Bad Bad Bad...Bad Vibrations

[fallguy]

At 65mph a vibration starts from underneath.

At 70mph is quite loud (loud enough to hear) and the rear view mirror is shuddering.

It is constant and increases in volume gradually and then decreases gradually and then increases gradually and then...you get the idea.

This started after I put the new axles under it. I have had the tires balanced and rechecked by a different garage to be sure. It holds a line perfectly going down the road when I let got of the wheel.

I thought U joint, so I had a shop verify that it's the right size and it fits perfectly snug in the pinion. I thought U Joint strap but they are new too.

The driveshaft is the same from when I had the 1/2 ton axles in it.

The rear pinion angle is less than 30 degrees so that should be ok.

I'm out of ideas here fellas....help?

 

[VAL]

My truck did that also a few years back. It turned out 2 of my tires were out of balance.

 

[Mr Clean]

Were the axles new, or from a Junk Yard? could be ring and pinon not shimmed right, could be a pinion bearing, could be wheel bearings, a slip yoke on the drive shaft, and like Val said it could be a bad tire.

 

[thatcanuckguy]

from what you have listed so far, i,m betting on a bent rear axle