C2 loud knock/tick from rear

[Erik H.]

We finally got a decent spring day in the Northeast, and I took the '63 out for a quick loop. On deceleration on any road surface, I am hearing a *loud* ticking/rattle sound from the rear. It's hard to describe sounds, but imaging putting a thick piece of cardboard in the moving blades of a ceiling fan. It doesn't occur on acceleration, but as soon as I'm off the gas it's there. Any ideas?

[Dick W.]

Re: C2 loud knock/tick from rear

Suggest that you check the clearance on the exhaust system.

[Erik H.]

Re: C2 loud knock/tick from rear

Thanks Dick - went out to the garage and looked the exhaust system over on the lift. It has good clearance from the manifolds to the tips, and I shook it around a bit and everything's tight. I don't think that's what it is.

The speed of the rattle/knock is in direct proportion to the speed of the car when I get off the gas - eg the faster the car is traveling the faster the knock, and as the car slows down the knock slows as well (and actually gets louder at slower speeds). It's loud enough that someone standing on the sidewalk would clearly hear the noise from the car in the road. It's gotta be tied to something rotational.

[Edward J.]

Re: C2 loud knock/tick from rear

Erik, Did you check and see if it is a RPM sensative with the transmisson in neutral? If not maybe you may have to pick-up car one wheel at a time and spin the wheel and see if you can duplicate. possibly a drive shaft or half shaft u-joint issue?

[Tom P.]

Re: C2 loud knock/tick from rear

Had a similar situation several years ago with my 63. Loud rear banging on deceleration.

One of the half shaft universals was going away and allowing enough play in the half shaft on deceleration to contact the differential.

NOT to be ignored. The noise is not deadly but the universal may be close to failure to allow that much play. Then a flatbed ride is in your future. (Ask me how I know!!)

[Wayne W.]

Re: C2 loud knock/tick from rear

Check the snubber and bushings.

[Erik H.]

Re: C2 loud knock/tick from rear

Had the car out today for the second time this year (just lousy driving weather in the Northeast so far this Spring). I heard the loud noise on deceleration again, and noticed that I could sometimes, but not always, modulate it by pushing the clutch in and out. I drove on a long empty road with the door open to listen to the noise, and it sounded like it was coming from the middle of the car under the rear of the door. Got it home and up on the lift. One of the axis on the front u-joint has about 1/8 inch play in it. I'm pretty sure this may be the cause, and I'm going after it first. Amazing to me how car that just completed a 3 year resto and has less than 100 miles on it develops a bad U-joint!

[Tracy C.]

Re: C2 loud knock/tick from rear

.... Amazing to me how car that just completed a 3 year resto and has less than 100 miles on it develops a bad U-joint!

Eric, If the U-bolts that retain the U-joint are over tightened, the U-joint will not live very long at all. Follow your shop manual instructions.

tc