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 appreciated
v/r
Mike P.

 

Duplicate post.

Moderators please remove.

 

Hopefully someone more knowledgeable will respond, but I believe you should NEVER put a C3 in gear while the suspension is drooping.

 

You have to jack up the trailing arms or the u joints will bind.