2g Yet Another Clutch Engagement

I went from stock disc, pp, and flywheel with a 100k miles on it, never been changed. The point I could change without any grinding (and not matching revs) was about halfway to the floor (3.5"). Any farther didn't make any difference. Stop was set to about 5.5" from the floor. Other than the clutch being badly worn (almost down to rivets), clutch dis/engaged fine for DD. Anytime boost hit, it would just slip slip slip.

In my build, I upgraded with the following: ss line (eliminated accumulator), southbend disc, act 2600 pp, and act flywheel. I didn't think of the engagement point at all when I made the changes because the worn stock components were gripping fine. However, fully assembled, back in the car, and adjusted as per Jack's how-to video - backed out the stop as far as it could (6.25" from floor) and then turned the actuator rod until the slave couldn't bleed back then backed it off half a turn. Free-play at this point was a very small twitch at the top of the peddle, the rest of the stroke all seemed to be moving fluid, same stiffness throughout the entire stroke...when it actually disengages, less than an inch off the floor, there is no apparent difference in the stiffness of the peddle.

When I replaced the main three, I did NOT replace the fork or pivot. Nor did I shim the pivot ball. Mainly my reasoning was "engagement point was well well off the floor, everything would seem to be in check".

Unfortunately, I ran out of time to rebleed the system, but the stiffness in the peddle doesn't really seem to indicate that there is air being compressed. The other unfortunate thing is I'm an hour away from my car (building it on my parents farm...nice garage) so it will be another week before I can personally visit it. I was able to get my dad to take a picture of the fork where it comes through the boot to see how far from center it is. (I'll post the picture once it comes in)

The other things to note is the rod was turned in farther than it was setup from stock. And when I was bleeding, I put on a one way valve and a length of tubing, loosened off the bleeder valve then slowly put the clutch up and down while making sure the reservoir was always full. That was my bleeding process...

Is there a possibility that I have air in my slave cylinder that I wouldn't be able to feel through the pedal? Pumping the clutch doesn't seem to change the engagement point.

To go from a non-full stroke distance of 3.5" from the floor to less than an inch, is something else going on here?

In short, I replaced:
clutch
flywheel
pp
line from master to slave
TOB

I didn't replace:
fork
pivot ball
master
slave

I have a 1G and was having a ton of clutch issues.

Replaced slave (had a cracked wall), replaced master (was leaking) and took out my entire clutch pedal assembly and welded it up (had lots of slop as many 1Gs do) and then we bled the crap out of it and only then did it disengage (and that's with the master rod almost fully extended). You'd be amazed at how much fluid and how long it took us to get all the air out!

If you're confident your master and slave are good to go, then bleed, bleed, bleed. Get a buddy (or your dad, a sibling, etc.) that can help you and/or at least watch the line. Also, every once in a while, close up the bleeder, pump the clutch until it's 'stiff' and then bleed again...this seemed to help us get a lot of the air pockets pushed out.

Not a lot of parts in the clutch system, but unfortunately they can all have a pretty dire effect if not in proper working order.

You have a good knowledge of the clutch system Andrew, and you performed all the correct measures to get maximum throw to disengage the pp from the disk without preloading the system.

I could write an essay on this, but don't feel like it right now Since you don't have easy access to the car, I'll just get straight to the point.

The Southbend disk is approx 20 thousands thicker than an ACT disk, PERIOD !

And if I may finish Reza's quote you need that much more "Trow" to disnegage the Clutch.
I'd say Bleed it the good old way then have a good look at the position of the Fork inside the Window.

If all fine; replace the Master and Slave and if that does not cure your problems then replace the Fork and Pivot Ball as well as shimming the Ball as required.

Ghislain

Here is the pictures my dad was able to take.

Fork seems to be a little too much in the center; I would defenately suggest that you revisit the Fork/Pivot Ball and shim the Ball.

Ghislain

Missed my edit window:

I'm also fairly certain it did bleed correctly the first go around because when I was adjusting the master rod and blocked off the bleeder valve, I could not depress the slave cylinder at all; if there was air in the line or slave, it would have compressed a lil then stopped... akin to how the peddle would have felt. At least, that is how I would imagine it...If you can push on the slave to move a column of brake fluid, you could compress a lil air.

Oh, guess I'll mention too the slave cylinder is not OEM, it was a Parts Source special because my stock one blew up in -30C...that was the most "fun" I ever had...changing a slave cylinder in the dead of winter lying on a patch of ice... It is about 1.5 years old with 6000miles on it.

