Recently my '79 was making a grinding noise when I would turn the steering wheel at low speeds to the right. I greased the ball joints and that noise went away. I also found out that there was a wear indicator on the lower ball joint, which seemed to show the joints were still good.

Yesterday when I was going down the highway accelerating beyond 50MPH the car began to vibrate. It's not vibrating the steering wheel, just the body of the car, and when I go below that speed it stops. I cant tell if it is shaking on one side or not, but what could be the possible causes of this?

Thanks

 

im curious to see what other people have to say about this, my 78 seems to vibrate pretty good on the highway as well. Stops as soon as i begin to slow for an off ramp

 

I'd suspect a bad u-joint,check your driveline real well.

 

Excuse my ignorance, but could you explain exactly the role the U joint is playing here, and what it could be doing that would cause vibrations at a higher speed?

 

Could be that a wheel weight fell off causing a tire to be out of balance or a busted belt in a tire.I had a car a few years ago that done this and it was the tire out of balance,i had another car that done this when the centerlink went bad so i'd say probably tire balancing or a front end component-centerlink,tie rod,etc.

 

Loose parts on a driveline which is spinning pretty fast at highway speeds can certainly cause a vibration,drivelines are balanced so they don't vibrate or wobble,when the needle bearings go bad in a u-joint making the bearing cap loose (and soon to fail) it creates enough play to cause problems at higher speeds.

 

The U joint is certainly a possibility, and you can check it easily without even getting out of the car. Just put the car in drive and give it a slight bit of gas (very slight!!!!!!) then put it in neutral and into reverse. If it "clanks" going from forward to reverse the U joints are pretty worn out.
I'd also check the wheel balance, as a slightly out of balance wheel will cause this same scenario. If it's way out of balance it will vibrate a much lower speeds.
Finally, if all those check out you will need to check all the tires and wheels for out of round. An out of round tire will also cause this vibration, or even a slightly bent rear axle. The tires will be seen when checking the balance by any good tire guy. The axle you'll need to block up the rear end on jack stands, and then put the car in gear at idle. Then just look at them turning and see if the axle is bent by the wobbling wheel and tire.

 

I'll add to this that a broken belt inside a tire can also be the culprit without being seen,it can be hard to find but as a last resort might be found checking tire balance on a spin balancer by a savvy service tech.

 

Well I found out one of my back tires was "bulging out", so I replaced both back end tires, everything balanced and rotated now the problem has stopped. So I guess is was just a tire issue, guess I got lucky this time.

 

Cool,good thing you got that tire off there before it did more than bulge.