clutch replaced on 68 (327)

[denny]

Had complete clutch replacement on my original 68. Clutch pedal goes down a couple inches before feel resistance. mechanic says this is normal . Not used to the feel of clutch pedal. He said new clutch plate 20lbs lighter etc etc. Comments please..
Denny

 

[Hib Halverson]

1/2 an inch or so of free-play is normal. Two inches is not.

 

[Hib Halverson]

Has the free-play adjustment been performed according to the Service Manual or, if the clutch is an aftermarket unit and a non-OE replacement, has the adjustment been done per the manufacturer's instructions?

Are all the clutch linkage parts in good condition?

 

[lars]

Hib is correct: The pedal free play should be adjusted to about 1/2 inch - there is specific instruction for this both in the Assembly Instruction manual (AIM) and in the Service Manual.

Check to see if there is any adjustment left on the threaded adjusting rod or if it's adjusted to the end of the rod: If it's adjusted to the end, your mechanic is telling you it's "normal" because there's nothing more he can do. Many aftermarket pressure plates have a slightly different geometry than the GM unit and require the use of an adjustable fork pivot ball set .125" taller than the stock ball. Once this is done, you can obtain normal linkage adjustment. If the stock ball was used with an aftermarket pressure plate, you may need to drop the tranny back out and install the taller ball.

Lars

 

[denny]

Sorry but I did speak to quickly! Measured amount of depression by hand and is actually 3/4in. When reaches that point it is at same level as brake pedal. Not being mechanical,my question would be, am I in an acceptable range if all else seems ok?
Thanks for replies, Denny

 

[lars]

Just check the function as follows: With the engine and tranny at operating temperature and the engine idling in neutral, depress the clutch, wait about 5-7 seconds, and then put the transmission in reverse. It should go in with no grinding. If it's grinding after more than 7 or 9 seconds of pedal depression, there is an adjustment or a range problem. 3/4" freeplay at the top is about right, but can be reduced to about 1/2" if you need more stroke to avoid grinding into reverse.

 

[denny]

I did what you suggested Lars. No grinding. I guess I'm good to go for another 43yrs.
Thanks Denny

 

[Hib Halverson]

If you have 3/4-in measured freeplay at the pedal, use the clutch linkage freeplay adjustement to decrease that to 3/8-1/2inch and you'll be set.

 

[lars]

Hib's numbers are the correct numbers. GM's intent is to have just enough free play at the top of the pedal to assure that the clutch fork is not riding on the throwout bearing when the clutch is not depressed. Any freeplay beyond a "no-touch" setting is superfluous for this objective. Adding freeplay beyond this decreases the pedal stroke and clutch disengagement, which can be detrimental to synchro life if the clutch is not fully disengaged between shifts. GM didn't add a whole lot of extra stroke to the linkage to provide a lot of tolerance on either end of the adjustment range, so proper adjustment was essential. If your clutch is fully disengaging as verified by the procedure I outlined, and the freeplay at the top assures that the fork is not riding on the bearing, you are in the range. You can use the remaining available adjustment range withing this allowable tolerance to tailor the pedal to your driving habits, keeping in mind that the "correct" adjustment is with minimal (1/2" - 3/8") "slop" at the top to assure full disengagement upon depression. Some people like a little extra (3/4") at the top to make the clutch engage a little faster coming up from the bottom, but just make sure it's fully disengaging upon full depression before doing this.
Lars