Persistent vibration, 87 5KQT

[Doyt W. Echelberger]

Ok, how many ways are you aware of this vibration? "low pitched, humming, 
noise" implies just using the ears. You probably also have input from your 
sense of touch on the steering wheel and in the seat of your pants, which 
you are leaving out of the description.

Steering wheel  vs Seat of Pants might help target front end vs rear end 
components.

Does it sound different with the windows down? On very smooth pavement?

What are the tire pressures? Any big changes when you raise the pressure by 
5 pounds?

Are all the tires the same?

How are the ball joints and tie rod ends? (well worn, high mileage)

Might be a combination of marginal components....complicated.

Doyt

 >>>>>>>>>>>>>>>
At 09:41 PM 10/30/2010, you wrote:
>I'm about at the end of my rope.  I have a customer's well worn, high
>mileage, 5KTQ here that has developed a low pitched humming vibration at
>freeway speeds, although the noise persists as low as 30MPH, maybe even
>lower.  I've checked the axle shafts for bends, replaced a bent RR
>wheel, and aligned the driveshaft with a cool home made fixture.  I
>spoke with a chassis and alignment guy this afternoon (he's gonna drive
>it Monday) and he asked about the wheel bearings.  I've done probably
>500 double row wheel bearings in my career, and I've never had one sound
>like this.  They mostly howl or make a low frequency rumble, and usually
>(but not always) change tone or volume when side loaded by turning the
>car one direction or the other.  This noise comes on as you build speed
>on the freeway, and is there whether you're going straight or turning.
>The volume, tone, and frequency appear to remain pretty constant.  As
>always, any and all constructive input would be sincerely appreciated!
>
>TIA!  John
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