Truck "Bouncing" at 40 MPH

[04duramax88]

I have tried everything I can think of so I am looking for ideas. My 04 duramax "bounces" at about 40 MPH, almost like I am going down a rough dirt road. I took it to the dealer since I am still under the extended warranty. They rebuilt the hubs but said that the pittman and a arms needed replaced. Once I got it back, it was still "bouncing". I got an alignment and they said the arms were fine.

I replaced the shocks and u joints, but I am still having the same problems. Someone suggested the driveshaft, but I had it spun and that is fine too.

I would appreciate any ideas that anyone has, cause I am stumped.

TIA!

[More Power]

Welcome to the board! Introduce yourself. Tell us more about your truck. How long have you owned it? How many and what sort of miles are on it? Has the suspension been modified? What tires are you running? What shocks?

Jim

[04duramax88]

My truck is an 04 Chevy Duramax. It has the LLY engine so I guess it is a 2004.5. I bought the truck new in 04. It has about 56K miles. These are mostly to work and back. Due to health issues, I haven't been able to play with it in the mountains for about a year.

I just put Monroe shocks on it yesterday, there is no modification to the suspension.

I am running BFG All-Terrains 265/75R16.

[Mark Rinker]

Could it be one or more tires with a tread separation? It would be easy and interesing to swap on a set of different wheels and tires to compare.

[jbplock]

One common problem I’m familiar with is called “ frame beaming” (TSB 1844688). It’s a beam shake vibration that is usually felt in the seat and occurs between 40-60 mph. Severity of the shake may vary from vehicle to vehicle. The diagnostic procedure says to place 200-500 lbs in the bed and if the shake goes away, it’s “beam shake”. The TSB further states it’s a characteristic of the vehicle and that there is no fix (for the 2500/3500HD’s).

On my 03 crew cab I get a slight bounce type vibration at approximately 45mph when the bed is unloaded.. In the winter I run with four 80lb sand bags in the bed and the vibration is gone.

[Mark Rinker]

I think an auxiliary fuel tank and an extra 60-80 gallons of fuel on board would be my plan. My 2002 definately rides betters since adding that extra weight mid-ships, although I never noticed the 'bounce' described here.

[More Power]

Could it be one or more tires with a tread separation? It would be easy and interesing to swap on a set of different wheels and tires to compare.

That's what I'd do too....

Jim

[phill0072]

I would suspect tires, but I will add I had a 98 gmc 1500 and the torsion bars became weak over time and it was bouncing when I got it above 35mph I ended up replacing the bars and bushings and the problem went away. Have you ever had a plow on the front or a heavy steel custom bumper?? they will both sag the front causing the bars to loss there tension and weakin over time causing bouncing and front end sag. or maybe one of them is lose or has a bad bushing in it

[leolkfrm]

Old school to eliminate the tires........inflate them 10lbs over max and see if it goes away

[atchafalaya_man]

I have an 02 3500 Dually that does the 'bounce' at about 45-50 mph.

It's as if the tires are out of round and are causing a jumping feeling each time they go on the high-side.

Balancing the tires, alignment didn't remove it. I run them at 80 psi, so they aren't squishing.

It DOES occur on the same section of road (a smooth asphalt interstate) so I suspect the Frame Beaming is a plausable explaination caused by just the right combination of irregular road surface. It does not occur when loaded. Thanks for the explaination.

[tufcj]

My '03 2500HD (crew cab, short bed 4x4 if that matters) does it, but only when pulling a trailer (7000 gross, about 500lb tongue weight). Right between 45-50 regardless of what gear it's in. I never feel it when empty or with a load in the bed. It's not the trailer, because I've pulled it with other trucks and it rode fine.

Bob
tufcj

[KrazyNate]

Mine does it as well, and it was amplified with some bad tires.. Went to new, higher quality, tire and the shake is now hardly a noticeable issue.. Still there however so slightly..