mark kibort

Yep, thats what is happening, but actually not as dramatic of a change so quickly. first, it was noticebly different, but driveable. had to be more careful about putting it in 1st and reverse . 3 gear downshifts had to be clean as well.

then, after 1 race, 1 qual and the last race, it was a little worse.

I dont think it cant be fixed, and suspect its the adjustment of the intermediate plate. those dimensions in the manual must mean something, after all, with the cut out hole now in the bellhousing, I can actaully see the intermediate plate move when the clutch is depressed. It moves the entire gap that I have now on the "H"s, which is the 2.5mm you see in the pics above. the gap is supposed to be .7 to 1.5mm. the "H" adjusters move the entire pressure plate forward and back , so if its now rearward by 1.5mm too much, it might be riding on the pressure plate and rear disc now. Ill know today if that is the issue. I also bled the slave and checked for the push rod movement. its looking like its doing its job as well. (1+" of movement)

I dont understand what could change in the set up just by using a high pressure, pressure plate. the pressure plate contact ring could be closer to the intermediate plate. (also forcing adjustement so that it doesnt drag when released). I bet this is the issue. UNLESS , ive burned up a disc, and I hardly thing that is possible, as after 7 years of racing, the discs still had the white ink serial numbers showing on the disc surfaces. and, i never felt the clutch slip during the races. Of course, anything is possible with 120ft-lbs more torque.

mk

mark kibort

FIXED!
The same principal applies to the "H" adjusters in one direction as the other. DO NOT adjust the "H"s all the way rear-ward. why? because this moves the intermediate plate rearward, and it could be rubbing on the disc and pressure plate, just as it can rub on the disc and flywheel.

So, if you cant get your 928 into gear, this might be the issue. Scot has this issue right now as well.
we cut a small 1-2" inspection hole in the bell housing, which is large enough for a small screwdriver to move the "H" forward, or a large screwdriver to move the H rear-ward. This way, its easy, tap a couple of screw holes, install a small plate cover, and future checks dont require you to remove the lower bell housing.

started the car up and it was like butter! went right into 1st, reverse, without a fuss!

The reason for the bad slipping for the original clutch, could be due to this adjuster not allowing pressure on the front disc to the flywheel as well.

Thanks for all the responses. maybe the stock stuff isnt that bad after all!


mk

928autobahndreamer

Excellent to hear. Now you will just have to see if the adjustment lasts.

mark kibort

Its better than before, even with the stock clutch. Its not going anywhere! Understanding what all the components do, helped in setting it up. It took a while , but it all makes sense now. they dont move, unless they (the H adjusters) are loose. since they are not loose, there is nothing acting on the floating intermediate plate adjusters except the spring pressure, which is minimal. I dont think anyone took the time to really understand these little gysmos. the manual is right, and the 1mm gap is what is needed so that you alow for 1mm of release of the front disc off the flywheel and whatever that leaves you with for the rear disc and pressure plate. more than 1mm starts to press on the rear disc and pressure plate and makes them drag against each other spinning the drive shaft so you cant get the car in gear, unless you turn it off.

Its not black magic like it started out looking like. with the cut out, you can actually see the pressure plate move back from its own spring presure when you press the clutch pedal in. If it is too close, you run the risk of it dragging. however, too big of a gap, and it positions the intermediate plate too close to the pressure plate.

That is what I've seen, and I bet JV had this issue as well as what scot is going to see tomorrow.

mk

mark kibort

Well, scot has been dealing with a syncro issue as well as the diffuculty in getting it in gear.

WE operated early this morning on the rack, cut a small hole in the bell housing, (as its impossible to remove without removing the MSDS headers) and low and behold, YEP, a larger than spec gap in the "H" adjuster. (just like mine was set at)

So, we used a screwdriver and pressed it closed slightly, since all that adjuster is doing in the normal position, is limiting how far the intermediate plate will travel when the clutch is pushed in. With too large of a gap, the intermediate plate upon clutch engagement, can move too far to the pressure plate discs and cause draggin there.

