Fifth wheel Jerking with gas truck... not as noticeable

[Part-Timer]

Hello all. First time poster long time lurker. I have been visiting this forum for years. You all are a wealth of information and knowledge. I appreciate all of the expertise on here and you have helped me tremendously over the last decade or so of RVing.I felt the need to create an account and post since I tried searching this forum and many others for an answer but have yet to be able to find one.

Long story short. I have a 2021 chaparral 298rls 5th wheel and a 2024 silverado 3500 gas with 10-speed allison. I have the factory gm puck system and factory curt hitch mounted in the bed holes. My rv tends to "jerk" almost like a fish biting on a line feeling but only when accelerating. Sometimes it is much more noticeable than others... it's hard to describe the feeling, it is NOT chucking like you feel when hitting expansion joints or bumps. It is almost as if the brakes are pulsing 5-6 times a second like a quick "tug - tug - tug - tug -tug" feeling. Sometimes enough to jerk the truck and occupants, sometimes more of just a feeling in the wheel, seat, and gas pedal.

This happened on my old 2022 gas 2500 truck with the same trailer and hitch. Mainly under harder acceleration between 2800-3700 rpms then goes went away after 3700 rpm or so...

I took it to the dealership and they replaced the torque converter and when that didn't fix it, they replaced the transmission pump as one of the fins on the pump had a crack after inspection. That didn't fix it either. A new transmission was on backorder at the time so I decided to trade the truck for a diesel as it was all that they had at the moment. New truck was a duramax and 10-speed allison.

The diesel occaisionally did the same thing but not nearly as noticeable... mainly just slow accelleration in stop and go traffic. But this at least let me know that it was the trailer in some way doing it and not the truck. I learned to live with it and pulled for another 5000 miles or so with 3 different diesel HD silverados all 10-speed allisons.

Fast forward to today. I traded my last diesel for a new 2024 gas 6.6 with the 10-speed allison as I really don't need a diesel for my uses. (Trailer is roughly 12,000 lbs loaded)

Figured the new allison like the diesels would feel the same, but almost immediately I noticed the jerking again under acceleration. Much more prominent with the gas trucks than with the diesel trucks.

Starting with the original gas truck I tried all kinds of trouble shooting from hitch adjustment, pin box adjustments, adding timbren ses to lessen rear sag, different tire pressures in the rear tires, filling my truck bed with hundreds of pounds of tools, filling the water tanks, emptying the water tanks etc..


Now that I'm back in gas truck I am noticing it again and it's much more prominent than in the diesel trucks. IDK if that's due to the additional weight of the diesel engine over the front axle or possibly just the additional mass lessening the "felt" tugging.

We also just replaced all the factory china bomb tires with Goodyear endurance tires after another costly blowout and still feels the same. So that rules out the trailer tires which was my last guess.

Has anyone experienced this before or have any insight? Again, it is not chucking like when you hit an expansion joint. The road can be perfectly smooth and as you start to accelerate or "pull" the trailer at more than just a leisurely pace, it'll start "tugging" 5-6 times a second. This goes away after 3800 rpm or so all the way to 5000 rpm.

With the timbren SES the trucks sits almost level, the rear is still about an inch higher than the front. My old truck had this issue both before and after the timbrens so I know it's not the angle or rake of the truck.

Any insight would be greatly appreaciated.

[Part-Timer]

I have entertained the idea of the Andersen goosneck adapter. Hard to convince the wife of the cost when I have a "perfectly-good" hitch now. I like the convenience idea of the Andersen and the light weight in/out removal concept especially compared to the 200lbs of cast iron that I have to deal with now. But I'd hate to spend the money just to have the same jerking that I'm feeling now. As for normal "chucking" common to fifth wheels... I really don't have any to speak of. It really does pull and track well and the handling is great. Just this tugging sensation when accelerating at certain rpms is mind boggling.

[cummins2014]

Cummins12V98 wrote:
EASY!!!

It's your CURT hitch. Look at how low the pivot point is on the CURT. FACT it can cause a chucking feeling.

Compare to the B&W that has it's pivot point at the height of the kingpin.

What took you so long . It's sure possible it's the hitch . He is a great candidate for the Andersen , and IMO would solve his problem . I am sure you will agree on the Andersen with the weight he has , no need for some expensive hitch .

