Vibration/resonance from rear of truck

[redrider#1]

I have seen a few discussions on this and have done a search, but could not find the info I wanted so here goes.....

At exactly 43mph(according to properly calculated Juice W/A), the rear of the truck starts to bounce up and down about 2 inches each way. This bouncing stops by 46mph and never happens at any other speed. It does not seem to be engine rpm related since I have let off throttle and let rpm's drop and vibration remains until about 41mph then it stops. Tires have been balanced 3 times, but no help. Any load in the bed of truck and vibration will tend to disappear, but I still notice it to a small degree unless it is a somewhat heavy load.

I have cranked the T-bars to level out the truck. Could this be the source of the problem? If not, what could it be?

[cowboywildbill]

Does your truck have a two piece drive shaft? If so check the carrier bearing ans Ujoints also. Are you running stock wheels? I have read post where after market wheels have been the problem. I had a vibration in another vehicle once, and we balanced the tires with no change. then I got them force tread balanced and that solved the problem. Just a couple of ideas.

[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.

[redrider#1]

Yep, found that info on frame beaming and it is exactly what mine is doing. I think that in my case the reason it is more of a problem is the 285's I mounted on the stock wheels. The tires are a little wide for the wheels and even though it still handles fine and is not dangerous in any way, I have noticed a little bounce from the rear end when unloaded especially if I try to run less than 50-55psi. I think if I put about 60-65psi in the back tires
(65 is the max) it will just about stop the beaming problem with a little sacrifice on soaking up the bumps and potholes better....oh well everything is a compromise with stuff like this and as jpblock said, it isn't really that bad, just enough to notice and wonder what is causing it.

Thanks guys.

[Mark Rinker]

Add a fuel transfer tank and keep it full...you'll never run out of fuel and the shaking will go away!

[fourtenposi]

I had a 98 chevy that had a similar problem, was at slower speeds. I took it to get a front end alignment and they could not get it to drive straight. They had it on the rack three time before they found a bent rim in the rear. I would check the runout on your rims and make sure that you dont have a bent axle or something. Have you tried to rotate the backs tires to the front to try a rule out a bent rim or bad tire issue?

[redrider#1]

I had a 98 chevy that had a similar problem, was at slower speeds. I took it to get a front end alignment and they could not get it to drive straight. They had it on the rack three time before they found a bent rim in the rear. I would check the runout on your rims and make sure that you dont have a bent axle or something. Have you tried to rotate the backs tires to the front to try a rule out a bent rim or bad tire issue?


Yes the tires have been balanced 3 times and rotated twice and they only have about 5k miles on them, but they are 285's and it it seems like I first noticed this happening only after I got these larger tires. I sure hope I don't have a bent axle or rim, but I still blame the tire/rim combo mostly.

[cowboywildbill]

It sounds like it could be the tires. If you know someone that has a stock set of wheels and tires and they would let you put them on for a test drive, then you would at least know if that is the cause or not. Sometimes these shakes and vibrations can drive you nuts because there are so many things that can give the same symptom. And it is usually something really simple that is the culprit. Let us know what you find.

[redrider#1]

It sounds like it could be the tires. If you know someone that has a stock set of wheels and tires and they would let you put them on for a test drive, then you would at least know if that is the cause or not. Sometimes these shakes and vibrations can drive you nuts because there are so many things that can give the same symptom. And it is usually something really simple that is the culprit. Let us know what you find.


These 285's mounted on stock rims seem to be wearing and handling just fine, but boy do you have to get the air pressure just right!! I tried different pressures in back and front tires until I finally came up with a combo that totally eliminated this strange vibration, frame beaming, whatever it is.....

60psi in front
65psi in rear
(65psi is max for these tires)

I think it actually rides better in all conditions so far--we shall see.......

[DriveLine98]

I just bought a 2006 2500HD. It vibrates the same way. Am I understanding that aftermarket wheels and tires will fix it? Or what's the fix here? It's drivin' me nuts! To the point I'm going to get rid of it... Let me know. Thanks in advance.

TJ

I saw some bushings online that say they help the ride of the new Chevy HD trucks... anyone tried this?