Thats exactly what was happening, so he starts it up and slips it in reverse and 1st effortlessly! he takes it on a drive and guess what, suddenly he is able to downshift into 2nd , which he has NEVER been able to do before.

By the look on his face, did this quick fix work??

Mk

GregBBRD

There you go. Glad you figured it out. John V. would adjust his "H" pieces and they would move, after a few run groups. These adjustment pieces actually move pretty easy on a new floater plate.

Now about those holes you cut.....we're working on Porsches here.....could have you used something besides the axe?

Charley B

Actually, that's the only look I ever see on Scott's face.


Good job, Mark.

mark kibort

I dont understand how they move. Is it possible that he (JV) went too far with the "H" pads? after all, mine worked for a session without adjustment at whatever setting they ended up at, but after a race, it got a little worse. If he was using the technique of moving the pads all the way back, he might have had the issue I did. I didnt hear him chime in on pushing the pads CLOSER to the "H" pad stop and see if that works. There is some friction to move them, but when in place, there is nothing acting on the "H" adjusters except that light spring attachement.

Here is another theory of why JV might have had problems. If you push the H pad all the way back, installing the pressure plate and clamping it all down puts pressure on the intermediate plate as it travels to meet the flywheel and disc. if the H is all the way back to start, it could (depending on the disc wear) push on the intermediate plate and move it and the adjusters to the flyhweel, BUT, there would be the gap you see that i had, as it would move the intermediate plate via the "h"s and narturally keep the max distance on the rear side.

This adjustment, when done to spec, is not going to move unless it starts out misadjusted. If they are really loose, i can see an issue with quick clutch engaged high change rpm revs maybe shifting things, but thats a stretch.
Why whould you want these things to move easily? (you mentiond putting lube on them when you saw my rusty demo). you want thes things to be hard to move as you dont want them moving! If you look at the clutch action when you push the clutch in, you see the intermediate plate move rearward to relieve pressure on the flywheel It only moves back with the force of the springs of the intermediate plate, so there is no force able to move those "H" pads unless the "H" adjusters are REAL loose. I suspect that is not the issue on most problems. Interesting that Scot had the same issue and I was able to fix that in a few mins as well. (He did the hole cutting, and I think he did use an axe!! ) (although, mine was not much better , but thats what you get when you are real shade tree, and only have metwrench and dremel as your tools of choice )


Mk

hacker-pschorr

Like I said before, using my bell housing (with a much nicer hole ) I center the intermediate disc while the clutch is disengaged. This would be a real PIA with the bell housing off. Some guys use tie down / ratchet straps. I tried that, not a very settling feeling having that by your head.

As Greg mentioned, there is not much room in either direction before the intermediate disc hits one of the other discs.

I was a bit confused by the "H adjusters" since in every other thread on this topic (and there are many) they are referred to as "T adjusters"

mark kibort

Yes, that cut out is much nicer, but what do you expect with a dremel and about 50 cutter wheels that break every 2 seconds.

Scot did his, as i was all suited up for work, while he was over his head with the Air tools at CT. with that tool, i could have made some real nice cuts!

Anyway, doing the correct way, would be like the manual says. Having your cut out or mine, confirms this. All you want is a little gap (1mm or so) on the "H" (and i can understand the confusion of the "H" as the bottom cant be seen unless you study the intermediate plate) so that the intermediate plate makes contact with the flywheel and has room to move back, by only 1mm or so. Any more than this, and you risk the intermediate plate pushing on the pressure plate when the clutch is engaged. (pedal pressed in) This is, what i can see, is the problem with all the advice on adjusting the intermediate plate. The "H" limits the travel to the flyweel. Pushed too far back, and you risk the ability of the intermediate plate of putting enough pressure on the flywheel. (could be a reason for my clutch slip, but thats a guess). pushed too far to the flywheel side, and yes this could be an issue as the intermediate plate might not release from the flywheel and disc side.

