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Dual Disc Clutch Balance Connundrum?

 
Old 04-08-2019, 10:16 AM
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Chris Lockhart
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Default Dual Disc Clutch Balance Connundrum?

'89 S4 5 speed, with an 84-86 dual disc clutch retro-grade. I'm getting ready to install the components so I decided to do a little Rennlist research to go along with the WSM. Everything I'm reading says it's critical to install the components with their marked "heavy spot" 180 degrees out from each other. Makes sense, only I don't have any markings except on the intermediate plate. The new Sachs/Porsche clutch discs have no painted mark on them. When I removes the pressure plate assembly 4 years ago, I marked it with permanent marker, and planned to use a punch to put a few dots at that point, after it was out and on the bench. Apparently I forgot to punch mark it, and after receiving some family help cleaning and inspecting parts, the permanent marker line is no longer there. So, how should I proceed? TIA,
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Old 04-08-2019, 10:53 AM
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Well if you have a jig to fit the stub shaft put a disc on it and see where the heavy spot is,
then do the other disc then put them on at opposites and see if the sfat stays put
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Old 04-08-2019, 12:27 PM
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Originally Posted by Mrmerlin View Post
Well if you have a jig to fit the stub shaft put a disc on it and see where the heavy spot is,
then do the other disc then put them on at opposites and see if the sfat stays put
I was thinking of trying to rig up something like that Stan. Thanks. Any clue on the PP? Looking at the rim where the bolt holes are there appear to be two areas where there are divots drilled that I'm assuming was taking weight off for balancing purposes. Would these divots give a clue as to where the heavy spot would be?
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Old 04-08-2019, 12:39 PM
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pp is already balanced separately

Last edited by Mrmerlin; 04-08-2019 at 03:00 PM.
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Old 04-08-2019, 02:33 PM
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So then where do I position the PP in relation to the mark on the intermediate plate?
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Old 04-08-2019, 02:56 PM
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the I plate should have 2 small alignment pins and one thicker pin,
it will only fit on the flywheel one way . same with the PP
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Old 04-08-2019, 03:52 PM
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I have every clutch balanced independently from the engine.

The absolute "best' balanced stock dual disc assembly I've every seen is off by 5 grams. The absolute worst was off 12 grams.

Most people will not notice 5 grams in a 928 engine....V-8 engines without flat crankshafts (928 engines), are technically impossible to "balance". They are balanced by adding a percentage of the weight of the connecting rod and the piston onto the rod journals....and this percentage varies according to who is doing it and what the intended use for the engine is.

In other words, all 928 engines "shake" and because of the harmonics involved, will "shake" more at certain rpms.

12 grams off on a clutch assembly will be able to be felt..

Of course, the problem with balancing the clutch assembly is....how? How does one spin the clutch assembly to figure out how far off it is? I have closely guarded, dedicated 4 cylinder (944) crankshaft (same bolt pattern as on a 928 crankshaft), which is perfectly balanced (absolutely zeroed.)

I use that crankshaft to bolt on 928 clutches and "spin" the clutches to balance them.
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Old 04-08-2019, 04:07 PM
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Greg, you have so many secret-tricks it's not even funny!
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Old 04-08-2019, 05:43 PM
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Originally Posted by SwayBar View Post
Greg, you have so many secret-tricks it's not even funny!



He told us, so it's not a secret.

Honestly, I wouldn't worry about it a whole lot.

While spin balancing (dynamic) is clearly better than 'just balancing' it (static), getting it to balance well just on an axle is going to be pretty good for any real world application.
The mass is pretty low, and the distance from center isn't very big.

As Stan noted, the PP & Int plate only go together one way.
It's the actual friction discs that have (had?) the paint dots that are supposed to be opposed.
I don't know if the manufacturer has decided that they are balanced well enough that it doesn't matter, or what.

I would simply static balance them, or at least figure out which is the heavy side, and go with that.
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Old 04-09-2019, 07:49 AM
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Originally Posted by Mrmerlin View Post
the I plate should have 2 small alignment pins and one thicker pin,
it will only fit on the flywheel one way . same with the PP
Well I guess that's my confusion Stan. There were no pins when I removed the DD clutch assembly. I had been reading about pins in the WSM and in RL threads and wondered if that was supposed to be on my setup. That makes a whole lot more sense now. I guess I need to email Roger and get some pins. Thanks Stan.

Thanks everyone for your replies. It's much appreciated.
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Old 04-09-2019, 08:49 AM
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Just my two cents, but I had two pp/intermediate setups that were identical except that one had the stepped pins and one had identical pins all around. if you have the stepped pins, no problem with the hard parts lining up. I not, take them and the discs to a engine shop and have them put on a balancer separately.
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Old 04-09-2019, 03:15 PM
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Originally Posted by WALTSTAR View Post
Just my two cents, but I had two pp/intermediate setups that were identical except that one had the stepped pins and one had identical pins all around. if you have the stepped pins, no problem with the hard parts lining up. I not, take them and the discs to a engine shop and have them put on a balancer separately.
Thanks Walt.
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Old 04-09-2019, 04:06 PM
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I have the exact same issue as I just looked at the resurfaced friction discs I bought and no marks on them on either side.

I hope you like the Spec discs a lot better than I did, as that's why I'm taking my clutch apart - to change them. Super grabby and makes the car shudder as you try and spin them against the flywheel and intermediate plate for a smooth departure. No marsailles spring in them to help take up the release and smooth it out.
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Old 04-09-2019, 04:13 PM
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Originally Posted by Petza914 View Post
I have the exact same issue as I just looked at the resurfaced friction discs I bought and no marks on them on either side.

I hope you like the Spec discs a lot better than I did, as that's why I'm taking my clutch apart - to change them. Super grabby and makes the car shudder as you try and spin them against the flywheel and intermediate plate for a smooth departure. No marsailles spring in them to help take up the release and smooth it out.
Hey Pete, I was gonna text you and see if you had or could take a pic of the pins from the intermediate plate to the flywheel , since you're the only one in our Carolinas group that also has a DD clutch. My clutch discs aren't Spec, they are Sachs, but it was good to know that the Spec was grabby. Makes me feel better about going with OEM. Lol. Thanks.
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Old 04-09-2019, 04:24 PM
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Chris it would help us if you post pictures of the parts your working with,
right now I am guessing at what your looking at and thats not a great idea for perfect advice
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