Clutch "knocking"?

[67fish383S]

I have what may be a stupid question, but I'm relatively new to owning a 4-speed classic. I know my way around the engine compartment, but the A-833 is a new experience for me. I bought an original 67 Barracuda Fastback 383S 4-speed a little less than a year ago. It came to me with the original trans, but the previous owner had recently installed a new McLeod diaphragm style clutch & throw-out bearing, flywheel was resurfaced, clutch linkage was rebuilt, and the shifter was upgraded to a Hurst Competition plus conversion from the original inland shifter mechanism.

I'm not sure this is a new thing, or if I've just never noticed it before, but when the engine is idling with trans in neutral and the clutch engaged, I hear what I can only describe as a very faint knocking. The sound has no regular pattern, it's just random. It almost sounds like something is loose and rattling, but not severely so. It took me quite a while to determine that it wasn't something loose on the block or an internal engine noise. When I push the clutch pedal in, the noise stops. There is also a distinct sound when I reengage the clutch when it is idling in neutral. The car drives and shifts normally.

Is this sound normal or something I should investigate? Thanks in advance.

 

[moparmat2000]

You mentioned it's a diaphragm multi finger clutch pressure plate and not a 3 finger Borg and Beck style. Check under the dash, specifically for the really really large clutch assist spring. If it's there, remove it. Not needed with a diaphragm style clutch, possibly adjust the linkage under the car as well. Should solve your problem.

If you dont want to destroy the spring and its retainer, easiest way is to remove the complete pedal assembly from that car, push the clutch pedal down. "Watch your fingers", you can actually push the pedal past it's normal floorpan stop point with it out of the car, and simply unhook the spring and its retainer and remove them.

Other people cut em off with a die grinder, or stack washers between the coils to spread the spring to unhook it. Have fun its like a giant mouse trap. Pix are of the pedal set I restored for my 67.

 

[moparmat2000]

You may want to pull it out anyway and mod the clutch pedal for a better pedal ratio by adding 3/4" to the throw. Old drag racers trick. You wont need to push the pedal very far for clutch disengagement. Circled area is the spot you lengthen. Mine has already been modded. Dont extend it over 3/4" or you can put the throw out bearing through the fingers when you put the pedal to the floor. Stock pin to pin dimension is 5&1/4" your extending it to 6" pin to pin.

 

[Daves69]

FWIW, The HD pedal has an outer bracket to deal with.........

 

[67fish383S]

You mentioned it's a diaphragm multi finger clutch pressure plate and not a 3 finger Borg and Beck style. Check under the dash, specifically for the really really large clutch assist spring. If it's there, remove it. Not needed with a diaphragm style clutch, possibly adjust the linkage under the car as well. Should solve your problem.

If you dont want to destroy the spring and its retainer, easiest way is to remove the complete pedal assembly from that car, push the clutch pedal down. "Watch your fingers", you can actually push the pedal past it's normal floorpan stop point with it out of the car, and simply unhook the spring and its retainer and remove them.

Other people cut em off with a die grinder, or stack washers between the coils to spread the spring to unhook it. Have fun its like a giant mouse trap. Pix are of the pedal set I restored for my 67.

View attachment 1715714973

FWIW, The HD pedal has an outer bracket to deal with.........
View attachment 1715715035

Thanks guys. I did confirm the spring had been removed from the pedal assembly a while back when I was having another issue with some play in the pedal assembly right after I got the car. It was missing the circlip that holds the pivot assembly together, so the pedal was moving side-to-side a bit.

I did find one thing this morning that might have been part of my problem anyway. The nut that holds the clutch linkage to the body right above the frame rail was missing, so I put one on and got that all mounted nice and tight. Not sure if it was also causing "the knock" just yet, but I know it was the source of a really annoying body squeak when it was going down the road.

