Vibration Diagnosis

**43crB** · 08.11.2011

Have a 2006 sterling with 300K miles. Cannot figure out where the vibration is coming from. It vibrates in the steering wheel, floor boards, mirrors, doors, and shifter. It is not a violent vibration but is very rapid and feels almost like a hum in the steering wheel. It seems to get worse when acceleration into higher rpm's and going uphill under load. At 55mph and above and depending on the road, the mirrors become a blur. The shop has installed new drive line and yoke, 3 point alignment, turbo, had steer tires checked for correct roundness. I think i can feel it at idle but gets allot worse once on the road. What is causing it. Is there a specialist shop in Seattle that can diagnose this problem? How can I tell if it is a worn out motor mount and would this cause this vibration problem. All suggestions welcome.

**dave26027** · 08.11.2011

Are your cab mounts tight? There are rubber cushions under the mounts in the front and they get compressed and worn down with age. Sometimes the bolts are tight but the cushions let the cab move up and down just enough to vibrate just like you're describing. I'm not familiar with Sterling- if your cab's air ride, you've got the two solid mounts in the front. If the cab's solid mounted there should be four mounts.

And this is a long shot, but if it's an air ride cab do you still have the original cab shocks on it? Might be time to replace them.

**Kittyfoot** · 08.12.2011

1. It may not be the truck..... says you're an ex-driver and your blood/coffee balance might be getting low. I keep mine at 60% dark roast.

2. Get rid of the Stirling and get an actual truck.

3. Check engine and trans mounts.

**josh.c** · 08.13.2011

You say you can feel it at an idle? Does it change if you push in the clutch? They can cause that kind of vibration. It potentially could also be the crank balancer.

**Mr. PlumCrazy** · 08.13.2011

Originally Posted by josh.c

You say you can feel it at an idle? Does it change if you push in the clutch? They can cause that kind of vibration. It potentially could also be the crank balancer.

This is what it sound like to me also
But if you shut the engine off and still feel it resort to what kittyfoot said

Originally Posted by Kittyfoot

1. It may not be the truck..... says you're an ex-driver and your blood/coffee balance might be getting low. I keep mine at 60% dark roast.

**Onetruckpony** · 08.13.2011

When they did the shaft work they may have not put it back correctly.
U joints need to be "in phase" or it will cause the type of vibration you described.
Hard to describe but look at the shaft, if the front joint is say yoke of shaft top and bottom the rest should be the same.
Any decent shop should be able to look at it and tell you in a second if it is wrong.
If it did not do this before the shaft work I would start there.
If this is good, they got something else wrong....yoke not square etc, but I would bet money the trouble is with the driveshaft.
Good luck, let us know what you find.

**43crB** · 08.13.2011

Thanks for your reply's. I am in the process of checking out these recommendations. I have to tell you how frustrating it is and aggravating to have to deal with this problem. I have 30 years driving experience and have never ran into this problem. My company is sending up older model sterlings from calif. and taking ours back there because they can pass the emissions standards in cali. If they can't get it fixed soon I will refuse to drive it. Cannot concentrate on driving because my mind is becoming fixated on the vibration problem. Thanks all. I will report back.