Help Needed: Thumping Noise from Rear Wheel

[ernie d]

Hi everyone

Noticed just this past weekend (at Detroit's famous Woodward Dream Cruise) that my 69 coupe has developed a bad thumping noise from what I think is left rear wheel. The noise changes with vehicle speed.

When I removed the LR tire, and manually turn the wheel spindle, it rotates fairly freely except for two rough spots about 180 degrees of rotation apart. At these two places, the effort required to turn the spindle goes up considerably.

What does this sound like to you........U-joint problem in the axle driveshaft?

Would appreciate any insight you can offer!

Thanks

Ernie
69CVETT

 

[The73vetteman]

I think I may have seen your car up on woodward - around Birmingham - it's a real beaut.
I don't know much about the posi rear differential, but I didn't think you could rotate the rear wheels at all unless both were in the air. If yours is rotating freely I'm afraid that doesn't sound right to me.

Anyone care to correct me on this?
'73

 

[GTR1999]

Check the tire,ujoints,and PB. Jack up both rear wheels and use your jack under the trailing arm to level it to ride height, then rotate by hand to see where the problem may be. If you have to remove the 1/2 shaft and rotate the tire to see how the bearings feel.

 

[Stallion]

How easy is it to remove the half shaft, coupeman?

 

[zackm58941]

Hi, bad wheel bearings will start making a rumbling noise before they get real bad. If you dont have any vibration problems I would check these first. You can check them buy jacking up the rear of the car and by grabbing the top front of the tire and the backside of the bottom of the tire (push and pull back from both sides), see if you feel any play. If so then its time to replace your wheel bearings. Make sure you crack both your doors before jacking on the car, C3 bodies flex a lot and you could do damage to fiberglass body parts. Good luck, let us know what you find.

 

[JohnZ]

Thumping that varies with speed is most likely a bad half-shaft U-joint; bearings make a continuous noise when they start going south.

 

[chevyaddict]

Perhaps its those squirrels making noise asking for a rest!

Just kidding...

I agree with the u-joint diagnosis..... this is a problem I had in the past and replacing them cleared it right up!

 

[81 Corvette]

I'm with the u joint theory....Mine was making some horrible thumping sounds also...jacked up the rear, pushed on the half shaft and it had about 3/8in of vertical play in the joint.

 

[ernie d]

OK team, it does indeed appear that those of us on the axle shaft U-joint path are looking good. I just removed left rear shaft and outboard joint is EXTREMELY stiff, rough and notchy to turn. I'm going to buy both joints for both sides tomorrow and install 2morrow night. Will post confirmation note on results of test drive after that.


Thanks!

Ernie

 

[JohnZ]

Be VERY careful with the outboard joints - it's easy to distort the ears on the spindle flange side of the joint when pressing unless you use the proper tool or bolt a spare flange to it for reinforcement; if you bend one, it's history, and they're $100 each.

 

[Culprit]

$100?! I got a new flange for about $41 - either Zip or Ecklers - Zip I think. Of course when I bought the new flange, I also got the tool so that I wouldn't be ordering a second new flange.

The 'tool' is nothing more than an aluminum plate with threaded holes and a circular groove milled into it. Well worth the money if you don't have the tooling to make one yourself.

Stallion - the halfshafts aren't hard to remove - just 4 bolts on the inboard and outboard ends. It really helps if your parking brake works so you can lock the shafts in place while braking the bolts loose, and while re-torquing them.

Semper Fidelis,
Culprit

 

[chevyaddict]

Also, don't forget to reinstall them the same way they came out. They are balanced and if I'm correct they were originally balanced on the car. If you put them in 180 degrees off you might get some shimmying and vibration!

 

[Vettehead Mikey]

Also, don't forget to reinstall them the same way they came out. They are balanced and if I'm correct they were originally balanced on the car. If you put them in 180 degrees off you might get some shimmying and vibration!

Half shafts were not balanced at the factory, only the main drive shaft.

 

[SR'71]

I hit a pot hole and broke the driverside 1/2 shaft years ago. Upon replacing it, I found that the universal joints were BOUND. Meaning that if the tire goes airborne the universal joints on the 1/2 shaft will break. They cant flex a full wheel turn with the wheel off the ground. I have a '71 and had to lower the car back to the ground to install the last bolt when replacing my broken out board universal on the shaft.

 

[ernie d]

Just to close this out, it was indeed the outboard U-Joint. No more thumpin' rear wheel noise!

Thanks for everyone's input

Ernie


:cool