KenRudd

This window was on the '86 Mossgreen. Puzzled me when I first saw it, as this was my first 928 Manual. Clutch is still perfect.

mark kibort

you got this wrong as well. your experience, doesnt match my experience on 4 different clutch set ups. you are wrong due to the fact that there COULD be wear in your system and we have seen the problem that these devices are KNOWN to solve, by doing as you suggest. thats not religous, this is common sense.
Glen, as the Hs wear (the friction) they migrate back to the rear of the car. in other words, they get wider. this causes the intermediate plate to be retracted all the way to the pressure plate...... then it drags.... causes the KNOWN problem. by the adjustment, you solve this problem...... if what you say was true (for all cases, not your own worn out set up) THEN, why even adjust it???? why even have friction "H"s???? i mean, you are hysterical, if you call me religious and yet you see one occurrence and think its the way it is, without thinking about what the parts, like the "H"s, are designed to do!!!!!!
com'mon Glen, you are better than this!!!!

lets rephrase your comment........ My facts do support the design and dont match Glen's experience. Glens facts only support a one off occurrence. that makes a lot more sense, dont you think?

LT Texan

Adjust it until it does this:

mark kibort

actually, i dont understand how they can be self adjusting and (as far as my belief and research has proved) if there is too little of a gap, the int plate provides enough friction to spin the drive line via the flywheel AND if the gap is maxed out, it contacts the surface of the pressure plate (same exact effect). So, when in adjustment all is free when you push the clutch pedal down.

Ive nailed the H adjusters at 1mm.....that gap is the adjustment .. they are riveted and have been riveted in the same position for many years now , racing full seasons every year! why does this work and what is the draw back?
well, it works because if the discs wear too much, the gap will widen and eventually hit the other side of the H adjusters. at that point, the fixed point of the H adjusters against the pressure plate is ok and working, but now the INT plate will not allow the discs to put pressure on the flywheel.... so , they willl start to move toward the flywheel. this is not a problem, because the rear part of the adjusters is moving toward the engine, and there is still a gap for the discs to retreat, but it cant move rearward enough "still" to hit the pressure plate. this is the situation, where if the discs were worn, the H could be pressed all the way back without issue. Glens discs are worn or there is something out of spec on his system. this is because , if you have a propery set up clutch pack, all the way rear ward adjustment will allow the int plate to go rear ward to hit the pressure plate, and no gap will not release the int plate and discs from the flywheel.

SO, the only drawback with "pinning" the H adjusters, is that if you excessively wear the clutch discs, eventually, the H adjusters will not allow the pressure plate to push the INT plate to the flywheel to get friction. there will be a larger gap, but the rear position of the H would not have moved, the discs being thinner will position the INT plate in the compressed position closer to the flywheel. a normally friction positioned H adjuster would be easily moved inward as the discs wear to this extent.

read this 3 to 4 times Glen and you might finally get why you have seen what you have seen. there is a design purpose of the H adjusters. its to provide a window of position rear ward, to release the clutch, but not too far as to drag on the pressure plate. the front tabs are a limit for moving the int position under max disc wear.

Now, a little story...... both scot and I were at the track racing our 928s and both of us had weak adjusters. the only way we could get the car into gear and stop the driveliine from spinning was to make the gap 1mm. PERIOD. this was expected and adjusted like this for years..... then, i finally got he idea to pin them in position....... we never had a problem since. AND, the reason there was a problem, was because the gap was too large.... advising someone to make the gap large and install is stupid and will just cause a BIG problem and a requirement to drop the lower bell housing and adjust. (unless you are glen and have a one off system)

mark kibort

1mm vs 1.5mm might look like this..... so i think you nead to measure that movment near the H's. if this is 1.5mm, it will hit the pressure plate and keep the driveline spinning, making it impossible to put in any gear

Ad0911

Well, I subscribed to this thread just in case, because I will definely encounter this poblem whatever it is once I put he clutch inthe car. I still don't grasp the prolem (rear clutch disc dragging?) and don't understand the adjutment. Last time I took the cluth assembly o a Porsche dealer during a club tech meeting, they broke off a piece of the fiction material. So far for demonstrationwork on my car!

GlenL

Gosh, Mark, thanks for the condescension. tl;dr, although I skimmed.

What would be exceptional would be to find out how the engineers thought the clutch would work. Why are there adjusters at all? Do the adjusters move to accommodate wearing clutches? Is the friction in the adjusters carefully balanced with the spring force of the intermediate plate?

