Had my 69 vette on lift to diagnosis a thumping sound I'm getting when I let out the clutch between gears and when I accelerate and de-accelerate when in the same gear. Looked for bad motor mount, manual trannie mount, rear diff mount all tight and new from frame off restoration 10 years ago. I had the vette with suspension hanging on lift, ran engine and trans to see if I could duplicate the sound while a friend was watching/listening for to noise reappear so we could pin point the problem. Once the rear wheels started spinning in gear I notice a banging sound coming from the right rear wheel. Shut vette off, rotated the right rear tire by hand to see what the noise/banging/rubbing sound was coming from that was never there before! Looks like I have outboard axle shaft U-Joint no flexing in one direction. Wheel rotates freely until it hit a certain point then the U-joint appears to bind, the swing arm moves upward to counter the bind then wheel rotates free until it hit the same point the u-joint binds again.
Question;
- Since I have my vette on a lift with suspension hanging at max down travel with wheels, am I over extending the suspension and creating this bind in my U-joint?
- If I ease/nurse the clutch between shifts I can eliminate the clunking sound, but if I accelerate/decelerate in 1-3 gears (yes its a 3 speed manual) the clunking noise is present for both actions. Could this be the u-joint making this clunking sound?
- How much of PIA is it to change out the u-joints. I'm going to attempt the half shaft removal since the under carriage/suspension parts looks brand new Zero rust/grime and bring them to a shop to press out the u-joints.
- Any tricks or techniques I should be aware of?

any assistance/advise would be greatly appreaciated
v/r
Mike P.

 

Many will say over extended. I would think the suspension sometimes goes that far in hard turns as long as shock limits travel.

this thread may help…and avoid bending flanges
https://www.corvetteforum.com/forums...anual-l82.html

 

I have seen broken u-joints and posi cases from running in the air with the suspension hanging.

 

[QUOTE=MikeP;1606830838]Had my 69 vette on lift to diagnosis a thumping sound I'm getting when I let out the clutch between gears and when I accelerate and de-accelerate when in the same gear. Looked for bad motor mount, manual trannie mount, rear diff mount all tight and new from frame off restoration 10 years ago. I had the vette with suspension hanging on lift, ran engine and trans to see if I could duplicate the sound while a friend was watching/listening for to noise reappear so we could pin point the problem. Once the rear wheels started spinning in gear I notice a banging sound coming from the right rear wheel. Shut vette off, rotated the right rear tire by hand to see what the noise/banging/rubbing sound was coming from that was never there before! Looks like I have outboard axle shaft U-Joint no flexing in one direction. Wheel rotates freely until it hit a certain point then the U-joint appears to bind, the swing arm moves upward to counter the bind then wheel rotates free until it hit the same point the u-joint binds again.
Question;
- Since I have my vette on a lift with suspension hanging at max down travel with wheels, am I over extending the suspension and creating this bind in my U-joint.

Yes, you need to raise the suspension about 1 to 1 1/2” to avoid U-joint binding

- If I ease/nurse the clutch between shifts I can eliminate the clunking sound, but if I accelerate/decelerate in 1-3 gears (yes its a 3 speed manual) the clunking noise is present for both actions. Could this be the u-joint making this clunking sound?

That sounds more like a bad snubber bushing.

- How much of PIA is it to change out the u-joints. I'm going to attempt the half shaft removal since the under carriage/suspension parts looks brand new Zero rust/grime and bring them to a shop to press out the u-joints.
- Any tricks or techniques I should be aware of?

Do not try to press the joints out of the flanges without support as you will most likely bend them. Fab up a plate to bolt the flange to before removal.

Avoid beating on the bores as that will cause issues in installing the circlips.

Buy Spicer greaseless joints. Greaseless is stronger than greaseables.

Pay close attention to circlip installation. The clip ends should lie flat against the caps. It they stick up, the clip is too thick. You may need to sand down the clips to make them thinner to achieve the correct fit.

Do not sand/grind the IDs of the shaft and flange. If you do, you risk the caps “floating” and wearing, causing issues.

When the halfshafts are out, check the play in the outer axles and check the lateral play in the inner axles.

any assistance/advise would be greatly appreaciated

 

69P88

Thanks for your reply, I didn't know never run a corvette on a lift with suspension hanging, this could/will cause binding of half shaft U-joints, but makes sense after the fact since I haven't had any issues/noises with my half shaft U-joints while driving.
Can you educate me on the snubber bushing you mentioned that might be my problem? Is it inside the differential case part of the pinion assembly? I'll do some research for video's to help understand this possible part failure/repair
Thanks again for your reply
v/r
Mike

 

this is this is

snubber i replaced 79
https://www.corvetteforum.com/forums...hing-79-a.html

 

Thanks for the pic's, I order a snubber mount kit, going to attempt the replacement. Hopefully this eliminates my clucking noise!

Mike

 

If you do need to replace.a U-joint, replace them all unless they look really new.
I just did all four on my '76, and yes, it was a bit of a PIA but if you have some fairly solid mechanical skills, you can do it.
The only thing I would caution you on is a problem I ran into.
Using a U-joint removal tool to get the joint out of the flange, I really reefed on the thing because these joints had been in place for 46 years and 129,000 miles.....and I bent the flange.
These U-joint tools are good, they can apply a lot of force, actually enough to bend something.
I'll post more details and some pictures tomorrow.
And yes, I had to get a new flange.
Oh well.