Centering the intermediate plate is good, IF it moves away from both friction surfaces the same. I dont think this is the case. no need to beat yourself up on this one, as the manual is right and makes perfect sense if you understand what the mechanism is doing. If you try and center the intermediate plate and this creates a position of the H too far rear ward, you risk the ability of the intermediate to make full contact with the flywheel, as it might be stopped by the hidden "H" adjuster stops on the hidden bottom part. by just using the 1mm setting as it sits compressed, you solve the problem and give the little springs 1mm of movement to retract the intermediate plate, guranteed. In the manual, they also use the words, " if you adjust the "H" adjuster to a gap of 1mm, this alone Guarantees, proper adjustment" I think they are right!

edit: I now remember checking the space between the discs when the lever was levered back (very tough and a little dangerous with the prybar ) the pressure plate/int plate distance was greater, and this would vary by a bunch of factors. (master, slave, air in the line, pressure plate, etc) You dont want to do it this way, as if the gap is larger, as it was, you would force the "H" adjuster too far rearward, and it could cause issues, similar to just pushing it back blindly. the ONLY thing that determines the Int. plate retract, is its little springs and the "H" adjuster settings. The way to do it is as the manual says and if you think about it, it makes perfect sense. they are not going to move and it will be adjusted perfectly that way.

anyone that has a clutch issue should use this research to press down on the H adjusters and make a gap of near 1mm and button it all up. It will be perfect.
Pushing them all the way back to the pressure plate direction reward, is wrong and will cause dragging and shifting issues as i saw on mine and scots car.
I was beating mine up yesterday, so was scot and its such a relief to have the shifting improve and this problem solved!

mk

John Veninger

Anything is possible, but not this. I have adjusted this clutch properly with the stock setup when I ran the 5.0L motor. No issues. Started to run into issues with the higher pressure plate

mark kibort

So, this begs the question, how did you adjust the clutch? EVERYONE told me to just push the "H" adjusters all the way back. If there was a chance of flywheel drag, that would certainly solve that issue. and maybe with a weaker pressure plate, there would be no issue with pressure plate friction surface drag. BUT, with the higher pressure pressure plate, this might then become an issue.

you said you adjusted it ,and it went on the trailer but after a session it wouldnt go into gear. (obvious clutch drag) What technique did you use to adjust it?

mk

OBehave

[QUOTE=mark kibort;5788078]Yes, that cut out is much nicer, but what do you expect with a dremel and about 50 cutter wheels that break every 2 seconds.

Scot did his, as i was all suited up for work, while he was over his head with the Air tools at CT. with that tool, i could have made some real nice cuts!

Anyway, doing the correct way, would be like the manual says. Having your cut out or mine, confirms this. All you want is a little gap (1mm or so) on the "H" (and i can understand the confusion of the "H" as the bottom cant be seen unless you study the intermediate plate) so that the intermediate plate makes contact with the flywheel and has room to move back, by only 1mm or so. Any more than this, and you risk the intermediate plate pushing on the pressure plate when the clutch is engaged. (pedal pressed in) This is, what i can see, is the problem with all the advice on adjusting the intermediate plate. The "H" limits the travel to the flyweel. Pushed too far back, and you risk the ability of the intermediate plate of putting enough pressure on the flywheel. (could be a reason for my clutch slip, but thats a guess). pushed too far to the flywheel side, and yes this could be an issue as the intermediate plate might not release from the flywheel and disc side.

