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How much should the clutch fork move?

My1GLaser

Proven Member
1,565
31
Dec 4, 2006
Bartow, Florida
I did quite a bit of searching on this and couldn't find anyone who said how much their fork moves when the clutch pedal is pushed. Mine moves almost 1/2" and I don't think that is far enough, but I don't have anything to compare it to.

The problem is that the car won't go into gear while running and if I try to force it into 1st then the car starts to creep forward so I know the clutch isn't fully disengaging. I have temporarily fixed it by over-adjusting the rod under the dash, and I know the slave cyl won't self-adjust anymore. I can drive it right now, but I know its not correctly fixed. It isn't my DD but I wanted to drive her b/c its been down for 5 weeks since I smoked my street disc at the track. :(

I replaced my clutch disc with an SBC kevlar disc. FW is stepped to .608" ACT 2600 with only 400 miles on it. One shim under the pivot ball, which is only a couple thousand miles old. Taboo SS clutch fork is in the center of the "window." SS clutch line. Bled the clutch several times. The pedal assembly has been removed and all the bushings were replaced with bronze, and there is NO freeplay.

I am going to get another master & slave, but in the meantime this is driving me crazy and I'd like to see what is normal clutch fork movement. Plus, I have read enough threads where new MC & SC didn't fix the problem and people had to pull the tranny again for one reason or another. :barf:

Is there another slave that I can buy that gives more throw? I have read about the Isuzu slave cylinder, but I think it is only used by people with twin-disc... How can I change the ratio of pedal movement to fork movement? Yes I know the extended slave rod doesn't fix this.

Oh yeah, since OEM MC & SC are so FU(CKING expensive are there other replacements that people are having good luck with? Wagner, Beck/Arnley, Perfection Clutch...
 

pneumo

Proven Member
3,763
56
Oct 19, 2002
Bay Area, California
1/2" (12mm) is normal.
Have you checked all 4 trans to block mounting bolts to make sure none are loose?
 

My1GLaser

Proven Member
1,565
31
Dec 4, 2006
Bartow, Florida
Yeah, but I will check again. I just got done installing the tranny and torqued them all.

Mine is only moving 7/16" (11mm) when adjusted properly per Jacks transmissions tutorial video. I haven't measured to see how much it is moving now that it is over-adjusted though. The other thing that needs attention is that the firewall flexes slightly when the clutch pedal is fully depressed. I mean about 1/16" or so, but I losing a little bit of travel due to that.

I just remembered that Tim (twicks69) said in a thread I was reading that you should keep the tools in the car to re-adjust the the clutch once it is bedded in. http://www.dsmtuners.com/forums/dri...ct2900-vs-act2600-useing-sbc-kevlar-disk.html (post 23) The end of the thread the guy says that his clutch was engaging higher and higher off the floor, so there is hope. Maybe this is something specific to the SBC clutch that I wasn't prepared for, and I got my panties in a wad when I couldn't get into gear. Its a used dogboxracing stage 3 tranny and I want to make sure it really does shift awesome like the PO advertised.

Damnit I should have double-shimmed the ball, but the fork was in the middle so I left it alone.:banghead:

But what non-OEM master & slave cyl should I get?
 

twicks69

Supporting Vendor
3,931
1,111
Mar 12, 2004
Milwaukee, Wisconsin
Before this thread gets thrown into the clutch engagement issue master thread, lets see what we can do to resolve the situation.

First off, I would fully adjust the master cylinder rod in towards the firewall and bleed the clutch several times. Then, after it is bled in the fully-in position, I would then start threading the master rod away from the firewall (outward) until you reach the proper engagement for the clutch to have full disengagement, yet not over-engaging the clutch causing pressure plate and TOB damage.

Have you checked your master and slave cylinders for any leakage from the seals or at the bleeder screw or line connections?
 

My1GLaser

Proven Member
1,565
31
Dec 4, 2006
Bartow, Florida
I don't see any external signs of leakage.

I crammed myself up under the dash today to see just how far I screwed the adjusting rod into the master cyl and check out the pedal action. There is some black goo inside the boot covering the back of the master cyl. I know a while back I put some di-electric grease in there where the rod pushes the back of the piston. It appears that this black goo is somehow making its way into the clutch fluid which was a real dark color when I bled it. The fluid is only a couple thousand miles old and I wondered why it was so dark.

I do see what looks like small air bubbles coming out the back of the master cyl piston when I slowly push the clutch pedal. There isn't any fluid leaking that I can tell, just what looks like a couple small bubbles when I start to move the pedal. I had to really watch closely and I am glad I did, b/c I don't see any leaking fluid that would make me think its bad.

Slave cyl looks fine. I completely disassembled it yesterday and cleaned it. The piston had small scuff marks at the end where the paint was just worn off the piston but nothing major and no fluid leakage.

My theory is as follows:
The master cyl piston draws some air in when I push the pedal. It gets in front of the piston, so I don't get enough pedal pressure. When the pedal comes back and retracts the piston past the bleeder valve, the small amount of air goes up into the reservoir. I can't bleed this air out because it goes away as soon as I let off the pedal. The master cyl is worn and needs replaced!

