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.