Diaphragm clutch..... going over center ?

[Racer57]

70 Barracuda with Tremec 3550 5 speed HP383

Trying to fine tune various things/adjustments before summer is over.  Clutch pedal has 1" free movement. If pedal isn't pressed hard onto floor, car wants to creep a very small amount.

Requires more pressure than necessary to place into 1st and and a little when going to 2nd. No grind, just pressure. Car came with diaphragm clutch and I do not feel like going to work/expense to swap it out. Seen a lot of talk about going over center if not properly set up. What exactly is going over center and what can happen ? Clutch pedal has extension welded onto it. See picture. Is the extension to prevent going over center ? Not using hydraulics and tranny is a top loader.

Seems like all I have to do is remove the extension, or at least shorten it ? I am assuming that tranny should have little to no resistance when going from neutral to 1st then 2nd.

[Dakota]

I'm no expert, but the only use of "over center" that I know of relates to the "over center" spring which, on a stock set up, reduces the effort needed to push the clutch pedal. 

What style of throwout bearing do you have? If a hydraulic throwout bearing is being used, at least one manufacturer (American Powertrain) recommends removing the over center spring to keep the bearing from being engaged with the with the clutch between shifts. 

Also for a hydraulic set up: There can are also travel limits on the master cylinder stroke (it's something like 1-1/8" for American Powertrain) to keep from damaging the master cylinder or causing the hydraulic throwout bearing to come apart from being over-extended.   If you have a hydraulic set up, maybe that's why the extension was welded to the pedal???

I don't have any experience with a stock mechanical clutch linkage set up for the throwout bearing so hopefully someone else can help you on that end if there's an adjustment needed there.

If you haven't already done so, it might be helpful to make sure the shift rods are adjusted correctly.   Here's a thread that covers this topic:
https://www.forabodiesonly.com/mopar/threads/tranny-linkage-adjustment.277279/


Might be related:  shifter rebuild
https://forum.e-bodies.org/engine-transmission-and-rear-end/4/shifter-rebuild-kit/25573/msg297021#msg297021

[Filthy Filbert]

Maybe someone did that as a pedal stop to prevent over-stroking the clutch? 

Is this a hydraulic clutch? Or direct linkage?   If it's mechanical, make sure you have it adjusted properly for clutch disc wear.   That should raise the point in pedal stroke where the clutch releases. 

If hydraulic, you may need to larger diameter master to push more fluid and get the clutch to release earlier. Or allow the pedal to stroke further

[torredcuda]

Center Force and other diaphram type clutches recommend removing the large spring on the pedal to prevent an over-center condition which causes the pedal to stick to the floor which is NOT good. I would remove the spring and cut off the homemade extension, I installed a very light spring on mine to take up the slack of the free play.

[Racer57]

No hydraulics and the tranny does not have shifter linkage. 

[Filthy Filbert]

How does your clutch not have hydraulics or mechanical linkage?   

[Chryco Psycho]

& thus I hate & never use diaphragm clutches

[torredcuda]

My Centerforce lasted 25+ years - lot`s of 1/4 mile passes, burnouts, street driving. Light pedal, never chattered, slipped, heated up etc. till it finally wore out, maybe they are not good for higher HP applications but I am very happy with mine.

[Filthy Filbert]

My Centerforce lasted 25+ years - lot`s of 1/4 mile passes, burnouts, street driving. Light pedal, never chattered, slipped, heated up etc. till it finally wore out, maybe they are not good for higher HP applications but I am very happy with mine.

I used the centerforce DF clutch on the big block dakota I built because a gentleman I knew had a built 440 that would run 10s and pull the wheels on launch, and he said he was using a regular ole centerforce dual friction.   I too never had a problem, no chatter, slips, or anything of the nature, with 530 ft lbs of torque and a 4200 lb pick up.   

[JonH]

Remove the added on piece on the pedal. It is not allowing the clutch to disengage completely. This is why you are getting "creep". If you do not see any improvement adjust your linkage to take out a little more freeplay. Just make sure that the throw out bearing is not riding on the pp. Lastly if these things do not fix your issue the clutch may just be worn out.

[Racer57]

How does your clutch not have hydraulics or mechanical linkage?

The clutch has all the linkage you expect to see. But the tranny is a Tremec and the shift mechanism is inside the tranny. Not outside.

[Filthy Filbert]

How does your clutch not have hydraulics or mechanical linkage?

The clutch has all the linkage you expect to see. But the tranny is a Tremec and the shift mechanism is inside the tranny. Not outside.

you must have misunderstood what I said then.  I wasn't talking about shifter linkage. That would have zero impact on how the clutch acts.   I was talking about the linkage for the clutch.   If it's mechanical, you have to adjust it as the clutch disc wears.  Also, if there's free play "slop" at the top of the pedal stroke, you can adjust the linkage for this as well, which will give you more effective stroke