Clutch problem

Belgian1979vette

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I had to replace my clutch but I seem to have some problems with getting it setup properly and especially the combination of release bearing free play and play in the clutch when disengaged.

The clutch in question is a Mcleod Prostreet clutch. I'm using one of their steel flywheels and a Lakewood scatter shield with block plate.

Before you question : yes I used and adjustable pivot in the bellhousing that I set to compensate for the flywheel and block plate.
The clutch fork sits at the correct angle when the release bearing is against the clutch (which is almost straight but slightly towards the transmission).

Mcleod calls for clutch 0.050" free play when disengaged and my Corvette workshop manual says to install the clutch with about .400" free play for the release bearing. When I do this the clutch will not disengage properly. When I set it less to between 1/6 and 1/4" I can get the proper air gap at the cluthc when fully disengaged, but I find it a little too close for comfort.

I'm at the end of my wits here. Any ideas ?
 
I had to replace my clutch but I seem to have some problems with getting it setup properly and especially the combination of release bearing free play and play in the clutch when disengaged.


Before you question : yes I used and adjustable pivot in the bellhousing that I set to compensate for the flywheel and block plate.
?

Been there, you might not like my suggestion, but here is what I did.

After swapping the trans at least 3 times, I cut 1/4 inch (or so) material out of the bell housing. Right at the front of the opening (towards front of car). Also threw away the rubber boot.

Speedway sells an extended flywheel bushing as the block saver moves the trans out. Don't use the roller bushing, it fails due to limited engagement (I learned the hard way).
 
I should add:

I had a Lakewood bellhousing spec'ed for a C3 big block.
Also had a adjustable ball pivot, from Lakewood I think. Most other parts were new except z bar.

My clutch was a RAM dual friction I think, but if it is important to you I can look it up. Very heavy competition clutch.

After a bunch of examination, cutting was my only solution. I thought it might only apply to my car, as the body has shifted on the frame a bit.

Tried to find the bushing on Speedway and it doesn't show up. Here is one on jeg's: Allstar Performance Long Pilot Bushing Bronze.

I never knew about these and ended up just not seating the stock bronze one as deep as possible.

Let us know your solution.
 
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Hi

I already noted that the bellhousing opening was too short, so I already cut mine, but it only helps with the movement of the TO to the back (engaged) position. It doesn't do anything for the disengaged position.
 
Hi

I already noted that the bellhousing opening was too short, so I already cut mine, but it only helps with the movement of the TO to the back (engaged) position. It doesn't do anything for the disengaged position.

Screw out the ball pivot. I made it so I could adjust the pivot without taking off the bell housing.

Also, there are two or three styles of release bearings. I had to try at least two, but I forget which worked (dimensional height).


If that still won't work you need to take more off.

Also, check all linkages for play, bent parts, and wear. Good luck!
 
Kind of pricey, but is adjustable to 3 heights. Never knew there was one.

McLeod Throwout Mechanical Bearing GM

GM Throwout Bearings

1-1/8" shaft diameter
Collar ID all lengths: 1.375"
Bearing Face all lengths: 2.640"
Short Height: 1.580"
Medium Height: 1.755"
Long Height: 1.930"



Edit: when it is all done you'll be a lot safer! Those floors (even if you have the metal inserts) won't stop much if a clutch explodes.
 
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No, that's just a cut and paste from Jegs. Contact McLeod.

Reading your issues jogged my memory, I forgot about having to try several release bearings.
 
Ok, I disconnected the rod that went to the fork still leaving the pedal rod in the current adjustment. I then pushed the TO bearing to touch the fingers and scribed a mark on the fork and bellhousing. I then reconnected and voila the TO bearing is clearly in contact with the fingers all the time when I want to have the proper airgap.

I guess I need an adjustable unit. Mcleod has these in 1.350/1.500/1.650/1.800. Going from the fact that it's now in contact and I need at least .250" free play I guess my correct height would be around 1.500"
 
That's really interesting. My car originally was an automatic, but they changed it to manual. Maybe I have a different Z-bar. hm

edit : I checked some more and it seems that all bb and sb cars after 66 have the same Z-bar with a center to center length on the link of 4 1/4" which is what I have in mine. This is what determines the stroke.

I think the only 2 things remaining are either the ball stud needs to be set differently or the release bearing needs to be of a different length.
 
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That's really interesting. My car originally was an automatic, but they changed it to manual. Maybe I have a different Z-bar. hm

edit : I checked some more and it seems that all bb and sb cars after 66 have the same Z-bar with a center to center length on the link of 4 1/4" which is what I have in mine. This is what determines the stroke.

I think the only 2 things remaining are either the ball stud needs to be set differently or the release bearing needs to be of a different length.



the "clocking" of the arms is different between pre and post `67
 
Just to update you guys :

I've ordered an adjustable throwout bearing from Novak (https://www.novak-adapt.com/knowledge/clutches-etc/) and did the math to see how long I needed to make the bearing. It still required several tries and taking the trans out in order to get close to a working setup.

On our cars you really need to get the clutch arm inside the trans as close to the trans as possible. Otherwise you will have it angled forward too much (towards the engine) and it will reduced your fork travel and effort and it will require you to put the bearing dangerously close to the clutch diafragm in order to get the clutch to release properly. This mostly will put the bearing in contact with the fingers and will make it fail in short order. This is what probably happened to mine.

There are basically 2 things that you can use to get the angle correct:
- the clutch pivot ball
- the lenght of the throwout bearing.

Both basically accomplish the same thing, but making the pivot ball longer, makes the arm touch the bellhousing (especially on my lakewood scattershield).
Lengtening the bearing is the correct way. I needed to lengthen mine to 1.650". The bearing that came with the clutch kit was the shortest possible, being 1.225". No wonder I had issues when just using it as is.

The difference lies in the so called 'clutch hat height' or the height of the diafragm fingers. This is not the same in all clutches. For example the Mcleod I'm using has far less of an angle.

When doing the math according to the Novak recommendations, you need to measure the hat height from the block rear face. (see website).

One other thing I found out is that no matter how well you set it up in terms of linkage and clutch fork angle, with the stock (as per workshop) recommendations on clutch free play, you'll only be able to get about .030 clutch plate total air gap. The Mcleod specifies .050" in their instructions, but you'll be only able to get there if you reduce your throwout bearing free play to something like .0100" which is too little in my opinion. With .030 air gap, the clutch frees up fine so far.

The problem on our cars is that the stroke of the fork is limited, so unless you start to modify the Z-bar nothing's going to change that.
 
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