01 2500HD vibration between 70-80mph

[BAA]

I'm stumped.

Have an 01 6.0L 2500HD 4x4 crew cab with 120,000 miles.

Everyhting is tight and noise free until the vehicle hits 70mph. I am getting a vibration which seems to be coming from either the tranny or the trasfer case. If I speed the truck up to 80mph the vibration is gone.

When the vibration starts there is also a noise that goes with it - sounds almost like wind noise, or even an agressive tire noise.

Any ideas where to look?

Bob in MI

[fillupread]

You need to narrow it down for us.

Between 70 and 80 when it vibrates:

does it stop if you knock it in N?

does it only vibrate while on the gas?

What happens when you coast at those speeds?

While at that speed, pull it down a gear and see if the vibration speeds up or stays the same while keeping the speed at a higher RPM

Most high speed vibrations come from the tires. Try rotating them and see if the noise changes.

[BAA]

Thanks for your questions and comments

I will rotate tires and see what happens

As for your questions:
If I change the gearing (drop down) the noise/vibration stays the same - to me I cant notice the truck shifting down or the RPM increasing.
If I let off the gas the noise/vibration seems to get a little worst (at least the noise does increase).
The nosie/vibration starts at 70mph and gets worst at 75 then starts to reduce until 80 then gone (so the range of noise/vibration in between 70 and 80, with 75 being the worst)
I have not put the truck in "N" so I dont know what would happen.
Also, while the nosie/vibration is happening, there is some noise (from vibration) coming from the 4x4 select lever.

[fillupread]

I am between U-joint, tires or a torque converter shudder.

Test it a few more different ways and post what you find.

[BAA]

Ok will test the following and post results.
1. Rotate tires front to back
2. If noise still present, shift into N at 75mph when noise/vibration seems to be at it's greatest.

As for U joints - When stopped, I have shifted from drive to reverse and back again and there is no lash, play or noise in the drivetrain. Also I did get under the truck to check the drive shaft U joint and there is no free play.

[BAA]

OK, here's and update

Rotated tires - front to back, back to front

Test drive - same problem present. Shifted into N and no change in noise/vobration.

Shifted from O to 3 and no change in noise/vibration (enginer RPM did increase as expected).

Any further ideas will be appreciated

Bob in MI

[fillupread]

Originally Posted by BAA

OK, here's and update

Rotated tires - front to back, back to front

Test drive - same problem present. Shifted into N and no change in noise/vobration.

Shifted from O to 3 and no change in noise/vibration (enginer RPM did increase as expected).

Any further ideas will be appreciated

Bob in MI

OK,, knocking it in N and pulling it down a gear changed your engine and tranny speed. The vibration stays the same which means its in the final drive somewhere. That leaves you drive shaft, rear axle, wheel bearings; anything after the trans.

You said this was a 4WD, what does it do in 4Hi on the street? Any change?

Do you have a camper shell on the bed? Do you have dual exhaust? Believe it or not I got a lot of "vibration" complaints that was from exhaust enhanced by a campershell. WE used to weld or hang led weights from the exhaust to dampen the resignation.

When you rotated the tires did you check wheel bearings? The front bearings are assemblies which have a tendency to wear fast once they start to wear.

[BAA]

No camper shell on truck

Have not tried in 4H but will do

Did not check wheel bearings when rotaing tires

Exhaust is stock, single.

Will take to a local shop to see what they think.

Really appreciate the suggestions

Bob

[Rmbodie]

Sounds like a posible drive shaft out of balance or u-joint about to go bad.lay under it and see if you can move it sideways. Rob

[fillupread]

Originally Posted by Rmbodie

Sounds like a posible drive shaft out of balance or u-joint about to go bad.lay under it and see if you can move it sideways. Rob

Usually a drive shaft or U joint wont vibrate at only a 5mph window.

Usually when you have a vibration that is in such a tight window its comes from a 'harmonic vibration' . Basically something is putting out a frequency from vibration that only effects the vehicle at a certain wave length.

Sounds crazy but this is what made all the import cars dash hop in the 80's and early 90's at particular speeds.

I would start to lean toward an out of balance drive shaft by now (even though it isnt typical for one to cause a problem in such a small window) Next time your under your truck check the u joints well and see if you have any weld marks with no weights on the drive shaft (might have thrown one). There are two different kinds of drive shafts on Silverados. More than likely you have a two piece with a center support bearing. Check that center bearing too. Look the drive shaft over for dents or dings.

[BAA]

I was doing a search and it seems like someone had the same problem in 2004 as I do now.

No final outcome is stated, I will contact the poster to see what was found to resolve.

http://www.automotiveforums.com/vbul...t=70mph+2500hd

[masapell]

Originally Posted by fillupread

Usually when you have a vibration that is in such a tight window its comes from a 'harmonic vibration' . Basically something is putting out a frequency from vibration that only effects the vehicle at a certain wave length.

What would cause a harmonic vibration, in that 5mph window. I occasionally have that in cooler weather. I know it is harmonic, as it is the same frequency. I have put the truck on jack stands and heard it humming in the frame, but could not pinpoint the source. I have often thought it is something related to the transmission.

Sincerely,
Matt

[intel_guy]

Couldn't it be wheel alignment or tire balancing? I have a similar issue AFTER rotating tires today. I'm going to get balanced and aligned and see what I find. Will post tomorrow.

[BAA]

Just wanted to add a comment after checking more that the vibration/noise seems in part to be coming from the 4x4 manual shift lever. I can feel the vibration if I hold the 4x4 shift lever. I did come across a post of a procedure to install a foam washer in the transfer case to eliminate a rattle, the PIP number of PIP3156A.

Also, my truck has a 1 piece drive shaft

[weo38]

There is a TSB out for frame "beaming" at a certain speed range this could be what you are feeling. The TSB says it more common in HD models than non HD models. It basically says there is a harmonic resonance through the frame and is felt in the cab. I have the same vibration only between 40 and 50 with 45 being the worst spot. Hope this sheds some light on the situation.