Something that's clear is that there's problems if the adjusters get loose. That's why pinning works: you find the right spot and hold it there. The discs wear slowly so that works for some people.

What I think is that the adjusters are for manufacturing variances. The purpose of the adjuster is to hold the spring-loaded intermediate plate from pushing the second disc back onto the pressure plate. When the clutch is applied, the PP is pulled back and the IP springs back. This releases pressure on both discs as long as the IP doesn't spring back too much. And like disc brakes, it doesn't need to be a gap but just an elimination, or nearly so, of force. That allows the synchros and gear oil to apply enough resistance to make the discs stop spinning.

When the manual says "make gaps even" it's just expressing Teutonic precision. The gap widths don't matter as long as the force on all four disc sides is released.

The Pressure Plate applies a huge force compared to the adjuster friction, btw. The adjusters will do nothing to limits it's action and will move forward if it can.

So why have I had success with "crank 'em back?" Because the parts are actually working right and the adjusters are being forced into a good spot. With them to the rear, the pressure plate will force them forwards when it move the intermediate plate.

You keep casting erroneous statements about "maybe Glen's clutches are this or that." That's all pointless. The first time I did this it was after installing a new clutch kit, with old IP and the second time was new IP and PP and re-lined discs. Flywheel ground in both cases. The adjusters felt stiff and that's critical.

So, in bold:

The adjuster (unless pinned or at the end of it's travel) will never stop the pressure plate from forcing the intermediate plate forwards.

The adjuster's purpose is to stop the intermediate plate from springing back and trapping the rear disc to the pressure plate.


We could discuss this more but, as history would support, you'd repeat you points and how you're "right" and everyone else is "wrong" until you've got the last post and consider yourself the "winner." Please accept my invitation to do that.

mark kibort

I figured you would skim.. but about the condescension? you know me, I don't throw the first punch. you basically called my logic as being a religious zelot. so, you get the appropriate and measured response... However, in reading my response to you , it seem pretty warranted, based on your single experience of pushing the adjusters back and having it "work".

Again, the reason I respond with such conviction, is that I know someone like you should know better. I say this with the utmost respect by the way.

I think I can answer your questions , if you haven't picked up on how the entire system works with the INT plate.

1. the adjusters allow for the INT plate to retreat from the flywheel but not too far as to then have the spring pressure push onto the pressure plate surface. you need them because of stacking tolerances of the parts in the clutch pack AND ACTUATION SYSTEM . 1mm is all you need the system to retreat .

2. yes, the adjusters can easily move inward due to wearing of the clutch discs. there is 400lbs of pressure on that plate, and the adjusters' can move via this pretty easily.

3. the H adjusters have NOTHING to do with the spring force of the INT plate. those springs are only there to retract the INT plate and hold it in floating position when the clutch pressed in. the H adjuster friction has to be able to hold position when INT plate is floating, or they will move back, and then create the problem that most see if they are adjusted too far back

so glen, I like everything you say on your response below, EXCEPT why you think you can push the adjusters all the way back and have the pressure plate plush the adjusters in proper position upon assembly. you have forgotten one major factor. there is about a 1mm gap to the rear of the H adjuster before it touches the pressure plate and causes the problems you describe.. AND there is about 1mm on the front of the adjusters as well. (so if the discs wear , the pressure plate will push the H's forward to make contact with the flywheel, as pressure plate pressure is no match for H adjuster friction.)

So, with a stock set up of new or intolerance discs, using the push back method, the pressure plate will make contact with the INT and flyheel and only have to move it .5mm or so, leaving 1.5mm of a gap. this allows the INT plate to retract TOO far rear ward and make contact with the pressure plate friction surface.!!!!!!!! do you see??????? Now, if the discs were more worn, say near .5mm worn , then you might be close enough to make it all work by using your technique.

In other words..... Porsche designed the adjustment of the system to work as I say it does.... by doing what you say, you are basically saying the Porsche design and instructions are wrong or not needed and that the engineers missed your simple observation that works, ONLY for you Glen! really! like I said, if your method did work, I wouldn't have had to pin the H adjusters , OR Scots, or MINE so many times after they Migrated back.

the 3 should be even too as far as adjustment, due to the vibration they could cause when the clutch is in at 6000rpm...... that force might be able to move the H adjusters , so solve that by making them near even. (about 1mm per H adjuster)