Is this going to end up shimming it, or will simply replacing the fork and pivot ball be enough?

Also, is there any way to take on just the pivot ball while the transmission is mounted? can you sneak in a deep socket and a thin head ratchet behind the fork to operate on it? or a long wrench with patience?

In addition, because components are wearing and the entire fork and TOB is slowly backing away from the pp, would it be possible to find the perfect length of slave cylinder rod extension that I'm not preloading the system? I can get an extended rod then I have a lathe at the parent's farm that I can turn it down to the exact length I need without preloading/touching. The reason I'm getting to this is because I'm looking to get a Jack's tranny rebuild in the winter and this will only have to last me until then. If I find a winter beater, it will just be for few more months.

One more question, is the ratio between the slave cylinder and the master cylinder the same? ie, 1" of travel on the master = 1" of travel on the slave?

edit: Ghis, when replacing the fork and pivot with new oem, will you still need to shim?

Yes; you might still ned to shim.

Installing a longer Slave Cylinder Rod will only push the Piston deeper into the Salve Cylinder Housing. Ain't gonna help.

I would suggest that you replace the Fork and Pivot Ball and shim it; yep you will need to pull that Tranny out. I like to use a good old Washer that is about 0.100" (little thiner that 1/16") or about 1mm ish. You can confirm that the Tranny is properly shimmed by installing only 4 of the Tranny Bolts when you put the Tranny back in then inspect the Fork position inside the Window. Remove the Tranny and re-shim if need be.

I would alos suggest that you replace both the Master and Slave Cylinder with OEM. Aftermarket ones might work but your chance of a good results are better with OEM.

All in all it is no fun but take your time and do not cut any corners and you'll be gett'n that Tranny to shift like butter!!!

Ghislain

Sigh, just finally saw the light as to the problems that an extended rod will do - the clutch fork can only move so far before it will bottom out on the bellhousing through the rubber boot. More worn the pivot and fork, more likely it will bottom out with an extended rod.

Looks like I get to drop the tranny right after putting it back in with the engine Time to look up how to remove the axle without touching the ball joints...

i was able to remove my axels by simply disconnecting the strut, tie rod end, and stabilizer bar. Not sure if DSM's are that easy.

aftermarket slave and master cylinders will almost never stand up or properly release an aftermarket clutch like that

Shimming the pivot ball helps only if they are worn out badly. Other than that it just pushes the slave piston up its bore even further and makes the throwout bearing ride the pp fingers with more pressure at all times. It doesn't matter how much shim you add after a certain point, it won't change the amount of throw you have at the slave one bit. It won't even give you the extra throw you need for a thicker disk either.

A little shim, i.e. 1mm is good on a new ball and fork for future wear and tear. I tend to do the same as Giz mention above.

On the other hand, I did mention the disk is 20 thou thicker than an ACT disk, uncompressed. ACT PP are designed to be used with ACT disks, which have a flattened out marcel. Uncompressed thickness is what affects the engagement point.

I've already been through this BS with the southbend disk. The disk is soo thick it throws off the pivot angle on the ACT pp fingers. This is why it feels like it will work. With the car off the pressure feels good in the pedal, but still only disengages at the end of its throw !

I actually took my ACT flywheel, ACT 2900pp and southbend disk, bolted them all up and put them in my press to simulate a clutch system. I took the measurements and came up with my conclusions.

You may have noticed that the pp fingers were almost flat with the disk bolted up. I almost tossed the damn thing like a frisby. If you like your clutch engaging off the floor and killing syncros up top, keep using it with the ACT pp as is!

Changing the master/slave and pivot ball/fork may help a little, but its not gonna bring your clutch pedal engagement height back to like 3/4 of the way up. Try them out, if no difference, post back and I'll tell you what the solution is

I'm glad I actually do my own fine analysis of aftermarket parts that I install on my car instead of just blindly following the hype!

Good luck with getting it to work, some guys love it some don't

Andrew, I'm not sure what your symptoms are but if you're having clutch disengagement issues then Reza is right... it's the South Bend disc / ACT 2600 pressure plate combo that is the problem.

I went through all this myself a month ago. I installed a new ACT Streetlight flywheel, South Bend TZ-Series Kevlar clutch disk, and ACT 2600 pressure plate.

