Clutch Adjustment issue 67 L-79

[Lawrence S.]

Today I finished installing my new Hayes clutch pressure plate throw out bearing and pilot bushing. Before installation I noticed that the new TO bearing was approximately .625 inches taller than the one that came out of the car. After installation I went to adjust the clutch and determined that I did not have enough threads on the adjustment rod to get a pedal. The only difference in the parts that came out of the car and what went into the car is the TO bearing height. The clutch fork rod on the car is 9.5 inches long. I get the suspicion the clutch fork rod is not long enough b/c of the TO bearing now being taller than what came out of the car.

Can anyone give me some insight on this? Will this hurt the transmission? I ordered a longer clutch fork rod but I will be flight judging the car soon and dont want to be called on this.

Thanks

[Bill I.]

Re: Clutch Adjustment issue 67 L-79

You got the wrong TO bearing. Bill.

[Lawrence S.]

Re: Clutch Adjustment issue 67 L-79

So you are saying the TO bearing that came in the kit was the wrong one?

[Bill I.]

Re: Clutch Adjustment issue 67 L-79

Yup, it's too tall. Bill

[Lawrence S.]

Re: Clutch Adjustment issue 67 L-79

What about the clutch and pressure plate that came with the TO bearing. Use them or take them back, or just switch out the TO bearing to the correct height one.

[Lawrence S.]

Re: Clutch Adjustment issue 67 L-79

Will the taller TO bearing hurt anything?

[Rich P.]

Re: Clutch Adjustment issue 67 L-79

OK Clutch experts help me out here and let me know if I'm on the right track. Now remember I'm dyslexic and it's working againsnt me here.

If the throw out bearing is a 1/2" taller that extra 1/2" would be on the forward face between the diaphram and the fork. IF this is correct then that extra 1/2" would put the inboard part of the fork 1/2" twards the rear of the car. That would make the out board part of the clutch fork FURTHER to the front of the car, pushing the lower rod and z-bar arm further forward. That in turn would push the upper arm of the Z bar to the rear of the car. SO why would he need a LONGER push rod, as I desribed it you would need a shorter push rod, right???

Someting does not add up. I would suspect that the clutch is also part of the problem. It seems like the diaphram geometry is different??
Where did you get the clutch from? Just because it measures the same height does not mean that the diaphram compresses at the same rate or travel as a stock one. (I learned the hard way)

Rich

[Lawrence S.]

Re: Clutch Adjustment issue 67 L-79

I got the clutch kit from NAPA.

[Lawrence S.]

Re: Clutch Adjustment issue 67 L-79

I am taking the NAPA clutch pp TO bearing out and replacing with a LUK.

[Rich P.]

Re: Clutch Adjustment issue 67 L-79

Lawrence,

post the pt # of the NAPA clutch to help those in the future to know not to use it. Also post the pt # of the LUK clutch and let us know how the adjustment is as well as what you think of the pedal pressure compared to an original. LUK's tend to be a little stiffer. I have had great success with LUK clutches.

Rich

[John H.]

Re: Clutch Adjustment issue 67 L-79

Lawrence -

Corvettes use a 1-1/4"-long throwout bearing for their bent-finger diaphragm clutches; passenger cars have flat-finger diaphragm clutches, and they use a 1-7/8"-long throwout bearing.

Also, make sure the bearing is correctly assembled to the fork; the design makes it possible to install it wrong. The ends of the flat spring on the fork go IN THE GROOVE on the bearing with the ends of the fork itself, not behind the flange at the back of the bearing.

[Lawrence S.]

Re: Clutch Adjustment issue 67 L-79

Lawrence,

post the pt # of the NAPA clutch to help those in the future to know not to use it. Also post the pt # of the LUK clutch and let us know how the adjustment is as well as what you think of the pedal pressure compared to an original. LUK's tend to be a little stiffer. I have had great success with LUK clutches.

Rich

I will do it Rich.

Thanks,

[Lawrence S.]

Re: Clutch Adjustment issue 67 L-79

Lawrence -

Corvettes use a 1-1/4"-long throwout bearing for their bent-finger diaphragm clutches; passenger cars have flat-finger diaphragm clutches, and they use a 1-7/8"-long throwout bearing.

Also, make sure the bearing is correctly assembled to the fork; the design makes it possible to install it wrong. The ends of the flat spring on the fork go IN THE GROOVE on the bearing with the ends of the fork itself, not behind the flange at the back of the bearing.

Thanks for the pictures John. That helps a ton.

Lawrence

[Lawrence S.]

Re: Clutch Adjustment issue 67 L-79

The LUK clutch kit (part number 04-21) is in the car now and everything seems to be fine. I adjusted the clutch per the Chasis Service manual, but I could not get 1.25" of free pedal travel from the rubber bumper. I replaced the rubber bumper when I restored the car and I was thinking that the repro bumper is thicker than the original? Am I suppose to measure the distance from the bumper to the part of the clutch that hits the bumper? And the distance is measured when the pressure of the pedal increases due to the clutch starting to disengage?

The NAPA clutch kit was part number MU5472-1B. This is a passenger car kit but this is what they will give you when asking for a Corvette kit. I would not recommend it. This pressure plate has the flat spring ends and the taller TO bearing.

Thanks,

Lawrence

[Bill I.]

Re: Clutch Adjustment issue 67 L-79

Glad you got it working Larry. That 1'-1/2'' is NOT really that critical. It is the distance the petal moves downward till you feel the resistance. Use you hand to push down. 1/2, 3/4 or more, you're OK. Bill