I did notice after getting the linkage mounted solidly that the other end seemed to be slightly off center, or not in a perfect straight line if that makes sense (see circled area of the pic). Not sure if that is anything I should try to correct because it looks like there is supposed to be play in that joint and the linkage seems to work fine. Any thoughts on that?

 

[Daves69]

Ideally and in a perfect world, you want the Z to be straight across in any view. If the bearings and ball mount aren't worn out causing loss of motion and it is smooth in travel, that small offset, IMO, is not hurting you. It is designed to swivel some.

 

[AJ/FormS]

You may want to pull it out anyway and mod the clutch pedal for a better pedal ratio by adding 3/4" to the throw. Old drag racers trick. You wont need to push the pedal very far for clutch disengagement. Circled area is the spot you lengthen. Mine has already been modded. Dont extend it over 3/4" or you can put the throw out bearing through the fingers when you put the pedal to the floor. Stock pin to pin dimension is 5&1/4" your extending it to 6" pin to pin.

MATT; the diaphragm clutch is already easy on the leg, and departure, for street use, IMO, is already fast enough, So while I agree that what you are saying is correct;
I have to wonder if the trouble is worth it
in this case.

 

[AJ/FormS]

Any thoughts on that?

If the downrod is staying more or less in the center of the window,(side to side) throughout it's travel. AND the inboard pivot of the Z-bar is not casting off the springclip during take-off when the engine torques over,
then IMO, the alignment is close enough. See post #6

 

[moparmat2000]

It's not about making it easier on the leg, it's about increasing the pedal ratio for shortening the pedal throw to full disengagement for shifting. You dont have to press the pedal as far to disengage for shifting.

 

[67fish383S]

Fingers crossed, mounting the clutch linkage properly seems to have stopped the sound I was hearing. Small win, but at least it's a win. Thanks to all for the comments.

 

[AJ/FormS]

Fingers crossed, mounting the clutch linkage properly seems to have stopped the sound I was hearing. Small win, but at least it's a win. Thanks to all for the comments.

BTW
when you are finally motoring, you do not have to push the clutch all the way to the floor. And with a diaphragm clutch, at higher rpms, that occasionally ends with the pedal staying down there.
So, you only need to push the pedal down far enough to pull a clean shift. You can tell where that is by; with the car rolling, shift from neutral to any gear, at various pedal positions, while continuously reducing your pedal-push. At the first sign of difficulty, that's not quite enough.
The reason the car needs to be rolling is so that you don't get confused by the teeth on the synchros butting up on the slider teeth; which in first gear happens a lot..
The reason Chrysler put so much travel in the pedal, is so that you don't have to adjust the freeplay so often; AND, because in reverse, there is no synchro, so it usually requires a lil more clutch departure to shift into reverse without grinding.
If you lengthen the lever as Matt shows very nicely, you may need to put a block under your pedal to prevent over-travel, which, with a diaphragm-clutch and no rev-limiter, can end badly, when the pedal fails to return and you gas pedal is on the floor.
That happened to me and I watched helplessly as the tach crossed 8000 rpm.... on it's way back from wherever it had been..... Yeah so I ordered a rev-limiter soon after. In my case, my valve gear was set up to put up with "Some" overspeed, but I found out that day, that I'd done good, as no damage was done.
You're results may vary.

 

[65 Cuda 340]

It's not about making it easier on the leg, it's about increasing the pedal ratio for shortening the pedal throw to full disengagement for shifting. You dont have to press the pedal as far to disengage for shifting.

Or, the low tech way to limit clutch travel is bolt a block of wood to the floor under the carpet. As I recall, plate departure for a borg and beck is .080, while a diaphragm only needs .030. Or something like that.

 

[AJ/FormS]

My CenterForce likes .080 to go from neutral to first/reverse, but maybe half that afterwards, except at 7200, it likes a lil more.
I left my pedal-throw long, because it is easier to modulate in city traffic, and at parade-speed, and thru the car-show parking-lot.