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'99 Burb Vibration - I'm stumped!!!

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'99 Burb Vibration - I'm stumped!!!

Old 10-25-2006, 10:04 AM
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Default Re: '99 Burb Vibration - I'm stumped!!!

BTW, after you balance the drums, mark the drums using one specific lug stud so if you ever remove the drums they can be relocated using the specific stud for orientation. I stamped the drum with an X and stamped the end of the locating stud with an X as well. I pity the soul that gets the truck after you and doesn't know this.........

JH
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Old 10-25-2006, 03:13 PM
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Default Re: '99 Burb Vibration - I'm stumped!!!

Have you confirmed the balance weight is still on the flexplate? 454's of that vintage were externally balanced. Those weights can come off. The flexplate could be cracked as well.

Try your lifted/wheels-off vibration test with the rear axle on sturdy set of stands. If it still vibrates, get a big screwdriver (one that's at least 18" and hefty) Put the handle to your ear and start probing from the axle ends forward. Be VERY careful of the driveshaft- wear short sleeves and stay WAY AWAY. Try all over the axle & diff, TC and trans, then forward. The closer you get to the vibration, the louder it will be. You'll probably need an earplug for the other ear. The safest way to do this is on a lift with full-height stands.

I've also seen cracked driveshafts that vibrated and also popped and banged- you couldn't see anything externally. I have a 2-door Tahoe that my son drives now- goes thru a driveshaft every 60K.
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Old 10-25-2006, 03:29 PM
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Default Re: '99 Burb Vibration - I'm stumped!!!

Chris,
Flexplate?? Not sure what that is. If you're referring to the flywheel, I replaced that with a new GM unit. No change.

As for listening for vibrations, we actually hooked up a multi-channel accoustical meter. Several sensors (clips) were attached at the outer ends of the axle, inner by differential, pinion and back plate of differential. We noticed no appreciable sound difference, everything just "whirred" nicely and equally.

I appreciate the input, keep it coming please.

Dave
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Old 10-25-2006, 06:07 PM
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Default Re: '99 Burb Vibration - I'm stumped!!!

Originally Posted by ThirdBird
Chris,
Flexplate?? Not sure what that is. If you're referring to the flywheel, I replaced that with a new GM unit. No change.
I thought I read something about a torque convertor- led me to assume it was an auto. Manuals use flywheels, autos use flexplates. Bolts to the crank, converter bolts to it. That year 454 was externally balanced- unlike any other Chev V8 of that year. Harmonic balancer had a bob weight in it and the flexplate had a weight tack welded out before the ring gear. If the balancer was wrong, thr motor would have shaken itself apart by now. If the flexplate weight was missing (or wrong flexplate) you could get a vibration. You'd thing it would be RPM-specific, not speed-specific. On the other hand, it could be small enough a vibration to be interacting with other harmonics in the driveline.

The brakedrum suggestion is a good one. You could pull the rear brake line and plug it, then remove the drums for a test drive. The rears don't do much braking anyway. Don't do it in rush-hour traffic, though.
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Old 10-25-2006, 09:48 PM
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Default Re: '99 Burb Vibration - I'm stumped!!!

Im Hunsters friend with the 97 Burb with the mystery Vibration. Mine is fine up to 60 and over 75 mph. In between it has a constant noise/vibration. New tires didnt matter. I explained it to a mechanic, left it for 2 weeks and just got it back with new ujoints. The vibration was actually worse and after 20 miles the rear ujoint came apart and the driveshaft came off. I had it flatbeded to a different shop, the owner fixed the ujoint. He is gona drive it and check it out further. I will definatly look into the axle code and the brake balance possibities. Keep me posted and good luck with your burbration.
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Old 10-26-2006, 09:52 AM
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Default Re: '99 Burb Vibration - I'm stumped!!!

Originally Posted by area51scarab
Im Hunsters friend with the 97 Burb with the mystery Vibration. Mine is fine up to 60 and over 75 mph. In between it has a constant noise/vibration. New tires didnt matter. I explained it to a mechanic, left it for 2 weeks and just got it back with new ujoints. The vibration was actually worse and after 20 miles the rear ujoint came apart and the driveshaft came off. I had it flatbeded to a different shop, the owner fixed the ujoint. He is gona drive it and check it out further. I will definatly look into the axle code and the brake balance possibities. Keep me posted and good luck with your burbration.

Exactly why I do as much of my own maintenance/repair work as possible. Mr GoofWrench does not impress me.

"burbration"

Will keep posting with progress reports.
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Old 10-26-2006, 10:00 AM
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Default Re: '99 Burb Vibration - I'm stumped!!!

Originally Posted by Chris Sunkin
Harmonic balancer had a bob weight in it and the flexplate had a weight tack welded out before the ring gear. If the balancer was wrong, thr motor would have shaken itself apart by now. If the flexplate weight was missing (or wrong flexplate) you could get a vibration.
The brakedrum suggestion is a good one. You could pull the rear brake line and plug it, then remove the drums for a test drive. The rears don't do much braking anyway. Don't do it in rush-hour traffic, though.
I did replace the flexplate (I referred to it as a flywheel) and thought I'd discovered the problem when I removed it. There did appear to be a thrown wieght, there was a spot on the plate that looked like it had a weight welded to it at one time. Alas,,,,,,,,,,, new plate, no change.

Taking the drums off is a great suggestion!! I'll try that,,,,,,,,, in a low risk area of course.
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Old 10-26-2006, 11:28 AM
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Default Re: '99 Burb Vibration - I'm stumped!!!

i was gonna say shocks front and back the shocks gm is using are junk but when the rear brake drums were mentioned it reminded me i have a freind that had the same problem balanced the drums problem fixed i hope it is that easy for you
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Old 10-26-2006, 11:34 AM
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Default Re: '99 Burb Vibration - I'm stumped!!!

I also put KYB shocks on both my 93 and 99, made a great overall difference. Well worth the money spent.

JH
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Old 10-26-2006, 03:16 PM
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Default Re: '99 Burb Vibration - I'm stumped!!!

I think it is bent axle shafts in the rear, manifests as speed increases. Balance issues usually have certain specific speed ranges/frequencies they show up at , like 35, 52, 69 mph.

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