rear clunk on 68'

[greggome]

I have noticed an occasional rear end clunk when shifting gears, particularly 1st to 2nd especially if I let the clutch out quickly. If I ease out the clutch it helps eliminate the clunk. Sounds like its right rear but cant tell for sure. Thought it might behalf shaft U joints but I have read that they usually start squeaking which is a sound I have not noticed. Looked at the lower round rubber differential carrier to chassis cushion and it appears ok. U joints look like a job to replace. I hate to start tearing things apart that dont need it. Any other things that can cause that clunk that I can check?

 

[bill81vette]

Were you able to find any play(up and down in the half shafts)..
when was the last time they were greased????
I would start with that and see what happens
Half shafts/u joints are easier to get out and replace that the rear end....

Good Luck...

 

[Vettehead Mikey]

The bushing at the front of the diff is difficult to inspect in situ and is frequently the cause of the noise you describe. Start there. Don't use poly.

 

[greggome]

thanks for the suggestions. my u joints are sealed units with no grease fittings. I'll try the Diff. cushions first.

 

[greggome]

I have only been seeing poly replacements for these bushings. Why do you suggest not using poly and where can I find none poly bushings?

The bushing at the front of the diff is difficult to inspect in situ and is frequently the cause of the noise you describe. Start there. Don't use poly.

 

[Toms007]

My C4 started squeaking a little, so I checked the U-joints and they were tight, so I assumed it was something else. after a couple more weeks it continued to get worse, so I checked the U-joints again and determined that it had to be them. Once I got the half-shafts out I found there were no roller bearings left, just packed rust around what was left of the U-joint ends. Never realized how bad those could get and not really make much noise or being able to feel the looseness.

Back when I had my 64 coupe I replaced the half shaft U-joints and I really don't remember it being that big of a job.

 

[GTR1999]

Bair's should have the rubber snubber bushings.

 

[Vettehead Mikey]

I have only been seeing poly replacements for these bushings. Why do you suggest not using poly and where can I find none poly bushings?

They're manufactured incorrectly- too thick. Poly is a poor choice for most bushings anyway.

 

[Hib Halverson]

Another thing to check is the front bracket on the rear axle housing.

if the bolts loosen, the holes begin to elongate. Once the elongation starts, no amount of tightness on the bolts will hold the bracket in place. The bolts loosen and you get a clunk-clunk as you are on and off the throttle.