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Once I got everything all back together the clutch would not disengage. I tried flushing the clutch fluid, bleed it extensively, and set the master cylinder adjustment rod, all as per TRE / Jacks Transmission instructions. No dice. With the engine running the transmission would not go into gear.

Upon doing some research, I discovered that this is particular issue is somewhat common when trying to pair a South Bend disk with a ACT pressure plate. It's partially due to the thickness of South Bend disks and partially to ACT design changes. Basically it's hit or miss whether they'll work together.

So I ended up pulling the transmission again, measured the South Bend disk at 8.65mm (0.340") thick and my ACT disk at 8.10mm (0.319")... about a 1/2 mm difference. I also measured the flywheel step and it was within spec at 0.611". Then I put an ACT disk on (in place of the South Bend) and put everything back together.

Disengagement issue solved! No problems thereafter.

I never did say which exact disc I was using, but I'm going to assume that either way, the southbend kevlar disc I have is indeed thicker than an ACT disc.

So the springs in a pp are the real factor here then when trying to run a thicker disc.

I hope I understand when I say that the using a thicker disc in the ACT pp results in not operating where it was supposed to and is in a sense preloading the fingers. The fingers being logarithmic in nature and as throw is increasing, the proportional amount of finger movement on the pp face is getting less - it isn't linear.

If this is all the case, there seems to be immediately three viable options:

1. scrap the southbend disc and get an act sprung 6 puck
2. scrap the act pp and get a southbend pp
3. slip the living hell out of the disc to wear away until the fingers will disengage earlier and readjust everything

The one other option I see, is changing the whole leverage system of the fork, pivot, and slave to allow more travel of the TOB towards the pp with the same slave travel...the trade off being more pedal effort. This would either: increase the length between the TOB and pivot or decrease the length between the pivot and slave cylinder impact. The end result would change the ratio between the movement of the slave vs movement of the TOB. For example, going from travel ratios of 1":1" slave:TOB to 1":2" slave:TOB. All while hoping I don't ever bottom out the fork on the bell housing and that over extending the pp fingers out of their "typical" range doesn't break them off. As you said, there is a logical limit to the amount of shimming you can do before you either preload the pp or mess up the slave's throw.

I did come across your thread where your old disc and pp broke apart and you ordered the southbend disc. I wasn't able to find the end result of all that though.

It is really strange that the ACT 2600pp and southbend kevlar disc has found its home into so many DSMs and I can't find anything about it being either preloaded for a proper engagement point or the engagement point is at the floor.

I would love to hear your advise before I order a whole bunch of parts that won't necessarily fix the real problem, which I think we have established is the inability of the pp to proper disengage a thicker disc because of the physics of the pp fingers and springs within a limited space system.

If you have some links, I would love to take them for a read. Particularly over the ACT design changes. I tried digging up info direct to this combination and all I find is "+1 act 2600/southbend combo" posts with no substance about engagement point, preloading, etc...

Is it the newer PPs that are a problem or older PPs?

I think I now know the real reason the person was selling it...

It seems like switching from a southbend to the act would be the least paint in the ass

Could a larger flywheel step help?

Yup 3 options:
(1) Remove the SBC disk and use an ACT disk.
(2) Use a lighter SBC PP with the same SBC disk. The heavier SBC pp's suffer from the same issue.
(3) Run a larger step height of at least 0.618" ^^^ Rob said it!

I actually tried the larger step height of 0.618, 2nd time I pulled the tranny. 8 thousands off the flywheel and it brought up the pedal height about another 1/2 inch ONLY.

I don't like clutch's engaging near or at the ground, but I got mines to shift well. From the research I did messaging a few other guys who got this working, they reported the same with it engaging off the ground, but still shifting very smooth up top.
I attribute that to the kevlar material which is softer.
Some guys actually like their clutch engaging off the ground, and claim its good for racing but to each his own If I had known the sbc disks would engage near the floor, I would not have bought one. If I knew the thickness before I bought it, I would have steered away too.

Anyhow 1" off the ground was still not what I prefered, so I pulled it out again and am using an ACT 6 puck sprung like I had previously with the step height of 0.618" on the flywheel.

What a great setup I have now, I would never run a 0.610 step height again on a DSM. I might even go upto 0.620" with an ACT disk next time. A bigger step height leaves you more room at the master to get full throw, at the expense of clamping pressure. ACT pp's have enough crank killing clamping pressure anyways

My clutch right now engages 3/4 up the top of the throw, not at the bottom, and my high rpm shifts are smooth and effortless.

