Half Shaft Height Problem

[Frank D.]

Sorting out the last few problems of my frame-off restoration. Driving to Charlotte Tuesday for Top Flight judging (God willing).

Here is a picture of my rear-end and spring set-up. Car has had a fiberglass spring and modern support rods for many years; I know, sorry.

My problem is this: with the car moving, the right side outboard half-shaft makes slight contact with the spindle flange when it turns causing a "bump" at one spot in the rotation. Spinning the wheel with the car on jack stands you can actually see the trailing arm lift as the end of the half-shaft makes contact as it comes around.

With a floor jack placed under the end of the spring lifting the whole wheel assembly, there is no contact at all, as the half-shaft rotates freely. Just had the car aligned recently and it tracks beautifully.

Unless I have re-assembled something improperly, what can I adjust to raise the level of the half-shaft slightly so that there is no contact as it turns. By the way, the left side half-shaft does not have the same problem and both half-shafts looked straight when I removed them to replace all the U-joints.

Thank you,
Frank O'Donnell
Charlottesville, VA

Hope to see you in Charlotte!

[Edward J.]

Re: Half Shaft Height Problem

Frank, with the suspension hanging on lift or jacked from the center plate under rear end everything drops and the axles do bind, Which is normal,Is there another problem that makes you suspect that its the axle shaft?

[Michael W.]

Re: Half Shaft Height Problem

It could also be that the shocks are simply too long, allowing the trailing arm to drop excessively. Most replacements cause this problem.

Unless you plan some air time with the car going over jumps, I wouldn't worry about it.

[William G.]

Re: Half Shaft Height Problem

I'm confused by what Frank stated initially.....but then for me confusion isn't difficult--especially since I don't (yet) have a C2 or C3 to go and look at. Frank says the outer end of the half shaft makes contact with the spindle flange when moving. This can't be right (read good) can it? But also the outer end of the half shaft ends in a u-joint which is in turn bolted to the spindle flange--right? So how can the half shaft contact the spindle flange? Actually the extension of the half shaft (u-joint) is always in contact with the spindle flange. Doesn't Frank mean the half shaft contacts the hub carrier (the rear portion of the trailing arm I would call a hub carrier or spindle bearing support, if you will)? If contact is made when driving that can't be right--and couldn't be caused (likely) by a too long shock.

[Timothy B.]

Re: Half Shaft Height Problem

Frank,

How high does the rear of the car sit with this spring. The only way I know to change the angle of the half shaft is to lower the car with the correct spring or longer bolts.

[Frank D.]

Re: Half Shaft Height Problem

Edward:
I understand with the car on a lift or jack stands the half-shafts will hang down where they would make contact. I suspect the half-shaft because with it removed from the side yoke and turning just the differential, there is no "bump" and the wheel turns freely.

A transmission mechanic suggested it might be a "hard spot" on the brake rotor (new), but we removed that as well, turned the spindle and the "bump" was still there. The only thing making contact and binding the turning of the spindle/wheel is the half-shaft and of course the "bump" worsens the lower the angle of the wheel assembly. Also with the half-shaft attached and the drive shaft removed (wheels slightly off the gound with a floor jack) the "bump" is still present.

Michael:
The shocks are the correct replacement from delco, painted black. They were in place before the restoration of the engine/trans/diff and there was no problems. I will re-check both shocks for the same stock# mark and measure both to see if they are the same length.

William:
I know my explanation was complicated, but from the assembly manual drawings the axle universal joint flange bolts into the spindle flange with nuts and french locks. The half-shaft can move up or down based on the angle of the wheel assembly. That is where the contact is made and it is severe enough to actually lift the controlling arm up for a second as it passes by the high spot.

I was hoping someone would maybe spot a problem with my spring/shock/strut rod re-assembly. Both sides of the spring are installed exactly in the same manner and both wheel assemblies measure the same amount of inches off the floor with both wheels removed and jack stands holding up the rear frame.

My question is what can I adjust in the rear suspension so that the half-shaft sits just high enough to clear the contact when the car is on the ground?