[Cummins12V98]

EASY!!!

It's your CURT hitch. Look at how low the pivot point is on the CURT. FACT it can cause a chucking feeling.

Compare to the B&W that has it's pivot point at the height of the kingpin.

[Part-Timer]

Durb wrote:
Unplug your trailer cord from the truck (no brakes) and see if it persists. If yes, then disconnect your battery which will disarm your breakaway switch which I suspect is your culprit. Test your rig in a safe zone.

It sounds like there is an electrical malfunction that is applying your brakes during acceleration; a tough problem to locate. As you accelerate, a circuit closes and the brakes are applied which causes deceleration which causes the circuit to open and allows you to accelerate again repeating the process, thus the jerking.

I had a motorcycle once (BSA Victor) that would die under acceleration, then start up again under deceleration. Quite humorous actually, jerking and wheelies. Turned out the battery was sliding back and forth in the battery box and was shorting against the frame.

One other question or thought on this. When I am accelerating and the jerking/tugging starts, if I squeeze the manual over-ride on the brake controller, the tugging sensation does not stop... the amount felt within the vehicle is dampened due to the brakes dragging on the entire truck/trailer rig but you can still feel the quick "tug- tug-tug-tug-tug" feeling. It's almost like if I had a misfire in the engine. That's the closest I can describe the feeling. I would assume that when I manually apply the brakes from the brake controller that it would override a fluctuating signal from a faulty breakaway switch?

[Part-Timer]

Durb wrote:
Unplug your trailer cord from the truck (no brakes) and see if it persists. If yes, then disconnect your battery which will disarm your breakaway switch which I suspect is your culprit. Test your rig in a safe zone.

It sounds like there is an electrical malfunction that is applying your brakes during acceleration; a tough problem to locate. As you accelerate, a circuit closes and the brakes are applied which causes deceleration which causes the circuit to open and allows you to accelerate again repeating the process, thus the jerking.

I had a motorcycle once (BSA Victor) that would die under acceleration, then start up again under deceleration. Quite humorous actually, jerking and wheelies. Turned out the battery was sliding back and forth in the battery box and was shorting against the frame.

As stated in a previous post I have tested towing with and without the trailer wiring connected. It does the tugging even without the 7 pin connected. This was done on a low traffic side street and safe.

I have not tried disconnecting the trailer battery to reset anything, however the battery did die last month since my wife left some lights on and I didn't have it plugged up to shore power. It was dead without power for about two weeks before I towed it on our most recent trip. The battery was good and charged by the time we got to disney from Savannah, Ga. Not sure if a dead battery for two weeks would reset anything any different that simply disconnecting the battery does. I would assume it would have the same effect

Edited to add*** Sorry, I read that wrong... I understand what you're saying now and that makes sense. I will try that the next time I tow it. thanks

[Durb]

Unplug your trailer cord from the truck (no brakes) and see if it persists. If yes, then disconnect your battery which will disarm your breakaway switch which I suspect is your culprit. Test your rig in a safe zone.

It sounds like there is an electrical malfunction that is applying your brakes during acceleration; a tough problem to locate. As you accelerate, a circuit closes and the brakes are applied which causes deceleration which causes the circuit to open and allows you to accelerate again repeating the process, thus the jerking.

I had a motorcycle once (BSA Victor) that would die under acceleration, then start up again under deceleration. Quite humorous actually, jerking and wheelies. Turned out the battery was sliding back and forth in the battery box and was shorting against the frame.

[Part-Timer]

Hopefully this image upload works

[Part-Timer]

I haven't checked the suspension, I'll have to crawl under it when I get a chance. I will say that Tuesday morning I had 5 new tires installed and had to jack it up myself since the shop didn't have a large enough jack or stands. I didn't notice anything weird with the suspension when I had the wheels off but I did trace the wires going to and from the brakes into the axle and didn't see any cracks or chafing any where on the wires, at least the visible portions.

The pinbox is the factory pinbox that came with the trailer, its a lippert frame so I assume a lippert pinbox but I honestly do not know for sure. I can check when I get home.

Current truck is a short bed with the factory puck system, hitch is about 3 inches behind the centerline of the rear axle. However my last truck was a 3500 duramax single rear wheel with the 8ft box. Same factory puck systema and hitch but the hitch was square with the rear axle. This truck also had the occaisional tugging at low speed acceleration but less noticeable... my theory is due to the additional mass of the diesel engine. But my point is the tugging was still there with the diesel and the long bed truck.

