[pdxmike]

I've been working through the maintenance punch-list on my new (to me) 968 - so far did the belts, changed the fluids, did the variocam pads and did the timing, swapped out the engine mounts. This forum has been a great resource!

 

The car is much much smoother overall and seems to be generally running well.

 

One niggling issue is the clutch. When I got the car the clutch was VERY heavy. I had my mechanic check it out (independent P-car place that knows 944/968s), and they too thought it was heavy. It's probably got the 964 PP in it as the clutch was changed 40K miles ago (10 y ago).

 

I tightened the clutch pedal helper spring and it's made the weight a lot more bearable. I'm pretty happy, actually with weight and the engagement. It's not slipping, at all, in any gears, and there's no judder that I can feel on takeoff.  

 

What's bothering me is that I can feel the engine vibration, significantly, through the clutch on disengagement (clutch in) at any point past 2000 RPM. Basically, the pedal "buzzes" and is not 100% smooth going in or out. At idle and taking off from a stop, the clutch is completely smooth. It's the 1st-2nd and subsequent exchanges that aren't smooth. It does NOT get worse past 2000 RPM - I can still feel a "buzz" at subsequent engine speeds but isn't really any worse at higher RPMs.

 

My mechanic says the clutch feels normal. I haven't driven any other 944/968s so I don't have a reference frame for "normal." (My other car is my 914 with a brand new clutch which is so light that every time I get in it I think the clutch cable must have broken So I'm curious about what other owner's clutches feel like.

 

 

 

 

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[MCL968]

I would challenge your mechanic on this one. The proper 968 clutch is smooth as butter and very easy to drive. To be fair, I have only driven a few, so I can't speak for all 968s but I would venture to guess that you have the wrong pressure plate and that is transmitting more stress and buzz to the pedal.

 

You may want to look at the firewall while someone else is pushing the clutch and brake. You may have a crack that is allowing the clutch master cyl to contact the brakes in some way. A lot of these cars have the firewall crack and strange things happen when they crack.

 

BTW, the firewall is especially likely to crack if the wrong pressure plate is installed. Pete at RS barn is about the only place you can go to where you are certain to get the right parts. My local Porsche dealership tried to convince me to use the wrong pressure plate because that's what the book calls for. They also tried to use the same logic to sell me the wrong ignition switch.

 

There is a great thread in here about the blue and green stripe pressure plates, I suggest you read up on it if you haven't already.

 

Matt

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[94SilverCab]

Definitely sounds like Pressure Plate, but could also be the DMF coming apart (the rubber between the discs breaks down).

 

JMHO,

 

Jay

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[tejon007]

Unlike your 914 (I use centerforce dual friction clutches - which refers to two different types of friction material on the clutch disk's faces), your 968 has a dual mass flywheel.


My guess is you may have a couple potential things going on...


Possible rubber disintegrating in the dual mass flywheel.


Possibly the wrong pressure plate (no matter what color, it's probably the wrong/high pressure one).


I also had a car that had the guide tube so gummed up with friction material,actually almost "welded" on the guide tube, that it caused a very high pedal pressure to release the clutch - - and barely released the clutch enough to shift gears.


Your 968 should feel about like the 914, unless the cable is binding...even the centerforce clutch with it's higher clamping force, releases like a 968...


Just my two cents.

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[tejon007]

My guess is the rubber going away and possibly a combination of the other things...because you should not have a vibration like you described...

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[pdxmike]

OK so the consensus is "not normal." I appreciate the responses.

 

I'm going to have to look at the firewall at some point. :glare: I kind of don't want to know. If it's going, I don't have time to do a proper repair right now. 

 

The vibration isn't terrible and is a little better after having the motor mounts done (the engine is MUCH smoother with new mounts!). Sometime this summer I'll budget/schedule for a new clutch and DMF. 

 

Otherwise, this is a pretty awesome little car. 

 

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[MCL968]

Design 1 racing made a shock tower brace that had an optional brace for the clutch master cylinder. I have both on my car and the added brace made the brakes and the clutch a lot more positive.

 

After I discovered the crack, I had the firewall repaired (following the expected freak-out when I saw how much the brake booster was moving when the breaks were depressed), but the brace made the biggest difference as these firewalls were just kind of weak and flexed a bit too much under pressure.

 

The good news is a few companies are now making plates for the firewall, the bad news is they are a serious pain to install.

