Clutch adjustment - Pontiac GTO Forum
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post #1 of 4 (permalink) Old 08-17-2018, 10:50 AM Thread Starter
 
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Clutch adjustment

So I swapped my 455 out for a 428 and everything is set except for the clutch. Looking in my restoration book it says to remove the lash at the clutch with the clutch pedal at the stop. It then says to turn the adjustment rod 3 1/2 + - 1/4. Is the lash between the rod and fork or the release bearing? I have tightened the rod until the point is seated into the fork with no movement back and forth. I then turned it 3 1/2 turns further into the fork which made it pretty tight to turn by hand. I could’ve turned it maybe another 1/2 to 3/4 by hand and that would’ve been it. Is that the correct way to set it?
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post #2 of 4 (permalink) Old 08-17-2018, 07:21 PM
 
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Originally Posted by Ohio66GTO View Post
So I swapped my 455 out for a 428 and everything is set except for the clutch. Looking in my restoration book it says to remove the lash at the clutch with the clutch pedal at the stop. It then says to turn the adjustment rod 3 1/2 + - 1/4. Is the lash between the rod and fork or the release bearing? I have tightened the rod until the point is seated into the fork with no movement back and forth. I then turned it 3 1/2 turns further into the fork which made it pretty tight to turn by hand. I couldíve turned it maybe another 1/2 to 3/4 by hand and that wouldíve been it. Is that the correct way to set it?
Never used any book specs to adjust my clutch linkage. Just make sure the pedal is up against the rubber stop under the dash, ie clutch pedal fully released.

Position the clutch fork so it's about 1/4" from the bell housing opening and then turn the adjusting rod out until it seats into the clutch fork cup. There is a spring that hooks to the linkage and holds the rod into the clutch fork cup, not adjustment pressure.

You want some play in the clutch fork. You do not want the clutch fork up against the bell housing. You don't want a large gap between the clutch fork and bell housing opening - which typically indicates too short of a throw out bearing. You don't want the clutch fork being forced into the side/opening of the bell housing - which typically indicates too long of a throw out bearing.

You do not want the throw out bearing pressed against the pressure plate diaphragm fingers - it'll burn up the bearing in a matter of time. The clutch fork/linkage must retract enough to keep the throw out bearing off and away from the pressure plate. You should be able to grab the clutch fork by hand and move it back and forth to "feel" when the throw out bearing hits the pressure plate. It does not have to come off much from the pressure plate, but it has to be off it. If the throw out bearing is adjusted too far from the pressure plate, when you go to push in the clutch, it will not release cleanly and you will clash gears during shifting. Manufacturers typically tell you to push in the clutch all the way to the floor and measure the air gap between the clutch disc and flywheel ( or pressure plate). Never did this. It either releases and I can pull a clean shift or it does not and needs an adjustment.

You can shorten the rod to suite where the clutch grabs off the floor. Some like it low, while others like it high. I don't like it engaging right off the floor, nor way up high. Prefer something about mid-way as long as the clutch releases smoothly and clean for a good shift. So you can play with that if you choose. As the clutch wears, the pedal will get closer to the floor and you may even find the the gears clash a little when changing them, then you go back underneath and adjust the rod again to bring the pedal back up.

Now if you cannot get this gap/clearance from the fork/throw out bearing, you may have the wrong length throw out bearing. They come in 3 lengths, short, medium, and long. Sometimes a kit will supply the wrong one and you will have to swap it out or the parts guy gives you what the parts book says and it is wrong.
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post #3 of 4 (permalink) Old 08-17-2018, 08:22 PM Thread Starter
 
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Thanks for the detailed response. I’ve never dealt with a manual transmission before so please bear with me. I’m working on a 65 and the only sping that I have is the return spring that goes around the fork and the other end of the spring is supposed to hook to the exhaust manifold flange. Since I switched to the Ram Air manifolds I had to rig something for the return spring that goes to the flange. Think I’ve got that figured out. When I pulled the engine and trans there was no boot on the opening of the bellhousing where the fork goes in. Since I saw them for sale I bought one and installed it. Seems like there is not much movement with it installed. Is it necessary to have that on there? I’m assuming its to keep debris out of there. So just to be clear, when turning the pointed end of the rod into the fork that is moving the bearing into the fingers and when turning it away from the fork it’s coming off the fingers?
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post #4 of 4 (permalink) Old 08-18-2018, 07:09 AM
 
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Originally Posted by Ohio66GTO View Post
Thanks for the detailed response. Iíve never dealt with a manual transmission before so please bear with me. Iím working on a 65 and the only sping that I have is the return spring that goes around the fork and the other end of the spring is supposed to hook to the exhaust manifold flange. Since I switched to the Ram Air manifolds I had to rig something for the return spring that goes to the flange. Think Iíve got that figured out. When I pulled the engine and trans there was no boot on the opening of the bellhousing where the fork goes in. Since I saw them for sale I bought one and installed it. Seems like there is not much movement with it installed. Is it necessary to have that on there? Iím assuming its to keep debris out of there. So just to be clear, when turning the pointed end of the rod into the fork that is moving the bearing into the fingers and when turning it away from the fork itís coming off the fingers?
The boot is to keep water/dirt etc. out. Most of the applications I have had did not have the boot or it was torn up due to age and I pulled it off. I personally don't think it too necessary to have. If you get some water in there, it will drain down to the bottom, but I think you would have to hit a really big/deep puddle to do that. Without it, I'll give you some more room.

The adjustment rod sounds about right. One way will extend it and push it into/up against the clutch fork and towards the back of the car which moves the throw out bearing closer to the pressure plate fingers. The other way will shorten the rod and pull the fork toward the front of the car and move the throw out bearing further away from the pressure plate fingers.

There should be a spring (yours may be missing) that goes from the clutch fork (you should see a small hole for its attachment) to the lower arm of the counter shaft. This holds pressure on the clutch fork against the adjustment rod so it won't slip out as it gets lengthened or shortened for your clutch/pedal adjustments.

The other spring you mentioned sounds like the pedal return spring which you have made work. On my '68, the spring goes from a hole in the frame (although the book shows a body bracket which most do not have) to a hole found in the upper arm of the counter shaft to pull it towards the firewall, thus keeping the pedal up against the stop block - or fully released.
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