Unknown vibration

Hello,

I hope someone here can help me, or point me in the right direction.

I have a 1990 chevrolet pickup, C-1500 2 wheel drive with a 350. It has about 190K miles.

About two weeks ago I noticed a slight vibration. So I figured I might as well get the tires balanced and have them check the bearings. That was done and the bearings are fine. The guy did say the ball joint need to be replaced and that might be where I feel the vibration from.

However, last week the vibration has become worse. Now I get a pretty strong vibration when accelerating. I let off the gas and the truck just rolls along nicely, with no vibration and is quiet. But as soon as I accelerate I get the vibration back. This is at just about all speeds except below 20 MPH and at about 55 MPH it seems not as bad, but its still there.

I checked the drive shaft and the joints and they look OK.

I would appreciate any help!!

Thanks alot guys!

Check:

Tires. One could be coming apart.
Rear axle bearings. Wear in the rear axle bearings can cause all sorts of weirdness, from noise to locked drum brakes and things in between.
Rear axle - pinion, ring, carrier or any combination of the preceeding.
Shock absorbers.
Control arm bushings, both front end and rear end, upper and lower.

The tire balance should rule out anything tire related. A ball joint could practically fall out and not cause what you got there. I would look at something that happens under a load condition, check the engine and transmission mounts. Drop the inspection pan and make sure that your torque convertor is tight. Take another look at the u-joints, any sign of rust means that they are coming apart. Make sure that the counterweight on the end of the driveshaft had not come off. Jack the rear end up, check for excessive play in the pinion, there should be almost none, it will be obvious if it is bad.

Bob

Thanks!!

I will check those things out tommorow and come back here to let you know what I found.

Thanks again, I really appreciate it!

Another thought, does your truck have a center hanger bearing for the drive shaft? It would be on a 2-piece shaft only and when those let go they're spectacular. Look at your fan too, check for a loose, missing or bent fan blade.

Bob

i think bobs got you on the right track good luck...

Well, it was the rear U-joint! It had to be a molded retainer ring too! But I got it off and replaced it! Rust is not a substitute for needle bearings :)


thanks guys!!!