u joint or wheel bearing ?

[mint87]

I have an 87 convertible that shakes like crazy starting about 60 MPH. After numerous tire rotations and balancing not solving the problem, I had a shop look at it. They say its the U Joints in the rear half shaft. How can you tell a bad U joint from a bad wheel bearing ? Would they have similar symptoms ? They are saying you can only get the right U joints from GM as well. Just want to make sure I'm not getting scr_wed.

 

[nyernga]

For the U-joint you can jack up the car and rotate the shaft by hand. ANY play where the shaft spins but the wheel doesn't means U-joint. I'd recommend replacing both on whichever half shaft has the problem.

I'm not sure about testing the wheel bearing but someone will chime in...

Len

 

[WNH]

Jack the car off the ground, try the 12-6 o'clock test on the wheel, if there is any play, its probably the wheel bearing.

 

[WradDad]

You don't have to get the u-joints from the Chevy dealer, but you do need to make sure you get the right Spicer part number. I found mine at a heavy equipment supply shop!

 

[jwilliams]

A bad wheel bearing will usually howl, it will also have freeplay when shaken 6-12 or 3-9 by grabbing the tire and moving it side to side. I have never seen a ride disturbance (vibration) attributed to a bad bearing. A bad u joint(s) will cause a drive line vibration and can do so in a big way. U joints like grease too, so given the age of your vette it wouldn't hurt to tear down the u joints and replace them just as preventive maintainance.

 

[WhalePirot]

A bad wheel bearing will have freeplay when shaken 6-12 or 3-9 by grabbing the tire and moving it side to side.

Isn't this best done with the caliper removed?

 

[jwilliams]

I find its best with the wheel on the hub to provide leverage. Unless the bearing is really bad it is hard to get freeplay movement with nothing on the hub. A side note, a helper to shake the wheel is useful so you can watch for things like bad tie rod ends, both inner and outer.

 

[wishuwerehere82]

I agree with JWilliams,

It's not a bad idea to get those old U-joints off the car and replaced. Wheel bearings will growl and squeal but not shake.