EDIT: Glen... another way of looking at the adjusters on a "normal car, not yours", is that when the adjuster is adjusted correctly (about 1mm gap) there is 1mm gap on the inside as well. (this is to accommodate wear of the discs beyond 1mm where the H's can be moved by the pressure plate automatically).
this 1mm gap on the inside, and 1mm gap adjusted to the rear, means if there was no gap on the front side (your advice to have the pressure plate do the movement or adjusting) means that there will be a 2mm gap on the rear.....> THIS MEANS BAD THINGS WILL HAPPEN>>>>> you will get the contact this design is trying to avoid...... YOU NEED 1mm or less to have the system work....IF you were able to push the H adjusters all the way back (as DEVEK once said to do too) you have worn or thin parts ..... I have made this adjustment 30+ times when the H's had moved all the way back. it allows for pressure plate INT via the disc contact that keeps the driveline spinning. its not a matter of right or wrong here Glen, its the way it is. unless you have info other than anecdotal that shows otherwise.

mark kibort

a couple of more things here... I dont know why you had luck with pushing the adjusters all the way back, but you did say that you had the flywheel ground down, and that could absolutely be the reason... as you said, it was for both cases. (new and used parts)

about the H gap.... no, its not like the disc brakes, because the disc brakes are fixed. the clutch discs are not fixed and have an uneven surface as well, not to mention there is no way of making the "retraction" perfectly even with the H adjusters, so even if there is a little "fur" on the disc surface, if it is close to the pressure plate, there is a tiny amount of friction.. that's enough to spin up the driveline and make that inertia impossible for the syncrhos to stop... THIS is why you need .75mm gap. like i said, on flywheels that were NEW or not ground, the gap needs to be .75mm or at the most 1mm, or the retraction of the rear disc will contact the pressure plate and spin up the driveline. (bad).

(BRAKE residual friction ANALOGY NOTE): ever spin a rotor with the wheel up in the air??? the disc friction is actually significant. if the brake calipers could spin, it would take the rotors on a spinning ride, right???? exactly the point here. there cannot be any touching of the discs to the flywheel or the pressure plate when the clutch is pushed in... if so, the driveline spins up

you make a contradiction in your response above as well.. you talk about the mechanism of how you don't need any gap at all, just a release of friction pressure, but if that was the case, the H adjusters would be moved all the way forward. (a situation that is impossible if you start with them all the way back). This, making the gap too small, has HUGE problem. again, its because it doesnt take much to spin up the driveline.. in this case, a too small of a gap will certainly allow all the pressure plate pressure to be removed (like your brake disc analogy) BUT, because they are still touching, even slightly, the driveline is spun up, making it impossible to shift. (by the way, once in gear, shifting is fine , because this mis-adjusted H adjuster causes only a little friction)

as far as the pressure plate making the adjusters move , yes, i agree. they will make them move because the H adjuster pressure is about 100 to 200lbs max. (you can make them move by pushing on them with both hands on the INT plate on the bench). the INT plate spring pressure is only a few lbs, who's only job is to retract the INT plate rearward as you say.

So, in summary:

1. the H adjusters on a healthy system needs to be set at .75 to 1mm.
2. do not push them all the way back or the rear disc will contact the pressure plate surface and spin up the driveline. EVEN even when installed the pressure plate pushes the H adjusters to allow for driveline clutch and flywheel max friction. Because if you push the pedal in, the gap will be maximum at the H adjusters, meaning the rear disc will be pulled back too far and pushed into the pressure plate and make contact and spin up the driveline.
3. If Glen saw this "push all the way back " technique work, then it was because his flyweel was machined as he had said, or had thinner parts stacking up the distance. we have alll seen the problem.. but not Glen. Hacker, me , Scot, Greg brown, etc etc.

Vilhuer

Not gonna spend whole night reading what Kibort says.

This is how twin disk clutch works.

1. When pedal is pressed pressure plate will release the pressure and move back.
2. When ever possible intermediate plate springs push intermediate plate as far back as it goes. Self adjusting H thingies at intermediate plate limit its movement. This should leave room for disk II to rotate freely. Pressure plate movement should be about 2x intermediate plate movement meaning there is about equal free space for both disk I and II and clutch is disengaged.

Where adjustment comes into play is when disks wear out. Pressure plate force is stronger than H thingies can take staying still. Meaning when disk I gets thinner pressure plate pressure pushes three H's forward and intermediate plate can move forward to take up the slack and disk I is doing its job. Thats also why pushing H's all the back when setting up clutch should work. Pressure plate must be strong enough to push H's forward as needed.

When ever H thingies move forward position where intermediate plate can move back when pressure plate is pushed back also moves forward. Free area on H's is intermadiate plate movement range. This means intermediate plate position where its springs push it changes forward at the rate H's migrate forward. This means free space for both disk I and II should remain equal as long as both disks wear at about same rate.