:confused:

[cowboywildbill]

Quite a while back there was a simular post on vibration, it turned out to be aftermarket wheels causing it. From what I understand, there are two basic types of wheel and hub configurations.
The type on the late model 2500/3500 Gm's the wheel fits over the hub center and the lug nuts only clamp the wheel to the hub. The hub and wheel are cut to fit each other and the hub bears the weight and centers the wheel. On the other type the wheel just sits against the hub but is not centered by it, the lug nuts center the wheel. The lug nuts have a cone shape and the wheels have a reverse shape cone cutout in them. And when tightend the lugs center the wheels and bear the wieght. Sorry to ramble, but the guy had the cone type wheels on the Gm truck. And they weren't riding true. Almost like being out of round.
As for the bushings I think you might be talking about the velvet rides. I had a set on our 02 3500. I didn't notice any real difference in the ride, but they did drop the truck down about 1 1/2 inches in the rear. That is nice for some fifth wheels that have clearence issues. But I had to move the helper spring brakets up on the frame higher so the helpers wouldn't engage too soon. Before I moved them, the truck would hit the helpers on any big bump while empty or with a light load. That seemed to defeat the purpose of the Velvet rides.

[DriveLine98]

I'll check on the hub configuration. Thanks again!

Mines not really vibrating at a certain speed, although at 45mph, it is worse than any other speed. But it does it at all speeds... even 5mph if you can believe it... The dealer told me to put some weight in the bed of the truck. But that's for the birds if you ask me... I'm looking for a fix. I have the stock rims and tires on it, so what a bummer if GM is putting trucks out on the road that sh-sh-sh-shaa k-k-k-e-e-e-e-e...=)

I'm a Chevy man through and through, by the way. But all my friends drive fords, and they don't ride like this... JMO

[cowboywildbill]

If your running the stock rims, then you don't have to worry about the hub and wheel configuration. It sounds like you might have a bent wheel or miss-balanced tire or tires. Or more likely you may have a broken cord in a tire, that could make it shake at 5 mph. I had a simular problem a couple of years ago, after a long fight with a dealer that had re-balanced my tires 180 degrees out for the weights. In other words they were put on the oppisite side of the wheels from where they should have been which made it twice as bad. I finally had the tires force balanced at a tire shop and it solved most of the problem. Later when I had new tires put on, it solved the problem totally.
I would consider going to a tire shop that has a force balance machine. That would find a broken or slipped cord also. Good luck.

[GMC D-Max]

... but I haven't been around here in a while, and came back because of this very issue.

I'm experiencing the exact same symptoms as Redrider#1, but I think it's more drivetrain related than frame related.

Just some points of reference:

Truck is a '02.
Less than 70k miles.
Bilstein shocks all around.
Torsion bars cranked, also.
Wheels are aftermarket Budnik billets, 17"x8".
Tires are recently installed BFG A/T's, 285/70-17.

The Budnik billets have been on my truck since it was about 3 months old. They were originally installed with a set of BFG M/T's, also in 285/70-17. I NEVER experienced this vibration (at the EXACT same speeds as mentioned) until shortly after I had the new BFG's installed @ around 65k miles. I've had them re-balanced twice, and they checked-out perfect both times. Whether or not the wheels are lug-centric or hub-centric is really of no consequence, because I put an indicator on the rims, with the back end off the ground, and runout is within a few thousandths of an inch. Not enough to cause the outright bounce that I'm experiencing. The tire carcasses don't appear to have any appreciable runout, either. As a test, I put the truck on short, stout jackstands (under the rear axle), fired up the truck, and dropped it in gear. This should effectively eliminate the suspension, tires/wheels, and/or frame as culprits. Low and behold, the bounce still exists, even sitting solidly on the ground. I'm thinking that it's either in the driveshaft, or the transmission. Considering how I flog on this truck (Hot Juice on higher levels, most of the time... but little towing/hauling), I'm wondering if something's giving out in the tailshaft of the transmission.

I don't buy GM's TSB about "frame beaming". I didn't experience it before, not with the stock wheel/tire combo, or with the Budnik/BFG combo. Only recently has the problem cropped up. Sounds to me like the TSB is another one of GM's "CYA" gimmicks, to give them an excuse not to spend any time on the problem. Along with their unwillingness to troubleshoot any truck with non-stock tires and wheels. What... after all these years of building trucks, are GM trucks now allergic to the aftermarket?

[cwood]

I had 285/75/16 tires on stock rims since day one on my 04 and now on my 06 but do not experience any of the vibrations described

[Fred Ficarra]

The drive shaft harmonic balancer! There is a balancer at the end of the drive shaft at the differential yoke. It's just like the ones on most all engines. That's enough mass to cause just such behavior if it's malfunctioning.

[cowboywildbill]

Good point!