingpin (how forward it is relative to the front of the overhang), you may have some flexibility to try different configurations of your Andersen hitch to move your pin weight more forward in the truck bed.  For example, to bring your pin weight forward, you can either install the hitch in reverse (bringing the ball closer to the cab) or install the kingpin adapter in reverse (moving the red receiver cup back toward the trailer) or both. This all depends on how much clearance you have between the truck cab and the trailer overhang. Obviously, you can't move it too far forward if it causes issues with cab clearance.  I don't know how your Curt receiver was installed. But, the OEM gooseneck package places the gooseneck receiver slightly rear of the axle. The Andersen hitch's offsets add up to 9" to that and may be putting your pin weight too far back in the bed.

 

FWIW, I have a standard bed with the OEM gooseneck/5th wheel pucks and the Andersen Ultimate Hitch installed as far back as possible. I don't experience the chucking you describe. But, my truck is a 3500 and my trailer is only 28'. So, that might explain the difference.

Edited August 8, 2021 by Njmurvin

[KMacinAZ]

I had a 2019 3500 dually with the Andersen pulling a 19k 42’ fifth wheel and had what seemed like a lot of “bucking” (MorRyde pinbox). I switched to a 2020 dually and a Gen-Y hitch and received no improvement and maybe a worse ride.  There are a few variables here so no conclusions drawn yet and is still a work in progress.

[2020-2500]

On 8/6/2021 at 5:50 PM, Steve Hougham said:

I had a Curt under mount hitch installed and use an Anderson Hitch.

 

I've got this same setup on a 2500 custom with no issues with a 37' 12,000lb 5th wheel.  I'd be curious about your pin weight, trailer weight, and what the sticker on the door jamb says for load capacity.  The High Countries typically have a lower capacity than the customs which could play a factor.

 

How many times have you towed with this setup?  It's been a while but our first trip the 5th wheel was empty and I remember it chucking a bunch.  Calmed down once we filled it up.  Does this only happen in construction zones or otherwise poor quality roads?

[trkpro]

I've got a 2020  3500HD with the same problem.  It stumbles when I'm towing.  I took it to a Chevy tech and was told he's seen several of them with this problem.  His best guess was that it involved the 10 speed searching when you first touch the throttle when you coast a little and then start to slowly accelerate.  It does not do this when I'm using cruise control, only when operating throttle manually.  I also have the Anderson hitch, air bags, etc.  This is not chucking from the fifth wheel, as a retired driver, I know the difference.  This is a computer problem in my opinion.  It's similar to the old carbs that used to stumble if the accelerator plunger was worn out.  This should not happen to a vehicle run by computer programing.  I think Chevy needs to step up and correct this issue!

[brockhals]

I'm having this issue (I think) pulling my boat.  New trailer, surge brakes on both axles, likely 7K or so loaded up.  This started a couple trips back and almost feels like the truck is missing or the trans is slipping when maintaining speed, whether on cruise or not.  When accelerating or decelerating, it's nice and smooth, otherwise kind of jumping all over the place.  of course, no issues with no load so it's hard to duplicate without taking my boat to the dealer.

[GMC4Zee]

On 9/21/2021 at 11:23 PM, trkpro said:

I've got a 2020  3500HD with the same problem.  It stumbles when I'm towing.  I took it to a Chevy tech and was told he's seen several of them with this problem.  His best guess was that it involved the 10 speed searching when you first touch the throttle when you coast a little and then start to slowly accelerate.  It does not do this when I'm using cruise control, only when operating throttle manually.  I also have the Anderson hitch, air bags, etc.  This is not chucking from the fifth wheel, as a retired driver, I know the difference.  This is a computer problem in my opinion.  It's similar to the old carbs that used to stumble if the accelerator plunger was worn out.  This should not happen to a vehicle run by computer programing.  I think Chevy needs to step up and correct this issue!

The 2020 3500 gasser does not have a 10 speed. It only came with a 6 speed. 

I get some chunking with my '21 3500 AT4. I dont believe its the truck as it still happens when I let off the gas. I have the Andersen hitch and MorRyde pinbox. It seems to happen when the trailer (32' 12K ) is bouncing. So I have heavier leaf springs and shocks to install on it for next season. No trailer bounce should equal no chunking I hope. Andersen is installed normally with the cup toward the trailer and plenty of clearance to do up to 90 degree turns as the new HD's have 6'10" boxes.

 

Edited October 13, 2021 by GMC4Zee

[sheath]

I've had real good luck with the Roto-flex pin box on a 37' 5th wheel (14,580lbs loaded with a 3,480lbs pin weight).  It came stock, and when I saw it my first thought was "another gimmick". I actually rolled my eyes when the sales guy started talking about it... lol 

If the undulations in the road surface are just right I can just barely feel a bit of chuck, but nothing that would even slow down drinking a cup of coffee in my favorite mug.

I watch the hitch in the bed, and it's working pretty hard both lateral, and in rotational flex, so it is definitely making a difference.  Might be worth asking about.  But it doesn't work well with the Anderson hitch setup, because the Anderson Hitch requires locking out the rotator.  In my case that rotator is working in conjunction with the urethane pad to limit the chucking. So you would probably want to borrow a standard 5th wheel hitch to try it with.