There are two common failure modes for this setup which are specific to it. If clutch shaft bores wear either disk I or II can't move back to position it needs to be when pressure plate goes back as pedal is pressed.

Another possibility is if H thingies are not tight enough to hold against intermediate plate spirings its possible H's can move when pressure is released by pressure plate. This means intermediate plate pushes disk II against pressure plate and clutch is not completely released. H's must be tight enough to be able to hold intermediate plate in any position along its movement range where ever its set when parts are on the table. At same time H's must allow movement of themselves in case pressure plate can push disk I, intermediate plate and disk II forward.

By pinning H thingies into one single position Kibort or anyone else is creating situation where intermediate disk movement is permanently limited to range what ever free space there is in H's. This means there is no possiblity for H's work like they should when parts wear. In the long run this means free space for disk I and II is not evenly split when pressure is released. In practice same situation can happen even when H's can move if all parts are not correctly worn together.

Its actually very simple setup and works fine when parts work like new. Cost of the parts is such that few 30 year old cars have fully functioning setup.

mark kibort

Ericka, you should have read what i wrote. (please read this response carefully)

1. you are half right about "Pinning". you are permanently limited to the range that is available for the discs to wear. true! BUT, it has nothing to do with the split of pressure when pressure is released. this occurs ONLY by the force produced (and the control of the high mass INT plate ) via the flat springs.
this is also why the H's can move, as under high RPM, the only thing controlling the INT plate are the flat springs and the H adjusters. any vibration at all (see high rpm) will push the H adjusters back a little and cause the problem this thread is about

2. you are also Half right about the adjustment function. yes, as the discs wear, you get the pressure plate putting force on the INT plate and the forward side of the H adjusters.. this pushes them forward, if they have made contact with the INT plate due to clutch disc wear. now the gap in front is next to nothing and the gap in the rear is maxed. (all the way back basically) HOWEVER, if you push them back in a new set up, you will run into the problem the system is designed to stop. you will have TOO much gap in H adjusters, the pressure plate will not move the H forward enough to take up the rear gap, which will allow the INT plate to retreat and contact the pressure plate when you push in the clutch pedal! this is BAD BAD BAD.. please dont advise this, as it WONT work and you will cause someone to have to go back and do it all again!!!!!
do yourself and all of us a favor, read what i just wrote again and see if you agree!

Mk

christiandk

So guys,

I have adjusted the clutch on the dinner table. Now I realize why people are having such a hard time adjusting the pack while the clutch installed in the car. The H adjusters dont allow for much misadjustment in eather direction. Too far inn and the int plate wont release, too far out and the int plate wont touch the disc when compressed unless the PP presses the plate in position (all rearward technique).

Now the disc is floating nicely when the int plate is not compressed - 1mm gap appx - and there is even grab everywhere when the int plate is compressed.

I will superglue the adjusters before putting the pack back to avoid them going out of adjustment.

IF this works it has to be the easiest way to adjust the clutch properly with the pack in the livingroom

To be continued..........

P.S. if it works the method will be named the "smart guys method" because most of you are....well smart guys. If it doesn work I will earase this post

Ad0911

Well, I've been staring at my clutch assembly, sitting outside on the pickñick table, wondering how this adjusing of the H adjusters works, and frankly, I haven't got a clue. I will have to take some lessons in clutchology before I undertand this. I can't find anything adjustable. Everything seems to be spring loaded.

christiandk

Press H adjusters up/rear like this.

Pres H adjusters down/forward like this.

mark kibort

Sounds like you get it. I don't see any problem doing it this way.... You understand the basic concept of its function. Yes, if you push them all the way rearward, the disc wont touch the flywheel, but as many have said, upon installation, the pressure plate will force the H's very easily forward, but here will be no gap. (make sense Glen and others?) BUT, that means you will have a 1.5 to 2mm gap on the back side when this happens, meaning when the clutch pedal is depressed , the INT plate can travel rearward and have the rear disc touch the pressure plate surface (bad). It spins up the driveline and you will never be able to engage any gear. In Glens case and one other fellow chimed in, he had his flywheel machined, thus taking some surface height off the flywheel, thus making the distance to the pressure plate upon engagement, further..... Then it works. (at the sacrifice of pressure plate force on the flywheel, so that's why I don't advice machining the flywheel).
And yes, you have seen the distances things move are very small. but as you can see, working and not working is a .5mm change.