C1 Clunk

[SRReality]

Ahhh! The universal sound "clunk". I have a '62, with crate 350 and M21 tranny, Hurst shifter. Sometimes, when I move out in 1st gear, I get a solid "clunk" from underneath the car, as the car "lifts" on acceleration. At times I can almost feel it "under my seat". I applied my wrench to every nut and bolt I can see, plus looked at "everything". The shocks are new and tight, the rear suspension is new and tight; the motor mounts are fine, the transmission mounts seem fine; the cross members bolts are fine. The front suspension; however, is as it was when I bought the car. It tracks well, steers "ok", doesn't wobble at any speed and I can't see anything obviously loose. I've gone over the rest of the car since I bought it, but haven't redone the front suspension yet, or the steering box. Those are on my winter project list.

Any suggestions out there? ;help

 

[Tom Bryant]

That sound usually comes from a bad u-joint. Also check your rear strut rod bushings. I doubt it is anything up front.

Tom

 

[SRReality]

That sound usually comes from a bad u-joint. Also check your rear strut rod bushings. I doubt it is anything up front.

Tom

The rear strut rod bushings are new. I replaced them myself. The noise was there before I did that and after. The u-joints appear to be new, but that doesn't mean one isn't bad. I have a tranny leak I need to deal with, so I'll check on the u-joints when I have it up in the air.

Thanks for the reply.

 

[61vette]

You might want to check your rear leaf springs. If they are weak, the springs will bow causing bumping noise. If they don"t have arch to them,they are weak. I hope this helps you. Ace

 

[Bob Willis]

Maybe the bracket that the rear spring eye is in is loose where it bolts to the frame. I think they are 3/8s bolts and I have saw the bolt threads get rusty which allows the bracket to "move" on the frame. And they are just about under your seat.

 

[SRReality]

You might want to check your rear leaf springs. If they are weak, the springs will bow causing bumping noise. If they don"t have arch to them,they are weak. I hope this helps you. Ace

Unfortunately, the springs are new. I rebuilt the whole rear suspension last year.

 

[SRReality]

Maybe the bracket that the rear spring eye is in is loose where it bolts to the frame. I think they are 3/8s bolts and I have saw the bolt threads get rusty which allows the bracket to "move" on the frame. And they are just about under your seat.

See my reply to 61Vette. I replaced both these brackets with new ones and new bolts, along with the springs, ubolts, shocks, sway bar brackets, bushings, etc.

Thanks to both of you for taking the time to reply.

 

[61vette]

I would check trans. mount closer and maybe even pinion angle. I hope this helps. Ace

 

[SRReality]

I would check trans. mount closer and maybe even pinion angle. I hope this helps. Ace

Thanks - I appreciate the thoughts. The tranny leaks, which I have narrowed down to the countershaft's "seat" in the case, so I'm going to have to pull it this winter. Therefore, I'll be getting a better look at the mounts, the cross brace, the bearings, ujoints, etc.

 

[maxphunn]

Thanks - I appreciate the thoughts. The tranny leaks, which I have narrowed down to the countershaft's "seat" in the case, so I'm going to have to pull it this winter. Therefore, I'll be getting a better look at the mounts, the cross brace, the bearings, ujoints, etc.

Maybe too much play in the differential?

 

[magoo]

I had new aftermarket motor mounts in my 62. The spacer that went over the bolt was too long so even though you couldn't tighten the motor mount bolts any more, the mount rubbers were not compressed against the engine mount. This allowed the engine to lift up under acceleration and of course clunk. I took the mounts off, took a measurement for how much to cut off the spacers and shortened them. Works fine. Just an idea.

Mike

PS: Not by chance the positraction clunking is it?

 

[SRReality]

I WISH it had positraction! Thanks for the idea. It is something for me to look at. The engine isn't stock, so the motor mounts aren't either.

Thanks for the reply!

I had new aftermarket motor mounts in my 62. The spacer that went over the bolt was too long so even though you couldn't tighten the motor mount bolts any more, the mount rubbers were not compressed against the engine mount. This allowed the engine to lift up under acceleration and of course clunk. I took the mounts off, took a measurement for how much to cut off the spacers and shortened them. Works fine. Just an idea.

Mike

PS: Not by chance the positraction clunking is it?

 

[SRReality]

I don't think so, because at times I'm convinced it's in "front of me". The differential doesn't seem to have too much play in it to me. I've rotated the rear wheels back and forth while they were off the ground and didn't get much play, or any noise.

Thanks for the thoughts!

Maybe too much play in the differential?

 

[Verle]

Since the above discussion has covered most of the drive train possibilities and given your last comment I suggest you examine your front suspension carefully.

I have heard clunk noises in front suspensions before. Something loose there is not a good thing. Check both ends of the a-frames, check the backing plate bolts and check the anchor pin, the large bolt the brake springs hook to.

 

[Silver Blue 58]

Could your front cradle assembly be loose?? Exhaust hitting frame with flexing of motor mounts?