RallyDogRacing

Hey All,
I wanted to ask if anyone could articulate to me how the a '90 C4 might feel with a failing DMF and or worn clutch. My car has now 163k on it, and by the records everything is original. I think that means perhaps it's even got a Freudenburg dual-mass-flywheel. Certainly I can find no metion of it's replacement in the records. So when they go bad for people (way back then...), how did it feel?

What I am experiencing is all of a sudden after a smooth driving car for the past year, my clutch is very hard to modulate when starting off from a dead-stop. Initially I was guessing that the clutch disk was at it's wear limit as it feels very, VERY grabby when cold. But now I am wondering of perhaps the flywheel is headed south as well. I get serious shudder/chatter when starting from a dead-stop, and then it's completely gone while rolling. Gears 2-5 are perfect and feel as before. 1st from a slow-roll works just fine as well. It's only from a standstill that I get shudders'ville.

As I am destined to relocate to a hot-climate here in the near future, if replacing the flywheel is going to be needed; AND I want to keep completely reliable idle & decel while using the AC... If I must replace the flywheel is there a better option than simply just replacing it with a new LUK? Something mid-weight perhaps?

DaveK

I've not had a failed DMF - however, your description matches what I've seen of DMF failures. I believe that it does make the car quite clunky / jerky / grabby from a standing start.

The easiest way to tell if your clutch is old (assuming it's not slipping) is just by the weight - new clutches are very light (as I've just discovered), and a heavy clutch means yours has been there for a while. Doesn't necessarily mean it needs replacing, but it will mean it's old.

As for the flywheel - if steady idle / no stalling is important to you (especially if you're going to be using air con as well) I wouldn't even consider using anything lighter. Go for the LUK - you can get lighter, but there is always the risk of idle / stalling issues. If that is definitely something you want to avoid then I don't think you have much choice. Some people can live with it - I couldn't.

RallyDogRacing

Hey thanks Dave! I know the clutch disk & pressure plate are original, so it seems likely that this is probably a rare case of a Freudenburg DMF lasting 160k+ miles. I guess me and the two previous owners have gotten as much as can be had from one of those units. It will however make for a pricier repair.. No complaints and I'll stick with the Luk DMF. I HATE stalling on decel!

garrett376

Your clutch disc is worn out. I've had the exact symptoms you describe on 3/4 964's! Fixed it with a new clutch disc/pressure plate/bearing. One car shuddered like crazy from a start - it was truly annoying and I can't believe how long I put up with it! Which is why on my most recent C4 widebody on first sign of a shudder or even heavy pedal, I changed it out. I could not go from a stop sign without it being really jerky. A new clutch is just wonderful... feels so light!!!

RallyDogRacing

Thanks Garrett
Hmm - so I suppose I leave the DMF alone then? My only concern is that if I get in there and confirm that it's a Freudenburg, but leave it - only to find it's failed later... Well I'll be really cheesed.

I guess it's back to the original question. What does a failed DMF feel like?

garrett376

It's been said to be noise and excessive vibration at speed and during acceleration. My old cabrio had that problem after 2,000 miles when it was new... dealer replaced it with a LUK. It doesn't sound like that is what you've got
I am sure that even if you have a Freudenburg, you can post an ad on here and someone could ship you a spare LUK they're not using... unfortunately I think I might have tossed the one that was replaced by the lightweight flywheel in the race car when I was trying to clean up everything a year or so ago... but I will check in the garage for ya'....

Gary R.

Replace the clutch and replace the flywheel if it isn't a LUK type and be done with it. Has the distributor belt been replaced? As you say "by the records everything is original" that is a time bomb waiting to go off. New belt and vent kit while you're at it!! How about seals "while you have it out"?

Chad T

The 1989 C4 single mass flywheel is always an option. As a matter of fact I actually had someone tell me they had a 1990 with the single mass so you may want to check yours before you buy one. It's between the weight of the cup clutch and DMF. I think you might need a different flywheel speed sensor to go with it though.

RallyDogRacing

I meant everything original pertaining to the clutch and flywheel. vent-kit, dizzy belt and other specific maintenance was done. For the price I paid for the car I assumed that I was going to be doing the clutch & fw at some point. As far as the while I'm in there... My list is:
1. Service the failing clutch
2. Replace original cap, plugs, rotors as well as wires (162k on the wires...)
3. Do valve adjustment
4. Replace gaskets wherever I can get to without pulling cyl heads, cyls or cracking the engine
5. Clean sludge from timing chain tensioners
6. Clean the oil from everything I can get to...

