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Old 09-27-2023, 01:04 PM   #1
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Shimmy in the Chevy!

We are owners of Keystone Montana High Country 2022 295RL. This past weekend we traveled to Maggie Valley, NC. Our first trip going to the mountains of NC. All was well going up the mountain, but coming down the mountain, another story. As we were headed down the mountain near Black Mountain,NC the truck (2020 Chevy Z71 2500HD)began to shimmy just a bit when slowing the truck and camper down. Then it stopped. Then it started up again but this time more violent shimmy as we slowed to the posted 35 mph. It lasted about 4 minutes till we flattened out on the road but it was scary. Hubby said he will take the truck to the Chevy dealership to see about getting the brake rotors checked out and rotated. QUESTION;is this normal? I saw another truck along the road that was pulling a utility trailer with smoke pouring out from under the hood so think his brakes may have overheated. Before we head back on any future mountain trip I want to see how this shimmy can be avoided and settle my nerves?
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Old 09-27-2023, 01:48 PM   #2
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Need a better description of the "shimmy". Was it shaking while applying the brakes? If so not trailer related. Might have a warped rotor. Possibility wheel balance. Neither is a big concern and can be corrected easily.
Tony & Donna
2022 Montana HC, 295RL, Solar Flex 400, Onan 3600 LPG, 2K inverter, 200AH Lithium. 2020 GMC Denali 2500 6.6 Duramax, Demco 21K Auto Slide
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Old 09-27-2023, 07:02 PM   #3
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Sounds like the anti lock feature on the truck brakes was kicking in. Being pushed by the trailer on a down hill slope, the truck doesn't know you are not on ice or slick roads. All it knows is the tires are not gripping the road right, it thinks you are on a slide and the anti-lock brakes start reacting.

That would be my guess.

I've been towing in the Mountains of North Carolina for years now. My first tow was in 1979 with a Chevy Cutless towing a 24 foot long U-haul trailer on a bumper attached hitch on I-40 through Ashville and then on down Black Mountain. That was the first of many, many towing experiences.

The secret to successful and trouble free down-hill towing is drop the transmission into a lower gear and let the engine keep the speed own. That is is the ONLY way to do it. Tap on your brakes only momentarily to hold your speed down. If you have to, slow down even more, and drop into yet a lower gear to keep a safe speed and to not ride the brakes.

Chances are, you've overheated your brakes now. It would be good to have them checked out by a trusted mechanic to make sure they did not warp.

I was a camp host for the Month of July and August at Pilot Mountain State Park near Mount Airy this year. I love those mountains in North Carolina! The Applica and the Blue Ridge mountains make some absolutely magnificent camping!
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Old 09-28-2023, 03:36 AM   #4
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It could also be brand of tires and air pressure in those tires. it takes a lot of time to get brakes that hot unless you have turned the rotors already. Steering dampener could also effect wheel shimmy. tires could be a factor as well Cooper all terrain tire are notorious for shimmy like this especially if slightly under inflated they are many other brands as well that will do this under certain conditions, especially at lower speeds likes you stated. so check tires as well as suspension parts that could be worn. How many mile on the truck?
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Old 09-28-2023, 05:32 AM   #5
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diesel or gas truck? diesel -use the exhaust brake and a lower gear. you got your brakes hot and warped a rotor. you can also use the brake control for the camper brakes to slow down

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Old 09-28-2023, 07:53 AM   #6
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Look on YouTube for
Death wobble.
Happens when you hit a bump running across the road like a bridge seam.
See if you experienced anything like the videos.
I had it twice 2016 F350 dually.
First time they changed the front tires, balanced all of them, changed all the shocks and the steering dampened.
Two years later, same thing.
I changed the shocks and steering dampener (they put put some no name brand on). The front shocks and steering dampener had NO resistance. I changed them all to Bilstein shocks and steering dampener.
Two year later no problem.
Daryl and Marianne,
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Old 09-28-2023, 11:52 AM   #7
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(For us old timers) I have heard of Shimmy shimmy coco bop, but never Shimmy in the Chevy!! LOL

Tom and Gail
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Old 09-29-2023, 07:50 AM   #8
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Chevy and GMC trucks are usually not prone to front end wobble unless a part has worn..

My suggestions :
1. Lift front tires up off ground and check for front wheel bearing failure..
.. grasp tire at 6 and 12 position and try to move tire
.. do same with hands now at 3 and 9 position
.. there should be ZERO motion when trying to wiggle front tires
2. Now with tires still off ground grabneach tore and psi and pull chck9 g the tie rod ends and center link.
.. should be zero free slop movement

I have owned Chevy and gmc trucks for the last 50 years .
They are not prone to “Death Wobble” like some other truck males are

Since you didn’t specify if issue when slowing down was with brakes applied or not you can also check the rotors and pads for evidence of issues

You should also have a steering stabilizer shock absorber but if this was and issue you would feel shimmy at all speeds

My 2007 GMC Duramax Classic is still running original brake pads so I can not believe your brakes would be an issue on a 2020 unless you burn the crap out of them on downhill runs

If you have mechanical skills you should be able to easily find this issue and resolve.. if not any good front end alignment shop will also work..
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Old 10-01-2023, 04:22 PM   #9
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This is a diagnosis that should be left to professionals to resolve not guesses based on inadequate clues/information. Your safety is at stake here. This is something that can elicit panic, and in the right situation, can lead to an improper reaction/s from the driver. I’ve had friends tell of a passenger (usually the ****) react with a blood curdling scream that caused the driver to freeze up, vapor lock, deer in the headlights etc..
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