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Author Topic: Vibration above 70 mph....driving me nuts  (Read 274 times)

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Motor7

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Vibration above 70 mph....driving me nuts
« on: May 1, 2019, 06:16:50 AM »

I had a initial high pitched whine which sounded like a pinion gear.  Then started getting a serious vibration when off the throttle or going down hill/coasting over 70mph...almost rumble strip bad. Had all U-joints replaced on both driveshafts with Spicers and the vibration is still there. I took it to a Chevy dealer first and they said metal in the front Dif. Took it over to an independent tranny shop and the guy gave me the same diagonals so we replaced the front Dif with a re-man.

Now I have a low pitched whine and the vibration above 70 is still there but not as bad. It's a buzz I can feel through the steering wheel and feet and it is accompanied by a low frequency noise(my hearing is shot, but I can still hear low frequency stuff better than most). Tranny guy is stumped. Dealer had replaced the RT front wheel bearing before I bought the truck, so is it possible that the left wheel bearing is causing this?

I am going to get it up on my 4 jack stands and throttle it up to see if I can isolate this vibration....it sure is hiding well. What can vibrate when it is NOT under a load in the drive-train?
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AirJunky

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Re: Vibration above 70 mph....driving me nuts
« Reply #1 on: May 1, 2019, 06:38:04 AM »

If you replaced the front diff, wouldn't the bearings be a part of that assembly?

Have you had the tire balance checked?
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Motor7

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Re: Vibration above 70 mph....driving me nuts
« Reply #2 on: May 2, 2019, 18:43:42 PM »

No, the Dif and the wheel bearings are separate. I'm going to have all 4 tires balanced, but it just makes no sense that they are out of balance when not under a load???

There is another new post with similar problems(whoops it's dated December). I have owned several 4wd Chevy trucks and never had a drivetrain issue. The Avalanche is a Suburban frame, so do the Burbs ans Tahoe's have similar issues?
« Last Edit: May 2, 2019, 18:46:32 PM by Motor7 »
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Motor7

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Re: Vibration above 70 mph....driving me nuts
« Reply #3 on: July 17, 2019, 08:54:46 AM »

Still chasing the issue. Tires rotated and balanced which was no help. Going to get it up on a lift and run it up to speed and go over it with a stethoscope next.
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Re: Vibration above 70 mph....driving me nuts
« Reply #4 on: July 17, 2019, 10:05:24 AM »

A list of things to check not in any order other then how they pop in my old mind:

Drive shaft out of balance
Drive shaft slip joint sticky or too loose.
Rear axle bearings
Front hub bearings
Cracked fly wheel
Torq converter issues
Lots of play in front or rear suspension?
Bad suspension bushings, ball joints etc.

Wheels not round, bent or damaged.
Road force balance tires  is awesome as it similates road conditions by running tire against a roller to simulate road contact and tire not round.
New or old tires, maybe belt slip or egg or something.

Something keeping wheels from mounting flat and concentric

Engine mount bad - probably not as gives you more of a clunk.





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