Originally Posted by JohnPawlak

I agree, if I had to do it over again, I'd probably go with the stock pressure plate and the light flywheel. I have a new, but stock CSC and so far no problems (been about 4 months). If it fails, I'll either do the Zspeed or just go back to a stock pressure plate and keep the light flywheel.

A few other comments -

Everyone always says the light flywheels are noisy or "chatter" and although I now have had the same experience, it never made sense to me. I'm 99% sure the following it what is actually going on:

<> It's not the flywheel itself making the noise - it's the fingers of the pressure plate which are acting like half-tuning forks.

<> When the clutch pedal isn't pressed in, the CSC is not touching the end of the fingers and they are free to vibrate.

<> With a relatively heavy flywheel, even at low RPM (say 700 RPM = 11.7 RPS = 35 engine fires / sec = 29 ms between fires) the engine isn't changing speed much between fires. The heavier the flywheel, the less speed variation.

<> A heavy dual-mass flywheel is even better, as it can be tuned via. spring rate and mass choice to have no speed variation on the clutch-side of the flywheel at a particular engine speed and load. Think of it as each cylinder fire compressing the springs, which slowly (relatively) release energy and ideally completely unload just as the next engine fire comes along. The engine-side of the flywheel has a changing speed, varying 3 times a revolution in the case of a V6, but the clutch-side of the flywheel is spinning at a constant rate.

<> Since the clutch-side of the flywheel is spinning nice and smooth, there is no energy present to vibrate the clutch plate fingers.

<> Switch to a light-weight flywheel, and all of this changes. The clutch side of the flywheel is now varying in speed, and this energy can go into vibrating the pressure plate fingers which can make a racket.

<> If you do something to increase the load on the engine at idle, like say turn on the AC, the speed will vary even more, and the noise will get worse.

<> Step on the clutch pedal and the CSC moves out towards the pressure plate fingers, contacting them and stopping them from vibrating, and the noise stops.

<> If you kick up the idle a bit, and get more fires/sec, you'll get less speed variation, and less noise.

<> I think the V6 configuration also makes this worse than it would be for a straight six. V6's are inherently unbalanced. If this sounds crazy there is a nice non-technical write up at http://en.wikipedia.org/wiki/.
For a really, really technical analysis you can read the last chapter of Shigley's Mechanical Engineering Design, but this get's very deep very fast.

<> The inherent V6 imbalance is not rotational, but end to end rocking, but even so this can't help the situation. I've put light flywheels in straight sixes, and had chatter, but never to the extent this car does. I'm guessing it's the V6 vs. I6 balance.

I've been really tempted to design a chatter damper for this problem, and even have a design I think would work, but who has time to rip out the transmission every time you want to test a design variation? I also think the strange-looking secondary springs in the stock pressure plate that are not present in the JWT design are just this - springs whos sole purpose is to try to damp out the noise.

I'd love to know if someone trys stock pressure plate + JWT flywheel if the chatter is better.

Originally Posted by vqsmile

^^ Exactly, and that has nothing to do with pressure plate fingers acting as tuning forks.

EDIT: What you're actually hearing is the same noise you'd hear if you had the tranny out on a bench (with the clutch and pressure plate completely out of the picture), shifted it to neutral, and then twisted the input shaft vigorously back and forth. There is some play on the gears on that shaft, and when you make rotational (twisting) pulses on that shaft, you can hear the gears clinking and clacking as they take up the slack one way or the other. Due to the inherent pulsations of torque from a V6 engine, the same effect is occurring, although the torque is always in the same direction.

Originally Posted by JohnPawlak

So, if you were right, if you had the car running in neutral with the AC on (for some load), if you pushed the clutch in only enough to engage the release bearing (CSC) against the clutch fingers, but not enough to stop the input shaft of the trans from spinning, than you would still hear the cement mixer sound. I just tried it, and you are absolutely right - it still sounds like a cement mixer even with the CSC lightly pressed against the clutch. What surprizes me is that the rings, spacers, sync cones, gears etc. would be loose enough on the input shaft to sound like that. Is this just particular to this manual trans.? I would have guessed all that stuff goes together with just a few thousands clearance, (the last time I rebuilt a manual trans. was in the early 80's, and it was a four speed out of a Ford so I really can't remember). Is it that a few thousands clearance is still enough to make noise, or is it that that to have the many parts on the input shaft go together the assembly has to have relatively large clearance? Would heavier weight oil help? New trans? Learn to live with it? Thanks.....