How to fix your clutch that won't release.

[bastarddsm]

Over the years I've done a lot of testing with these cars. I've probably spent more money on testing clutches than an average build costs. - Not bragging, just saying I've tried a lot of stuff. One thing that sticks out, is virtually all performance clutches require more throw out bearing travel than stock to fully release the clutch. If you have a heavy pressure plate that touts a light pedal, than it's going to be bad.

Where we end up is something like the classic ACT2600 is right on the borderline of working with the stock clutch release system. That's why if anything at all gets worn it won't release, and sometimes even the smallest improvement can fix the issue. The solution is somewhat simple, move the TOB further. That's not hard to do, put a smaller slave cylinder. One from a n/a 3000GT works will improve release, but it's gonna give you a heavy pedal. If you want to fix it for real you need to work through the whole system. I end up reworking the pedals to have a longer pedal throw, and then use a wilwood master cylinder with an adapter kit to utilize that increased pedal throw. This gives you more release movement, but not an increase in pedal pressure.

I've said it many times, my favorite clutch in my car has been a 2900 with a solid hub street disc and my pedal mods. It's just awesome. Shifts killer, drives nice, doesn't tear up parts, disc doesn't chunk out, pedal pressure is low and it's cheap. Anyway I thought I'd share a couple pictures of my pedal mods and the master cylinder setup. You can see in the pictures of the pedals I mod the upper stop so the pedal can come up further and then clearance the other end some. The pedals remain useable with an oe master cylinder as well.

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[1cleangsx]

So assuming you have a healthy rebuilt pedal assembly, one option for better release is the smaller slave for a NA 3000gt? I might look into that. Even after I rebuilt my assembly last winter, which gave me immediate movement of the master cylinder, my southbend ssx “2700lb” plate was still picky and seemed to have a narrow adjustment window. It did shift like butter at 8500rpm’s from 2nd to 3rd, but adjustment was still more difficult than I expected after fixing the pedal slop

Adjustment aside, I love the streetability of a strong single disk, I’ve seen many posts of twin disk users saying they’d go back to single if they could get them to shift at high rpm. I believe you and @donniekak have both posted about modified set ups that got the heavy singles to work, thank you for sharing

 

[Drewpy Dawg]

This is very interesting. Do you have a measurement of how much more pedal travel you get from this?

 

[pauleyman]

Over the years I've done a lot of testing with these cars. I've probably spent more money on testing clutches than an average build costs. - Not bragging, just saying I've tried a lot of stuff. One thing that sticks out, is virtually all performance clutches require more throw out bearing travel than stock to fully release the clutch. If you have a heavy pressure plate that touts a light pedal, than it's going to be bad.

Where we end up is something like the classic ACT2600 is right on the borderline of working with the stock clutch release system. That's why if anything at all gets worn it won't release, and sometimes even the smallest improvement can fix the issue. The solution is somewhat simple, move the TOB further. That's not hard to do, put a smaller slave cylinder. One from a n/a 3000GT works will improve release, but it's gonna give you a heavy pedal.

is the piston even smaller than 3/4"?
I've posted about 13/16 and 3/4 slave bores but I had not gotten into 3000gt stuff. I’m legitimately curious.

If you want to fix it for real you need to work through the whole system. I end up reworking the pedals to have a longer pedal throw, and then use a wilwood master cylinder with an adapter kit to utilize that increased pedal throw. This gives you more release movement, but not an increase in pedal pressure.

I've said it many times, my favorite clutch in my car has been a 2900 with a solid hub street disc and my pedal mods. It's just awesome. Shifts killer, drives nice, doesn't tear up parts, disc doesn't chunk out, pedal pressure is low and it's cheap. Anyway I thought I'd share a couple pictures of my pedal mods and the master cylinder setup. You can see in the pictures of the pedals I mod the upper stop so the pedal can come up further and then clearance the other end some. The pedals remain useable with an oe master cylinder as well.

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[bastarddsm]

Yeah, the 3kgt is like 0.700" or 0.625" I actually have one on my all motor car right now as a "quick fix" It's got an OE mitsu PP and an ACT disc, and it wasn't happy shifting at 10K. The 3k slave works ok with the light pressure plate, but isn't ideal.

When you start cranking up the pedal pressure you get more deflection. The pedal shaft twists, lines expand, seals swell, ect. It's possible you could get into a heavier pedal but no additional TOB travel depending on the setup.

By doing what I do we keep the pedal pressure down, and the losses to a minimum. I even went as far as doing needle roller bearings in my pedal assembly to see what all could help. In the end best would be a new stiffer pedal assembly, but noone will want to pay for it.

Here is a video I made on the subject. https://fb.watch/q7Bb0WmBmm/

 

[pauleyman]

Interesting info. I'm really shocked I haven't heard more about this. Honestly I figured long ago somebody would've built a jig to measure slave/fork travel. Once you max that out that's it. Only other variable are fork angle and flywheel step height. I would also say there is probably a maximum TOB travel for a given fork angle/travel arc. That would for sure support the idea is somebody should shim anything. Would rule out a lot of guesswork.

 

[Anfurnyy]

I've read in posts of yours in multiple places mentioning "larger diameter" slave cylinders, could you give us some part of model numbers of slaves that you're talking about?

 

[rdeis]

Sorry to revive the thread-- where'd you get the wilwood adapter? I have a 3/4" bore wilwood master on the way from STMTuned as we speak...

 

[steve]

Sorry to revive the thread-- where'd you get the wilwood adapter? I have a 3/4" bore wilwood master on the way from STMTuned as we speak...

My guess is he made it.

 

[chrisman287]

Sorry to revive the thread-- where'd you get the wilwood adapter? I have a 3/4" bore wilwood master on the way from STMTuned as we speak...

1G DSM Wilwood/Girling Clutch Master Cylinder Conversion Kit – White Shed Speed