Would a possible brake malfunction in the trailer brakes cause this issue? As-in a defect in the shoes or drums or physical hardware?

On my first truck that had the torque converter replaced, the dealer tech rode with me to feel the tugging and we pulled the trailer with and without the connector plugged in to elliminate the brake controller. The tugging was there even without power to the trailer or braking system.

Honestly at a dead end with my trouble shooting ideas which is why I made the post.

The trailer has 8600 miles on it currently but has done this since new. Always assumed it was the truck or hitch. I have blown two factory chinese trail ride tires. Again, assuming that the tires were just cheap and unrealted to the tugging. Could sticky/malfunctioning brakes cause tugging only during acceleration and only at certain rpms/linear pull loads? and what I mean by linear pull loads, it's like at certain amounts physical pulling from the truck is when this happens. It does NOT happen cruising down the road, slowing down or when applying the truck or trailer brakes to stop. Only under acceleration at just the right amount of "pulling force"

I will note that the old tires when filled to 80psi cold, would climb into the mid to high 80's after towing. Even at night with a 70-75 degree ambient temp. And the rubber compound was extremely soft and tread seemed to be melting. Like if you did a sweet burn out in a hot rod and had rubbery residue and string like particles all over your tires. That's how some of the old tires were looking while towing on our last trip and what caused me to buy new tires. I'll try to upload a picture if I can figure it out.

The new tires seemed to only go up to 83psi pulling in the florida heat on our way home during peak sun and 90 degree temps. Also no visible wear after 300 miles.

I was thinking maybe sticking brakes could cause extra friction on the tires causing them to "melt" and blow out. But it could also just be cheap/dangerous tires. Especially since the goodyears appear to not be affected the same way.

[eHoefler]

Short bed truck? Check location of center of hitch to center of axle

[Tvov]

Did you check all the wiring in the 5th wheel? Especially the brake wiring? Maybe there is some sort of odd cross connection or something going on. Kinda sounds like the brakes are pulsing?

[bucky]

What pin box are you running?

[ssthrd]

The trailer seems to be the common denominator. Wondering if the trailer suspension might have a loose bolt or two. Might be worth a look.

[fj12ryder]

That's a new one on me. I don't have a clue, since it has happened with all the trucks.

[Part-Timer]

Also just wanted to add that the hitch and mounting points are solid. When coming to a stop or leaving from a stop there is no "slack" or "clunk" felt in the hitch or pin as I have felt with other hitches over the years.

Another note, when I am accelerating and the tugging begins to happen if I squeeze the brake controller the tugging does not stop. So if I am accelerating and say between 2800-3800 rpms I will feel the quick "tug" "tug" "tug" "tug" feeling and it will continue even if I apply the trailer brakes and continue to accelerate.

I hope that makes sense

[Part-Timer]

Hey, thanks for the response.

This motion happens on all surfaces, smooth or rough doesn't make a difference. It is not the same chucking feeling as when hitting a bump or expansion joint on a bridge or overpass.

** edited to add that I have tried pulling it with the freshwater tank both full and empty which is infront of the axle and would increase the pin weight. The full tank did not make a difference.

No I have never been to a scale to weigh it all. Per the manufacturer website the estimated pin weight is 1,935 lbs, based on an estimated dry weight of 9,574 lbs. Those two weights come from their website and the pin weight is 20.2% based on their weight measurements. The dry weight as shipped from the manufacturer per the sticker on the pinbox is 10,870 lbs.

We also added a washer and dryer to the front of the coach driectly above the pin box in the nose/closet and the propane tanks as well as battery are all on the front of the coach. The washer and dryer add about 200-250lbs to the pin weight as they are directly above it. We don't really pack heavy but the main storage is the passthrough that is directly below the nose of the coach as well as a front storage compartment below the pinbox. So the 300ish lbs of chairs/grill/metal dog fence panels etc that are below the pin on the front of the coach plus the washer/dryer being above the pin should put me well over 20% pin weight based on my rough guestimates. Again, I haven't weighed the setup but it is defintely loaded front heavy as there is no storage behind the axles. This jerking motion also happened before installing the washer/dryer into the rv.