Centering the intermediate plate is good, IF it moves away from both friction surfaces the same. I dont think this is the case. no need to beat yourself up on this one, as the manual is right and makes perfect sense if you understand what the mechanism is doing. If you try and center the intermediate plate and this creates a position of the H too far rear ward, you risk the ability of the intermediate to make full contact with the flywheel, as it might be stopped by the hidden "H" adjuster stops on the hidden bottom part. by just using the 1mm setting as it sits compressed, you solve the problem and give the little springs 1mm of movement to retract the intermediate plate, guranteed. In the manual, they also use the words, " if you adjust the "H" adjuster to a gap of 1mm, this alone Guarantees, proper adjustment" I think they are right!

edit: I now remember checking the space between the discs when the lever was levered back (very tough and a little dangerous with the prybar ) the pressure plate/int plate distance was greater, and this would vary by a bunch of factors. (master, slave, air in the line, pressure plate, etc) You dont want to do it this way, as if the gap is larger, as it was, you would force the "H" adjuster too far rearward, and it could cause issues, similar to just pushing it back blindly. the ONLY thing that determines the Int. plate retract, is its little springs and the "H" adjuster settings. The way to do it is as the manual says and if you think about it, it makes perfect sense. they are not going to move and it will be adjusted perfectly that way.

anyone that has a clutch issue should use this research to press down on the H adjusters and make a gap of near 1mm and button it all up. It will be perfect.
Pushing them all the way back to the pressure plate direction reward, is wrong and will cause dragging and shifting issues as i saw on mine and scots car.
I was beating mine up yesterday, so was scot and its such a relief to have the shifting improve and this problem solved!

mk[/QU
Mark,
Just so I can get my head around this,are you saying to move the H so you have a gap of 1 mm between the H and the Plate? And are you doing this with the pedal depressed or not? Because I have been having this same problem.Thanks,
Ed

John Veninger

Devek method from years ago:

Adjusting the 928 double disc clutch center ring.
The 928 double disc clutch is superior to any other production car clutch assembly. It is small in diameter, has a large surface area, low angular momentum and is easy to modulate. However, it does have one fault. Porsche discontinued the clutch at the end of 1986 because of continuing problems with having the clutch properly serviced in the field. If the center ring is out of position, the clutch, even in the fully disengaged position, will experience "drag". This drag will cause a creep when the car is standing still, in gear and idling. The clutch drag will also cause difficult shifting and grinding in reverse gear. The other aspect of the service problem is that improper lubrication of the clutch assembly and central shaft causes poor quality engagement and early failure of parts. The Fix: To properly adjust the center ring, remove the clutch cover and disengage the clutch by using a bar against the release bearing arm. In the disengaged position, the center ring should be equal distant from the flywheel and the pressure plate. If the center ring is out of position, reposition it by moving the adjusting forks of the center ring with a screwdriver. Rotate the engine by hand to gain access to each of the three adjusting forks. Disregard the dimensions given in the 928 factory repair manual! Lubricate all of the pivot points of the pressure plate diaphragm spring with dry molybdenum disulfide spray (such as Zep product #0073). Lubricate the central shaft and release bearing guide sleeve with moly paste. This procedure will assure easy modulation of, and long service life for, the double disc clutch assembly.

mark kibort

I know there is a lot of verbage here, but to be clear, NO, do not touch the clutch pedal (you especially wouldnt want to, if you had the lower bell housing off ).

All you need to do is look at the clutch as it is bolted down . the little tops of the "H" should have a 1mm gap. almost touching. I can almost gurantee that if you pull your bell housing, the gap will be near 2mm+. you need to close it down to near 1mm. thats all you need. my pictures show what that looks like, before and after. if the gap is too big, or someone has pushed them all the way rear-ward, the pressure plate and disc now become in contact with the intermediate plate and it drags when you push in the clutch pedal. this is the problem i had, scot has had for years, and If i think about it, i had it with my old race cars as well. always a little more difficult to put into reverse than it should. by the way, this intermediate plate came from my 84 in the attic and Ive never adjusted one. my old 84 with the 5 liter engine, had a new int. plate, and it was ok, but it was a little draggie. Rich (new owner of my old 5 liter engine /clutch /85transmission, might look at this adjustment as well.

mk


[QUOTE=OBehave;5788492]