Sound reasonable or do I not have a good grasp on how this thing works?

Do I have to buy an OEM master cyl? I was really thinking about getting a reman from NAPA b/c they have to bore it oversized and there should be more fluid transferring to the slave resulting in more slave cyl piston movement. Correct? Not a tremendous amount but maybe a mm or two which would make a difference.
 

pneumo

Proven Member
3,763
56
Oct 19, 2002
Bay Area, California
If your fluid is black already, it's a sign that the master or slave cylinder, or both, are worn. The black stuff is little bits of rubber piston seal that get rubbed off of the piston.

The right way to check the slave for leaks is to pull off the rubber accordion boot and see if any fluid drips out. If it does, replace it.
Master cylinder leakage will make a wet spot running down the firewall under the dash. Look for a slight stain coming down from the master cyl rod. Any wetness in that area is also a sign that the master cylinder is leaking.

I prefer OEM master/slave for clutches that are stiffer than stock since the quality and durability are better.
 

My1GLaser

Proven Member
1,565
31
Dec 4, 2006
Bartow, Florida
If your fluid is black already, it's a sign that the master or slave cylinder, or both, are worn. The black stuff is little bits of rubber piston seal that get rubbed off of the piston.

Oh, rubber from the master piston makes sense. :aha: I really wasn't sure what was inside since I've never had one apart. I didn't see any fluid coming from the back of the master cyl. I was under there 5-10 times adjusting the thing on Friday. Its a PITA to do by yourself...back and forth from under the dash to under the car checking to see if you adjusted it too far.

There was nothing dripping from the slave cyl boot when I took it off. Well until the piston popped out cause I didn't know there was a spring behind it.

OEM it is. All this from a smoked street disc turned into a built tranny, new FW, PP, MC & SC. God I'm broke now! :D
 

My1GLaser

Proven Member
1,565
31
Dec 4, 2006
Bartow, Florida
I put on the new OEM master cyl today and I rebuilt the slave cyl with a Beck/Arnley kit. Bled the hell out of it and I used a clear tube so I could see the air bubbles. Got them ALL out.

Its doing the same thing. So I over adjusted the rod about 1 turn and I can shift again but its still not correct. It is a little better because last time I over-adjusted the rod about 2-3 turns to get it where it is now.

While everything was apart I ground down the slave cyl ears about 1/8" so it sits closer to the fork. (One the slave not the tranny) I figured that was about the same thing as shimming the fork to sit closer to the slave cyl...

So is that making it better or worse or the same?

I still hope the SBC disc really changes its engagement point like some have experienced. I have 70 miles on it now and its still about the same.

Edit: I just found out when I rebuilt the slave cyl, that I have the wrong one. Apparently the 13/16" bore green piston is for a 2g or 1g NT. The red piston 3/4" bore is for a 1g AWD. I should get about 2mm more stroke on the slave cyl due to the smaller diameter still being moved by the same amount of clutch fluid from the master cylinder.

God I hope this works!!! :pray:
 
Last edited:

My1GLaser

Proven Member
1,565
31
Dec 4, 2006
Bartow, Florida
It seems to be getting a little better each day I drive it, and this is more for the archives than anything at this point. I get 15-16mm slave cyl rod movement with the correct 3/4" bore slave. :hellyeah: I knew the 11-12mm before just wasn't enough.

I have put 265 miles on the clutch and the tranny seems to be getting a little less notchy and the clutch seems to be disengaging better. Its still about 1" off the floor, but I did get another 1/4 to 1/2 turn on the adjustment rod today.

I also bled the clutch again today. I didn't get any air bleeding it the conventional way. So what I have been doing is pushing the slave cyl rod back into the body of the cyl and opening the bleed valve when I do that. I get some bubbles out like that, so either air is stuck near the piston, or the seal is slightly leaking. It really looks almost brand new. I am ordering a new OEM slave tomorrow, and I will be bleeding the clutch a for the next couple days again. :rolleyes: FWIW, using a clear bleed hose makes a tremendous difference. There are some bubbles so small that you would never know otherwise. Not to mention when there are really, really, really tiny bubbles grouped together that look more like beer foam that actual individual bubbles.

I also made another slave rod about .050" longer than OEM. Very small amount, but I figured it would help w/o the issues of a 1/4" longer rod. Honestly if the adjustment is correct under the dash, and the slave rod can fully retract and relieve pressure from the fork I don't see the problem with a longer rod...Plus the ends of the stock rod flatten out over time.
 

pneumo

Proven Member
3,763
56
Oct 19, 2002
Bay Area, California
A good way to bleed the clutch system by yourself is to remove the slave cylinder and hold it so the bleeder screw is at the highest point. Like you said, just pump the slave rod while opening and closing the bleeder screw. I also like to hold the slave cylinder as high up as possible to help bubbles rise up from the entire line, and tilt it at different angles to remove bubbles that might be trapped in the corner of the slave cylinder.
 
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