If you really want to keep all your current clutch components and make this work at 3/4 of the way up the clutch pedal throw, I would suggest a step height of 0.625. Otherwise live with it and somewhere half way through the clutch disks life, it will fall into spec and shift the way it was intended.

I have a built tranny in my car with new syncros, so I didn't really want to wait till the disk wore down and fell into spec.

Main difference in thickness I attribute to the two disks, is the marcel in between the materials. ACT disk has a flattened marcel, SBC has a springy marcel.

IF sbc actually just flattened the marcel out in the disk like an ACT disk, it falls right into spec, and I'd be all over the sbc disk again.

Tim Zimmer did tell me that they will be making thinner disks for the next batch. If they are actually around 0.313" for the next batch, I'd try it over an ACT disk.

As Rob suggested, changing the flywheel step could potentially help. Or switching to Isuzu slave cylinder (longer throw).

Switching to a South Bend pressure plate should work in most cases, but not all. Some people still have had issues. If you want to stick with the South Bend products, then Tim Zimmer @ tmzperformance.com would be the best person to talk with. He has intimate knowledge of all the potential issues and solutions regarding these clutches in DSMs and has been working closely with South Bend.

I got most my info from the ECMLink forums. Not sure if you have access, but here's a link: http://www.dsmlink.com/forums/showthread.php?t=60281

I chose to go with a ACT disk since I already had possession of a brand new one.

I think what I'll end up doing is:
new fork
new ball
1mm shim
new oem slave
act sprung 6 puck

save the southbend disc for when I need to resurface my flywheel down the road. Any tips for storing a kevlar disc? What is the maximum step height you can go before you need to replace the ACT streetlite flywheel?

Thanks to everybody so far for the great input into this. Really wish this more out in the open or else I wouldn't have dicked around with mixing and matching pp to disc and stayed purely with one company or another. But as Reza said, I got caught up in the hype and didn't hear anybody say anything about any negative consequences running this combination.

edit: Like you Reza, I love my clutch to disengage near the top of the peddle. I don't need to brace against the floor while waiting for a light change - I've come to accept my legs are the strongest muscles I have...especially after so many years of track and field and volleyball.

Isuzu slave has a shorter throw, not longer. They are to be used with twin disks which require shorter throws.

If they were longer, 1g guys would be using them already as we like to get the most engagement as possible from a full stroke at the master.

I have yet to find a smaller bore slave which would result in a longer throw. I have put some thought into this already. If someone actually bored out the clutch master cylinder to accept a bigger piston, you could use a rebuild kit from a car with a more heavy oem clutch. This would result in more throw and most likely a stronger master clylinder that could last years longer than an oem dsm one. In my years of DSM'ing I haven't had an OEM clutch master cylinder last more than 2.5 years till it started leaking.

Then again, there is only so much throw you can get before the pressure plate fingers hit the clutch disk springs, and if you can't get a disk to disengage by then, there are issues. Its better to just have a properly working clutch system instead of trying to change parts to achieve more throw.

In all honesty I realized this issue months ago, but didn't want to be the first person to go on about the southbend disk. Everyone else had superb reviews on it so I just kept my mouth shut, till a few threads about the same issue showed up. I realized that some reviews on products are not always the real story.

Anyhow, new fork, ball, 1mm shim, slave and ACT disk is what I'd do too.

My ACT streetlite flywheel is at 0.618", It can go deeper if needed.

Also FYI the ACT 6 puck sprung is a few thousands thinner than an ACT street disk. Its a little harsher but not as bad as an unsprung 6 puck. If quick release, good pedal height is what you are looking for, thinner disks are the way to go.

Like said, the best option is to stick with one manufacturer, that way you know the products should work as advertised. Believe the SBC disks use to work with ACT PP's, no problem but ACT made some changes & its no longer the case.

I'm running the SBC SS PP with the TZ/FE disk. So far so good but haven't really abused it yet. It does engauge about 3/4's of the way up as well.

Believe SBC is also working on a revised SS-X PP (think its out by now) as there were some issues with certain disks, believe the FE.

I ran a act flywheel that was stepped too shallow with my last clutch setup (measured around .605-.606 with my PA dial indicator). Figured oh well, the disk will wear & it'll be fine. This is probably not the case, that setup dragged after about 5500rpms when testing. I just ran it as it seemed to shift alright but I'm starting to think I hurt the syncros in my built tranny

Yep, lucky right now don't have a built tranny (still stocker...getting a lil notchy though)...yet, which is why I was wondering how far I could weasel with it before I get a new transmission. But since the problem is with the tolerances on the block side, I might as well do it now instead of later.