Thanks again,
Frank

[Frank D.]

Re: Half Shaft Height Problem

Frank,

How high does the rear of the car sit with this spring. The only way I know to change the angle of the half shaft is to lower the car with the correct spring or longer bolts.

Timothy:
Why longer bolts?
-Frank

[John H.]

Re: Half Shaft Height Problem

My question is what can I adjust in the rear suspension so that the half-shaft sits just high enough to clear the contact when the car is on the ground?

Thanks again,
Frank

Frank -

Are you saying that you have that 2-per-rev interference in the half-shaft U-joint with the car on wheels and at normal ride height? That can't happen unless the rear ride height is grossly too high (like 4 inches or more higher than spec).

Any midyear or C3 will have the interference you noted if it's on a lift with the wheels off and the trailing arms are hanging in full rebound. In that condition, you have to also jack up the trailing arms to somewhere near normal ride height in order to get free half-shaft rotation.

[Frank D.]

Re: Half Shaft Height Problem

John:
I have 1-per rev "bumps" when driving. The bump is so pronounced as to be felt through the steering column and very audible at speeds up to 15-20 mph. I'm going out for a quick test drive now and will measure the ride height front vs. rear again when I get back.

I plan on driving to Charlotte Tuesday as long as I know I won't seriously damage the car or cause an accident.

Thanks,
Frank

[Michael W.]

Re: Half Shaft Height Problem

no contact[/B] at all, as the half-shaft rotates freely. Just had the car aligned recently and it tracks beautifully.

John:
I have 1-per rev "bumps" when driving. The bump is so pronounced as to be felt through the steering column and very audible at speeds up to 15-20 mph.

I'm confused. The above seem to contradict.

Is it possible that you've got a defective front tire?

[Rich P.]

Re: Half Shaft Height Problem

If you think there is some interferance with the car driving at normal ride height then the first step would be to jack the car up. remove the rear tires and place jack stands under the strut rod spindle support joint. That way you will have the cars suspension "loaded" and will get the real world action in the drive train. Then start the car and easily put it itnto first gear and listen for the noise. If you do hear it you will be able to determine where it is coming from and figutre it out. Otherwise your are just guessing in the dark. If you don't hear the noise THEN you look into other possible causes. CAUTION YOU MUST MAKE SURE THE CAR IS CHOCKED AT THE FRONT TIRES AS WELL AS THE REAR STANDS MUST BE PROPERLY SEATED ON THE REAR SUSPENSION. I ALWAYS DO THE SHAKE TEST BEFORE CRAWLING UNDER A CAR...WHICH IS TO TRY AND MOVE THE CAR SIDE TO SIDE BACK AND FORTH AS WELL AS UP AND DOWN.

Rich

[Steve L.]

Re: Half Shaft Height Problem

place jack stands under the strut rod spindle support joint.
Rich

Rich,
Do you mean the yoke where the struts fit between?
I wouldn't have thought that was strong enough.

[Rich P.]

Re: Half Shaft Height Problem

Rich,
Do you mean the yoke where the struts fit between?
I wouldn't have thought that was strong enough.

Steve,

YEP if you look at the top of most jack stands they have a depression in the center. If you turn the jack stand so the top is perpindicular to the front to back of the car the depression or craddle of the jack stand will cup the radius end of the strut rod inbetween the spindle housing ends. I make sure that it is centerd. I have done this for almost 30 years. The reason I found this way is because when fixing the body of a corvette it must be loaded on the suspension to properly set the gaps and I would always do this with out the tires on so I had access to the wheel wells while working. It is a very safe way if you take you time in setting them up properly.

Rich

[Frank D.]

Re: Half Shaft Height Problem

Michael:

I thought of that possibility as well. I reversed the two tires on the right side and it made no difference at all., same sound, same severity. I have Western wheel knock-offs so I can't switch tires from the other side.

Frank

[Frank D.]

Re: Half Shaft Height Problem

Rich:

This was just the suggestion I was looking for. I will try that last thing today before packing the car for tomorrow's trip to Charlotte.

Thanks,
Frank