Highway vibration 55-65mph

[kapitein]

Hi folks,

Looking for some hints/pointers.

86 C20 454.

Drives great, many parts recently renewed... but ive got a highway speed vibration.

55-65mph got a decent vibration through the whole body of the car. Its not through the wheel or pedals, but through the body. Whole centre console is shaking (sometimes quite violently) and the chairs are bouncing left to right etc. Not the nicest thing to have and takes away from what is otherwsie a really sweet truck to drive.

Can anyone help with pointers?

Thanks

 

[TotalyHucked]

Typically through the body like you're saying means it's coming from the rear of the truck. Front end vibration you usually feel through the column/wheel and pedals.

First thing is to check wheels and tires closely. Make sure the wheels haven't slung a weight off or the tire is misshapen like a belt slipped/broke. While the back of the truck is on jack stands, put a couple lug nuts back on to keep the drums on, start it and put it in gear and go look at the axle shafts. Make sure they're not wobbling/have runout showing a bent axle.

Was the driveshaft ever out? If so, you might pull it back out, rotate it 180* and re-install.

What about motor mounts/transmission mount? Are they in good shape? If they're sagging really bad it can cause a vibration and should be replaced.

If none of those free things solve it, I'd try taking it to a tire shop that has a road-force balancer to check the wheels and tires.

 

[fast 99]

When vibrating at speed put tranny in neutral. If vibration continues would eliminate engine related issue.

 

[kapitein]

Thanks.

Im pretty sure its not the wheels and tyres, as they are almost new. However, I will get them rebalanced, just because its the easiest place to start.

Will update.

 

[edgephoto]

I am a field engineer for a major car company. I deal with vibrations all the time. Just because tires are new does not mean they are good.

Road Force is a trade name used by Hunter for radial runout of a tire. Hunter usually measures it in Pounds. The Hunter machines can be set for hundredths of an inch. Other tire equipment manufacturers measure it in inches. Think of a tire sidewall as a series of springs. The ideal tire has the same force all the way around. In reality there is a variation. If this difference is high enough you will feel it.

First thing you want to check is if you have a bent wheel. The Hunter tire equipment can measure wheel runout as well as tire runout (road force). If your wheel has a little bit of runout the machine can try and minimize the Road Force by machine the high spots and low spots. If you wheels are perfect it is a waste of time trying this.

I have gone through 10-12 tires to find 4 that have low Road Force. You can feel 15 lbs or higher. This happens with all name brand tires not just the cheap ones.

 

[Ron Sebastian]

Hi folks,

Looking for some hints/pointers.

86 C20 454.

Drives great, many parts recently renewed... but ive got a highway speed vibration.

55-65mph got a decent vibration through the whole body of the car. Its not through the wheel or pedals, but through the body. Whole centre console is shaking (sometimes quite violently) and the chairs are bouncing left to right etc. Not the nicest thing to have and takes away from what is otherwsie a really sweet truck to drive.

Can anyone help with pointers?

Thanks

I used this method to smooth out my suspension. I did this procedure before and after changing out my rear springs. Added a 4 degree shim to get a better drive shaft angle. Cup of water was smooth at speed.

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[Ron Sebastian]

This will also help you understand the importance of pinion angle.

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[AuroraGirl]

I am a field engineer for a major car company. I deal with vibrations all the time. Just because tires are new does not mean they are good.

Road Force is a trade name used by Hunter for radial runout of a tire. Hunter usually measures it in Pounds. The Hunter machines can be set for hundredths of an inch. Other tire equipment manufacturers measure it in inches. Think of a tire sidewall as a series of springs. The ideal tire has the same force all the way around. In reality there is a variation. If this difference is high enough you will feel it.

First thing you want to check is if you have a bent wheel. The Hunter tire equipment can measure wheel runout as well as tire runout (road force). If your wheel has a little bit of runout the machine can try and minimize the Road Force by machine the high spots and low spots. If you wheels are perfect it is a waste of time trying this.

I have gone through 10-12 tires to find 4 that have low Road Force. You can feel 15 lbs or higher. This happens with all name brand tires not just the cheap ones.

you can find wheel high points and low points and tire high and low with a dial indicator
But it does also kinda require having a perfect bearing to check them like a tire balancer hub (to be as minimal as possible, so the dial indicator is only reading those things)

 

[AuroraGirl]

Thanks.

Im pretty sure its not the wheels and tyres, as they are almost new. However, I will get them rebalanced, just because its the easiest place to start.

Will update.

And look at each tire, find out how much weight is put in each spot, tell or show us whats the most amoutn of weight in a spot