After this...it is boost leak test time...YAY!!

Wow; lots of interesting info in this tread.

Let us know how things goes for you.

Ghislain

Well frack...

When I had the transmission first off I noticed that the one axle seal looked a bit roughed up. Since I was dropping the transmission again, I thought I might as well replace it.

This is what I found upon taking the seal out and taking a much better look:


Don't know how the previous owner did it, but this casing is done for. Trying to use as is the new seal doesn't seal against the raised face. Trying to remove the chunk of metal, I'll have no sealing surface. And if I try to trim it down, I have a high chance of metal pieces inside the transmission and will have a crack along the sealing surface. Could jb weld it and very carefully take it down, but I don't feel like half-assing after all I have done so far.

So looks like I'll be getting that new transmission sooner than later.

Did have a chance to measure the thickness of the ACT 6 puck sprung vs the Southbend and sure enough, Reza was correct - 20 thou thicker was the Southbend over the ACT.

I'll update again when I get the new transmission all bolted in.

Another question. The ACT disc I got came with a small blister package of 'clutch lube' with the note: "read the installation instructions" I went to their website and there was nothing about the lube nor on the back of the clutch packaging. What is this stuff? Lightly spread on both sides of the clutch pads? Is it for the splines? The only searches I could dig something up on was a snowmobile forum which talks about a dry lubricant to increase clutch life. Just an oddity to me really having to apply something to the clutch surfaces before installing one.

That pakage of Clutch Lube is defenately NOT for the Clutch Disc or Pressure Plate.

Use a bit on the Splines, between the Sfift Fork & Pivot Ball and on the Shaft where the TOB goes on.

Ghislain

I have heard of these issues with the southbend discs with the act pp and I looked into(reading other threads and such), its seemed like people were saying that act made some changes to the pp which resulted in issues with the pairing of the two. I wasn't to worried because my 2900pp was purchased back when they first became available. However since the machine shop recommended I purchase a new pressure plate - that's what I did(another act). Now my southbend disc was however purchased used but was described as approx. 10 or so 1/4mile passes and little to no street use.

I meant to measure this disk a long time ago(when talking with Reza in person about the subject - like early spring) but couldn't find any of my measuring tools for awhile - the following measurements were taken with a digital caliper - I took several measurements and all were with in 0.309" to 0.316" range. The disc imo looks to have lots of life left in it. The disc did have a 10sec. pass on it, but doesn't appear to have very much wear at all.

The measurements are below what a new act disc would have so I'm going to go ahead and use the southbend disc with new act pp.
Does anyone think that this disc worn that much with such little use? Should I find another means of measureing? I'm thinking that at some point maybe southbend started making them thicker. Any thoughts on any of this?

I'll have an answer in a week

I knew I measured, but I can't remember for sure what each disk measured.

I'll measure the southbend when I get back out there with my new tranny.

Got the new Jack's transmission, slightly shimmed, with the act sprung 6-puck instead of the southbend and all is right with the world again. lil bit of free play at the top, nice engagement all the way through, and back to just slightly touching the clutch in and shifting on matched rpms.

Now...just need to relearn taking off from first, slightly different from a burnt out stock disc to a 6 puck

Glad you got it running well with an ACT disk now.

Charles, you should be fine with that thickness on the sb disk.
From my understanding SB did start making the disks thicker at some point.

Also, as far as I can remember ACT didn't "JUST" come out with a new design for their pressure plate recently. Their new design PP's have been out for many years now. I think a company like SBC should put a little more research & design into their clutch disks, then to say "the problem lies with ACT changing their pressure plate design".

From my own research it seems like SBC changed their disk thickness, because the thickness and engagement point of new ACT disks has always been the same for me for the past 10 years.

I have never noticed an engagement point difference or disk thickness in the previous and newer ACT clutch's. I have ran both and have easily been through six to eight ACT street and 6 puck sprung disks over 10 years.

If I was designing clutch disks for DSM's I would have known that 0.34" thick 2g oem clutch disks never worked with even the "older" design ACT pressure plates. This has been common knowledge in DSMs for that last decade. Making a disc that is 0.34" thick then saying that ACT changed their design, is plain BS

I hate misinformation on the internet.