Mysterious vibrations

2006 CHEVROLET EXPRESS
120,000 MILES • 6.0L • V8 • TURBO • 2WD • AUTOMATIC
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PETER HARWERTH
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I am experiencing vibrations similar to driving over a rumble strip. It starts occurring at around forty mph and subsides at around sixty five to seventy nine mph, re-occurring when letting off the gas.
It started "out of the blue" after a highway drive. The following has been checked/replaced so far: U-joints replaced, rear end been opened and checked for metal shavings and oil, starting up vehicle with front-side disconnected driveshaft, tires have been balanced, rear axle bearings and wheel bearings been checked, all without any result. No vibrations with disconnected driveshaft. Vibrations are still present. What to do and what could be checked next? I have already spent $600.00 without any result. Getting desperate.
Nov 5, 2016 at 9:04 AM
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HMAC300
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try moving front tires to rear and check tires for bulges may be a bad tire. also drive in a large circle like right hand then left hand then and see if you hear any loud noises. it may be a bearing problem even though they have been checked. finally have belt and tensioner checked recommended replacement for both is 60,000 miles.
Nov 5, 2016 at 10:33 AM
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PETER HARWERTH
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Hi and thanks for your answer. Sorry for the delay in getting back to you. I tried all your recommendations and there has been no result or change in vibrations. Tires have been crossed, checked re-balanced and I did the circle around test. However, I have now heard a noise from my rear brakes indicating a warped rotor, Could that produce the experienced vibrations? When braking I noticed increased vibration. Also, I see there is a lot of talk about balancing the driveshaft. I will check out whether any weight has come off of the driveshaft.
Thanks again.
Nov 9, 2016 at 12:36 PM
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HMAC300
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if the rotor is warped normally you feel a pulsation like pedal going up and down when braking. it won't move much just feels like it and truing up or turning rotors if they are within spec takes care of that with new pads. one other thing I f you have installed aftermarket tubular steps to get in and out of van check to see if they are hitting cab from frame there is a tsb out on this. causing the type of problem you have. removing them to test and see if the vibration is gone means that they are.
Nov 9, 2016 at 12:45 PM
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PETER HARWERTH
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No entry steps on this van. I cannot feel any pulsating on the brake pedal, but every time I have hit the brakes the van starts off again with this terrible scraping sound, then subsides as we accellerate. What about that driveshaft?
Nov 9, 2016 at 2:35 PM
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HMAC300
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have the brakes been checked? the scraping may be the brake pad warning signal or brakes worn out and steel hitting steel on rotors.
Nov 9, 2016 at 3:15 PM
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PETER HARWERTH
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Mechanic said he did check on them, but we need to re-check that.
Nov 9, 2016 at 4:49 PM
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STRAILER
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Can you tell if the problem is coming from the front or the rear?
Nov 12, 2016 at 12:30 PM
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PETER HARWERTH
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We are pretty sure the vibrations originate from the rear. If it would be from the front I would feel more movement in the steering wheel, I think.
Nov 12, 2016 at 1:26 PM
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HMAC300
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ifit's that from the rear then it may be a pinion bearing or some type of rear end problem if ujoints are ok and everything is in balance like brakes/tires. also vans are bad as far giving vibrations and noise from rear.
Nov 12, 2016 at 3:39 PM