[harsh_ride]

My 968 has a nasty vibration at idle (clutch engaged and transmission in gear, or, clutch out and transmission in neutral) that persists across the power band, though it smooths out around 1200rpm and doesn't get really bad again until over 3000rpm. My initial guess was the engine mounts; Flash suggested it might be the balance belt. Well, apparently the mounts are fine and the balance belt intact; the mechanic thinks its the clutch; it's evidently quite worn. Mine's a '94 manufactured/sold in late '93, with a bit over 95,000 on the original clutch. Probably time to replace it anyway...



1) Does this sound like normal behavior for an old clutch?



2) What's the common gestalt take on replacement clutches? OEM? Better / cheaper aftermarket? I don't autocross or drive it competitively; best is maybe a spirited romp through the Santa Monica Mountains. I also clock very few miles on the car; it's logged about 3,000 since October of 2005.



3) How big a job is the clutch on a 968? My Jeep was a nightmare (and no, I'm not going to do the clutch on the Porsche myself, just want to steel myself for the mechanic's bill), but, it's 4WD with a transfer case in the way of the bellhousing and other fun stuff...



Thanks!

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[tsj9197]

a worn friction disc shouldn't cause bad vibrations like you speak of.

unless it's to the point of pieces flying off, but i'd think you'd feel that in the pedal.

but it could be a possible sign of a failing dual mass flywheel?



i think the oem clutch is just fine.

they also make a sport version.



the 968 clutch is quite easy to replace compared to most other cars.

no tranny removal required.

just remove the cat back exhaust and there is a access panel on engine bellhousing to access the clutch and flywheel.



i just did the clutch on my nissan 4x4 so i know how that goes.

the 968 is much easier.

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[94SilverCab]

It's entirely possible that the DMF has failed. Ths will usually cause a VERY noticeable vibration through the shifter. If you are going to replace the DMF you should look into RS barns (See Banner to the Right>>>) new Lightweitgh flywheel...better performance, similar $$$.



Regards,



Jat

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[flash]

since they just did the belts, didn't the vibration go away?



if they did them right (and it is very easy to invert a pulley, have the marks all line up, and have a vibration), and it is still there, then yes, i agree, likely the DMF - usually though there is also a juddering on engagement that accompanies the vibration

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[Darth Vadar]

Or...AllGermanParts will sell you a nice new old stock LuK Dual Mass Flywheel for less than $700.00 ($635.00 a few months ago)...



Either way, it's a good deal! But... I believe the RS Barn unit will still have some vibes at around 2,200 rpms... And reve faster too!



You pays your money and takes your chances!

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[Mark]

If it is not the flywheel then it could be the balance shaft is 180 degrees out of wack. They are keyed on both sides for some reason. When mine was out of whack by 180 the vibration was so bad starting about 3-3500 rpm the heat shields were banging around under the hood from it.

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[flash]

that is exactly what happened to ron's car - the marks on the pulleys all lined up, but one shaft was 180 out - took me looking at it 3 times to finally catch what the shop had done

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[tloof]

I'm just finishing up on a complete timing belt, balance shaft belt, variocam timing chain, variocam sliders, all front seals, & thermostat replacement on my 85K mile 968 engine. While I'm at it should I consider going in and replace just the clutch disk itself since the clutch still operates just fine? (in otherwords reuse the flywheel & pressure plate that is already on it). I'm thinking that by replacing just the clutch disk itself before it wears any further that it might extend the life of the flywheel & pressure plate out to around 160-170K miles or so. What do those of you in the know think on this issue?



Also, both of my balance shafts were about 4 teeth out of phase and were causing annoying vibration above 3500-4000 rpm, so this must be a common problem on these cars. My timing belt was also streched to the max with the hydraulic tensioner maxxed out in its travel, so the timing belt was on borrowed time to be sure. I don't think any of the belts had ever been changed when I bought it with 79K miles on it (it now has 85K miles), so it should really perform WAY better now that I have done all of this work.



The balance shaft front housing o-rings were leaking oil as well (all the shaft seals were OK surprisingly).

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[flash]

replacing something before it shows signs of wear is always a good idea



this particular item should involve a test of the flywheel though - if it rebounds fine, and there is no scoring on it, or the pressure plate, then yes, i would put them right back in



obviously mark the relative positions of the flywheel and pressure plate, so you reassemble in the same orientation



i would replace the clutch fork bearings and release bearing while you are in there though



since you are disconnecting the slave cylinder to do this, if you haven't done it already, you are halfway home on getting your hydraulics up to snuff, and now would be a good time to replace the master and the high pressure line

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