I own a 2000 Pete 330 series dump truck. It has 480000 miles on it. When I get up to about 48 mph through about 60 mph the truck has a weird vibration. It's hard to describe. The wheel doesn't shake nor does it feel like anything that could be tire related. All the tires are at 100 psi as they always were. I had the rear end, and everything outside that could be checked gone over with a fine tooth comb. It's sort of a rumbling sound similar to what you experience in a 4 wheeler when you roll down the back windows. Just real irritating. When I get to 60 mph it goes away and everything is normal. It doesn't matter whether I'm empty or loaded, uphill, downhill or on flat road. My guess is that it's somewhere in the driveline. Any suggestions?

 

Have the driveline checked. I'm guessing that's where it's at. Could be a u-joint or carrier bearing.

About a month ago the wife and I had a weekend getaway in Erie, PA, which is about 3 1/2hrs away. The trip up was uneventful as well as the weekend. On the return trip - ooooo what a change. As I was getting on the interstate to head home I heard the unmistakable "squeak-squeak-squeak" sound of a bad u-joint on our Blazer. I stopped and checked it and decided to try to make it home (or at least a lot closer).

For the entire trip, the only way you knew anything was wrong was that there was a high-pitched vibration through the entire car. It was so high that it made your body tingle. You know what I mean, your ears itching, nose is tickly, etc. Anyway, we made it home ok and had it fixed the next day.

Now the side-effects: apparently this vibration really messed with both of our inner-ears. For a couple of days after getting home, we were both nauseas and off-balance. It wasn't extreme nausea, we just didn't feel "right".

Also, this constant vibration "loosened" up a bunch of crap on the Blazer. When it was in the garage for the U-joint, the mechanic noticed a bunch of other problems that didn't exist before the U-joint let go: intake gasket, transmission cooler lines (where it connected to the radiator), oil cooler lines (where it connected to the engine), thermostat was stuck open and the heater core was blocked. That weekend getaway ended up costing about $800 in repairs. It sucks too, because I still need to put a set of tires on the thing SOON since winter is basically here now.

 

Like Malaki said, check your drive shaft, U-joints, etc..

Might check your steer tires.

 

Drive line would be the first place to start looking, if that checks okay, look to your tranny and diff's for metal in the oil etc. May have a bearing going out in your diff.

 

When i drove a tri-axle, I finally traced my vibration down to a bent front driveshaft. It wasn't easy to find and had to take it to a driveline shop to have it put on a balancer. Then I traced out another vibration to the thru-shaft.

 

I have a Transfer had the same weird vib. All better now ...



So what was yours ?

 

if you have air ride. your leveling valve could be bad, or linkage broke, causing driveline to be out of alignment. wich would cause a roaring,vibrating sound. I know it happened to me.

 

I had a vibration (chatter) and took the truck in for a alignment and they checked the drive axles wheel bearings and found they were loose. Tightened them and aligned it and smooth as silk now.

 

Don't know if you've found out what it is yet. Hope so...
I was going to suggest this as well. A dump truck can be found in some areas where the ground is rough and it's possible to have driven over something that could have bent the drive shaft. A slight unbalance will not show up except at "resonant" speeds. At any other speed, it won't be noticeable. Something like bearings will be noticeable at all speeds.

 

I'm going with the drive shaft also but you might want to pay special attention to the tires and the tread depth/wear. A little different on one might be enough to cause some vibration through a speed range then as you get above that range the tire spins faster, gets slightly larger due to centrifical force and the part of tread causing the vibration is no longer in contact with the pavement and it goes away. Likewise, below that speed range more of the tread is in contact with the ground and the little part that causes the vibration is overwhelmed by the rest of the tread.
One more thing to check, and this might sound strange, is the muffler mounts. Loose mounts will send a vibration right through the frame.
Engine mounts will also. Maybe you have a compressed or worn out engine mount?
Its cheaper to check this first then go right to the driveshaft but I think thats probably where you are heading.