Including a couple specialty tools from pelican, then whole shabbang looks like it will run me $2100 including shipping. I figure it's 3 full days of my labor, and that's bustin' hump since I've not dropped a 964 motor nor C4 tranny before. 930 & gearbox - sure... Whole lotta Audi & gearbox - sure.. But 964 no. I figure the learning curve will eat up a fair amount of time. As will the valve adjustment.

It seems sorta silly to be that far into it and NOT replace valve seals and guides - but I would think that as soon as I pull a head then I'll have to machine something... Very quickly we're into serious rebuild territory.

I will willingly accept suggestions as to other "while you're there" efforts that aren't too expensive.

KirkF

Actually in my previous research I could not find anyone who could verify that an 89 clutch setup could be used in the later DMF transmissions. The bellhousings are different. The 1989 setup has a different flywheel, clutch plate, pressure plate, throwout bearing, starter, and as mentioned speed sensor bracket. The 89 flywheel is the same weight as the RS lightweight flyhwheel, but the pressure plate is heavier, putting the rotational mass in between the DMF and RS setups. (An error in Adrians book mistakenly listed the 89 flywheel as being 19 lbs, however it is 12 lbs.)

If I was doing your clutch job I would replace your DMF because of the mileage on it, as well as all of the rest of the clutch components. (Most have been updated since your car was built). In my mind its not worth it to risk having to drop the motor a second time because your high mileage DMF died 6 months after the rest of your clutch was renewed.

Here is a list of all the components for a 1990 DMF equipped car:

1990+ Porsche 964 Carerra 2/4 Clutch Parts


PART # DESCRIPTION #

999 113 426 41 rear main seal 1
964 114 012 02 Two - Mass Flywheel 1
999 119 017 01 cheese-hd screw (flywheel bolt) M10x1.25x62 9
999 052 169 00 ball bearing 15x50x11 1
950 114 283 00 spring washer 1
950 114 281 00 washer 1
950 116 086 06 clutch release fork 1
950 116 715 01 clutch fork bush 2
964-116-028-90 pressure plate 1
964 116 014 62 clutch disc 1
950-116-080-08 release bearing 1
964 114 143 02 starter ring 1
999 510 015 02 PP Bolts (cheese-hd. Screw M8*40) 9
950 116 813 06 clutch guide tube 1
900 270 055 02 screw M6 x 14 2
950 116 710 04 operating shaft 1
999 113 418 40 operating shaft gasket 2
999 201 339 00 operating shaft bush 1
999 201 365 00 operating shaft bush 1
950 116 725 00 operating shaft cover 1
000 043 024 00 Olista Longtime 3EP 1

The release bearing, operating shaft & related parts, guide tube, and release fork have been updated since 1990. (And of course the DMF will now be a LUK.)

Sunset Porsche in Oregon is an excellent supplier for these parts, and I found them to have the best prices for factory porsche parts.

Don't take off your heads or you will get stuck in the same swampy rebuild hell that I am in right now. Your heads will need new guides and a couple valves, and your cams will need a regrind, and you might as well cut the cylinders heads and order up new Pistons/Cylinders to update the engine with sealing rings and since you went that far you might as well do the bottom end as well and...................................



Kirk

Chad T

Good info Kirk. I actually got the idea that the '89 flywheel would be a viable alternative from reading Adrian's book.

Chad

KirkF

Well I am not positive it is impossible, but I searched online and asked on pelican and here and a couple of other sites and I never got a response from anyone who had done it. So I put it in the category of 964 urban legend.

Kirk

JasonAndreas

Actually it might not be that rare, the LUK flywheel was never installed on a C4 at the factory (even in 1994). For some reason only the C2 had major problems...

Did you get your parts back from the machine shop?

KirkF

Everything but the rocker arms shipped today.

Kirk

RallyDogRacing

So does anyone have a used Luk DMF they would like to purge from their bin-of-parts? I think I may shy away from a new DMF, as I'm handy enough to do all this labor myself. I would rather risk putting in a used part to save a bit on overall costs.

Kirk - thanks very much for the detailed parts list and the supplier recommendation. Would you have considered the starter ring a "must replace" or a "might as well"? The 930's I've worked on with friends doing this very project never had any wear issues on their starter ring.