Clutch pedal jumps - help

ronstang94 · Jan 26, 2012

I just rebuilt the 302 in our 69 mustang that had sat for 20 years. Replaced the clutch and now the clutch pedal wants to jump half way through release. This causes a very jumpy take off. It just wont release smooth and easy. Ever seen this before? Any ideas what I did wrong?

horseballz · Jan 26, 2012

Loose, broken, not properly fastened motor (likely driver side) motor mount or transmission mount, or very sloppy/missing bushing on the z-bar. BTW, engine copartment looks awesome!
HTH,
Gene

2+2GT · Jan 26, 2012

Lotsa possibilities, starting with incorrect adjustment of the linkage, incrooect-sized release bearing hanging up, trashed bushings on the pedal, etc. First up I see you've used a diaphragm pressure plate instead of the OEM semi-centrifugal pressure plate. These are very different, and often the diaphragm type requires (and delivers) less pressure.

ronstang94 · Jan 26, 2012

Thanks! it was a lot of work and a lot of cans of spray! After seeing the car sit for 20 years, I cant wait to finally take it to the car show for the first time

All of the bushings are new and in the right place. Motor mounts and trans mount are new and secure. I wanted to reuse the old pressure plate, but couldn't find just the disk for sale anywhere so since I had to buy it I figured I would use it. I didn't know it was not as good as the original The pedal actually feels really stiff on the release (before to the jump), and really weak after the jump. What do you think that means?

Thanks!

gikort · Jan 26, 2012

There is a spring on the clutch pedal assembly. It is both a return and assist spring for use with the old 3 prong style pressure plates. It should be removed when using a new diaphragm pressure plate. Might solve your problem. The diaphragm pressure plate should require less foot pressure to release it and clamps the clutch more uniformly. It is better that the original.

rbohm · Jan 26, 2012

what you are experiencing is called clutch chatter. there are a number of causes, bad engine/transmission mounts, weak pressure plate springs, bad clutch disc, contaminated clutch disc, hard spots on the flywheel, excessive play in the clutch linkage, are the most common. it can also be as simple as your driving style as well, launching with too low an engine rpm while letting the clutch out a bit too quickly.

ronstang94 · Jan 26, 2012

Thanks, I will try removing the spring. I hope the new style pressure plate is better and the problem can be easily solved. I really don't want to have to pull the tranny.

I don't think "clutch shatter" has anything to do with it. What I am talking about is experienced while just sitting in the driveway with the keys in your pocket, just playing with the pedal. Driving style has not even come into play yet.

Thanks

2+2GT · Jan 27, 2012

Not necessarily better or worse, since those are value judgements. Different, though. I like the semi-centrifugal, they grip tighter as rpm increases. The diaphragm does not. The diaphragm requires less pressure to operate, so it's easier on the leg in daily driving.

ronstang94 · Jan 31, 2012

How do you remove the spring under the dash? Do you have to pull the whole pedal assembly?

Rusty67 · Feb 4, 2012

2+2 hit it. As soon as I saw that clutch, I knew it was a diaphram instead of the original style 3 finger.

The spring on the clutch pedal can be removed with the long shank of a screw driver and maybe a pair of vice grips. Just takes the proper angle.

Also, measure your throw at the clutch fork. For that type of clutch you want about 1 1/8 to 1 1/2 inches of throw.

Also, check your clutch preload. Make sure you don't have it preloaded too much or the other way around.

ronstang94 · May 30, 2012

How do you remove the clutch pedal spring?

I have been poking and prying on it while upside down in the drivers seat with the bake pedal sitting on my face... not fun. lol. I have started trying to take some things apart to get to it, but it looks like you have to take everything apart to get it out.

please help, this car has been stuck in the garage for 20 years and needs to be free!

horse sence · May 30, 2012

the 67-68 has a bolt on bracket that the spring ataches to but i am not sure about
the 69 -70 went out to check the peddals for my 69 only to find them missing sold
some parts recently and i think they made off with them,that pisses me off.as i told
them they wernt for sale.any way i agree its the pedal spring ,use caution its under pressure pedal up or pedal down. any body have a 4 speed pedal assembly for a 69??

horse sence · May 30, 2012

also make sure to put the return spring back on the throw out arm
this keeps the throw out bearing from riding on the presure plate fingers
when the pedal is up

woodsnake · May 31, 2012

In regards to the pedal return assist spring, give this a read..

http://www.mustangbarn.com/clutchspring.html

horse sence · May 31, 2012

that makes sense, you just knew there had to be an easy way that would save your front choppers. made a surprise visit on the two squirls that took my pedals,hard for them to deny,they were laying in the floor in front of there car ,invited them to never
set foot on my property again, would not have known they were missing if not for this thread

horseballz · May 31, 2012

horse sence,
Just goes to show that some dirtbags help make a good argument FOR retroactive abortion! Sad!
Gene

horse sence · May 31, 2012

horseballz said:
horse sence,
Just goes to show that some dirtbags help make a good argument FOR retroactive abortion! Sad!
Gene

the part i liked was were they tried to convince me that i gave it to them

ronstang94 · May 31, 2012

Well, Im sorry those dirtbags stole your pedals, but happy I could help!

Thanks for the link. I was finally able to get the spring out.
However, it wasn't the problem

I adjusted the clutch and the pedal feels a bit different now but still far from right.
The pedal is very hard to push down right at the beginning. And the pedal returns strong and hard right at the end of releasing the clutch, making a smooth release very hard if not impossible.

any more ideas what could cause this?

Also, with the pedal free travel adjusted to 3/4 of an inch, I am all the way at the end of the adjustment rod. Not sure if this means anything.

horse sence · May 31, 2012

sorry i wasnt able to help you but you sure helped me . Jim
does the pedal get easier to push after the stiff spot?

horse sence · Jun 1, 2012

i have been using this for some time now,replace the rod from the pedal to the z bar with a 3/8 rod threaded at both ends with 3/8 spherical heim joint ends on both ends
this will remove any friction or binding that may be occurring the pedal will feel much smoother and easier to push,this will work at the rod for the throw out arm as well . i saw a kit for this but i cant rember who had it ,but you can make it your selfe

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