 

M-

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[pdxmike]

Well I put on my big boy pants and took a look, and the firewall doesn't appear cracked. There's what is probably the normal flex at the firewall at the clutch MC. The brake booster isn't moving and nothing else visibly shifts or creaks. 

 

I can see from the design how the brace that ties into the shock tower would be the way to go. I like the look of the RS Barn brace. Will add it to the punch list...

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[pdxmike]

Another question - how crazy is it just to try replacing the pressure plate and needle bearings, relubing everything, and seeing what the result is? Is it not worth saving the $1600 in additional parts (DMF, friction plate, throw out bearing) to have to do the job twice? 

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[94SilverCab]

If you're doing the work yourself, I'd say go for it. If you're paying labor to someone else, I'd say why pay twice?

 

JMO,

 

Jay

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[Waylander]

As you have had belts done I would get the balance checked as its dead easy to get the bottom one the wrong way round


It will create horrid vibration above about 1400 rpm all the way to the limiter

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[pdxmike]

Update & queries:

 

I've decided to outsource the work on this one and am waiting for the parts of my full rebuild kit, including new DMF, to arrive. Green pressure plate arrived yesterday from RS Barn; appreciate the heads up MCL968.

 

Something I've noticed:

 

The engine has an intermittent vibration issue coinciding with engine temp. Cold = minimal vibration. Hot = significantly more vibration past 3K. Not awful, just noticeable. Idle is fine cold or hot. Vibration gets worse to 4000 then no worse to redline.

 

Vibration definitely coincides with engine speed and ambient temp (better on cold mornings) and importantly, is exactly the same standing or moving, and is exactly the same in neutral vs in gear and clutch in vs clutch out.

 

New motor mounts (OEM), new timing/BB. I have not checked the belt alignment yet but have been assured by the shop that its dead on. (Yup, I've read the threads where the shop was wrong multiple times, but haven't had time to pull the covers myself). Vibes were present before the belts were done. Overall still better than pre-belt job.

 

Questions: DMF or BB, right? Does the original DMF have rubber between the discs that could be warming up and making the vibration worse? Vibration in neutral with clutch pedal down rules out torque tube? Anything else I need to have the guys look at?

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[MCL968]

Yes, the DMF is rubber sandwiched between steel, so you may be right with that assessment.

 

Neutral does not rule out the torque tube bearings, only having it in gear with the clutch depressed will neutralize the propeller shaft. If the clutch is out, the shaft is spinning, regardless of what's happening within the gearbox.

 

Checking the balance shaft belts is pretty easy, don't forget there is a little window on the bottom cover to check the lower shaft alignment, so all you really have to do is pull the top cover, get a mirror, and do some extensive advanced car yoga.

 

But, for what it's worth, I have never been in a 968 that didn't have some degree of vibration. It may be minimal, but it is still there. My wife's Lexus and my DD Volvo are far smoother and vibration free. Some must be attributed to the fact that these cars represent 1990's technology, and they have large pistons and can run up to high RPMs, so I think some vibration needs to be expected.

 

Matt

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[pdxmike]

Thanks Matt. You're right of course about the TT turning in neutral; edited my above post to reflect that I should have said clutch out (pedal down).

 

Will take a look at the BB sometime before taking it in for the clutch/flywheel job.

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[Bulti]

Those motor mounts you put in, are those OEM? Because if they are not, prepare to swap them out again.


You could measure them to know if they have collapsed (again).

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[pdxmike]

Those motor mounts you put in, are those OEM? Because if they are not, prepare to swap them out again.


You could measure them to know if they have collapsed (again).

 

Yes, they're the good ones from the dealer.

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[Bulti]

Ok, that's good to hear. My bet is on the BB too. I don't trust most mechanics with these cars, sad as it may be. And espécially when it comes to the BB.

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[MLB]

Wow gotta say i love that metallic orange, mike! Is it actually a Porsche color ?

Look forward to your report on sorting any excessive vibration

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[pdxmike]

It's a polarizing color.   Original paint is anthracite grey; previous owner had it wrapped in Liquid Copper 3m vinyl. Emphatically NOT a factory color. It's well done and very low maintenance which is a plus for a PNW daily driver. 

 

My 914 is color code 99K - copper metallic - so the pair suit each other. 

 

Still waiting on the clutch release fork which is coming over from Germany - will update after the clutch job is done. 

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[94SilverCab]

FYI, the clutch release forks has replaceable pin bearings...those forks are spendy if I recall correctly.

 

JMO,

 

Jay

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