Intermitted Low Humming/Vibration

[gmenor]

I posted this a while back and since then had the beast checked out twice. The entire suspension system was checked out and is still solid. No codes set. Torque converter is working fine. The exhaust pipes due come close (5/8 inch) to a cross member but no rub spot on exhaust or cross member. Tires were suspected to be the culprit (slightly cupped) but now can be ruled out. I made a run up I-95 (47 miles) with no problem but coming back the humming and vibration was definitely there. This only occurs at speeds over 65 mph and all guages read normal. Under any slight pressure on the gas petal the vibration and humming can be heard and felt (it sounds like it is coming from the right side). Put on the cruise control and results were the same. At any slight change of elevation going up hill I would have let off on the gas due to the vibration and humming. Once off the interstate under hard acceleration up to 55 mph - nothing. Has anyone had anything similar to what I am describing?

[Robyn]

Very hard to say.

Every rig has its peculiaraties and what you describe, without actually hearing and feeling it in person is almost impossible to pinpoint.

This could be a harmonic setting up in the body or a vibration related to tires ???//

Try swapping the tires front to back and see if it changes.

My burb has a sound/Vibe that comes and goes at speed and its elusive.

Drivelines can also cause noise and vibes so you may want to inspect this area.

Even if there is no blatant issue presenting itself, you could have a ujoint on its way south.

Have you checked wheel bearings??

Now the airbox on the diesel can and does under some conditions maike a resonating drone.

Make sure the mountings are in good order and that all the connections are tight.

The air tube that runs down the RH inner fender could possibly have some critter living in it or it may be vibrating in the fender.

Time and miles can cause all sorts of things to happen.

As I mentioned, without feeling and hearing it, it's a tough call.

Usually mechanical things that are in the process of failing will m ake a noise throughout the operating speed range.

A noise that is present at cruising only and goes away upon hard excelleration or slight change in speed will be related to some sort of harmonic or sympathetic vibration.

Another area to check is the serp belt drive on the front of the engine.

Make sure that there is not an issue with the idler, the vacuum pump or any other accessory item (bearings failing)

The vibration dampener on the crank as well as the rubber mounted serp drive lower pulley can give issue and could possibly casue issue.

Will the noise remain if the trans is shifted into Neutral (chassis speed related only) or can you get the noise to come in with the rig siitng still and the engine at speed ???

This could possibly be a harmonic gremlin that is yours to keep.

The muffler and exhaust system could be seeing an RPM/Road speed and chassis related harmonic too..

Just too much stuff on these rigs that CAN make noise when conditions are just right.

Process of elimination at this point.

Just eliminate things like tires, bearings and failing mechanical parts then move to items that can vibrate/resonate.

************************************************** *****************
***Just read your Sig***

AFE AIR BOX??? does this unit suck air from outside??
These diesels can and do make a HELLUVA LOT of air inlet noise that at speed can produce some very undesireable noise and depending can set up sympathetic harmonics
************************************************** *****************

Check it out and let us know more

Robyn

[gmenor]

Thanks Robyn,
As for the AFE Airbox does get it's air from the existing hole where air tube was. It isolates the air filter from the engine compartment. As for the driveline - bearings and U-Joint was replaced recently and was checked again. Tires were rotated on the last oil change problem still persist intermittently. As for harmonic balancer - it is a fluidamper. I'll check everything the serpentine belt touches to see if that is the problem. Thanks again Robyn.

[DaveBr]

Did this annoying vibration start before or after you had the U-joints changed?

[Burning Oil]

I think its your PMD:D




Could be shocks of all things. I had a bad vibration in the rear and kept having the tires rebalanced. It turned out to be the shocks were basicaly froze up and instead of shock absorbing they were shock transmitting. They did not make any noise, but a vibration of any kind makes sound, its just can you hear it or not.
Plus with cupped tires it could point to shocks also.

[gmenor]

The U-joints were changed hoping that was the problem. As for the shocks they are Bilsteins change about a year ago. Shocks were replaced because of the excess sway. Both had little had very little cause and effect on the vibration/humming. This problem again is intermittent comes and goes. I can make a run up I-95 couple times and everything is good, then out of the blue it comes back. This problem was posted a while back and I kind of just rode it out. I've got time now to try and figure it why this gremlin will not go away. Some of Robyn's suggestion I will check into. Thanks for your input.

[suburbanK-2500HD]

Hi

i had a similar problem, and i changed the upper swaybar bushings.
they wasnt defect, but soft. i installed new ones and it was better, but not gone.
then i checked the u joints, could not feel any play when mounted at the truck.
when i removed it and checked, i wasnt any play, but they where moving uneven. replaced them and didnt get any worse....
Still have some vibrations now and then, but its not getting any worse.
I wonder if its to be like this.?
Maybe it depends one tire type, condition of bushings, and so on.
Everything wears and cause play, and vibrations...

[gmenor]

The vibration and humming is so bad that I have slowly build up speed. The mechanic I take my truck to is very familiar with my truck. He went over the drive line and suspension and could not find anything wrong. I have spent some time looking and relooking at what could cause the problem. All guages indicate normal operation even when the humming and vibration occurs.

[rameye]

Robin suggested throwing your rig into neutral when you encounter the vibration....if it goes away or stays will cut your possibilities in half ...try it first.

[gmenor]

I've printed out what Robyn had written and plan to do that. Problem with this gremlin is that, it does not want to act up when you want it to. Just a thought, it seems that this problem did not really surface untill I started using Rotella Synthetic couple years back. I maybe off on a year of when I started using synthetic oil. Anyhow the last time it did occurred was it was bad enough to baby it up to 70 mph and to maintain that speed.

[gmenor]

Took the beast out for a test run and the vibration and humming was in full force. At 70 mph drop it into neutral no vibration. I did notice that under head winds that the vibration does get worst. The vibration is coming from the right front. Pop the hood and relooked at the turbo and the AFE Stage 2 air fliter housing. That is when I noticed the rubber soft seal is imprinted on the insulation of the hood. Where the reinforcing cross member of the hood meets the air filter housing it get really tight. I cut out a 1/4 inch from the air filter housing where the cross member meet and did not noticed any significant changes. But I believe this is the cause of the problem. Cut out a little more tomorrow and cross my fingers. Thanks everyone

[Burning Oil]

I think its your PMD:D




.

Hey atleast my guess had you under the hood, NOT.

Could have been a long time figuring that one out.

[gmenor]

No Joy, problem still persist. Back to the drawing board. I checked again by dropping into neutral twice no vibration.

[merlot566jka]

Motor mounts?

Maybe something is touching the chassis somewhere cause a bit of noise to transfer through to the cab. By your description it sounds like its load and speed dependent. Putting it in neutral just eliminates the trans from the equation. But also when its thrown into neutral the engine no longer has a load on it and if its bad motor mounts, the engine will shift back to its resting position and not make the noise.

Check everything that can shift with the engine, especially the exhaust. It may be rubbing in a place where you cannot see. Check all of the hangers too.

hope this helps a little.