LT4 More on LT4 Clutch/flywheel

[Trance_LT4]

I just ordered a single mass aluminum flywheel and stage 2 clutch (stars brand, I think) from Doug Rippie motorsports, and will be coming this week sometime. My question is, every bit of work I get done on my car, the mechanic always complains to me afterward about the vette being "special" (read pain in the @$$).

So, when changing the clutch/flywheel in my car, is there any special things that I might be able to clue the mechanic in to?

I know about the single mass flywheels causing a rattling noise when the clutch is depressed @ idle, but other than that?

 

[69MyWay]

Hmm, you know I don't think you are going to be happy with it on such an otherwise nice car. You will need to give us full details on how it runs and drives afterwards.

One VERY important thing. Make SURE that the surface on the flywheel and pressure plate has been stone ground (little swirls going in all different direction on the contact surface). If you have a nice clean machine finish like the swirls on a record (I know, many people don't even know what a record is anymore), then the life of the clutch disc may be shortened from the first time you release the pedal. We have come to the conclusion on my excessive clutch failure with my ZF six speed and single mass conversion that it was due to the clutch disc never having seated right from day one. NOW they tell me that the stone ground flat bench surface is the only way to fly. In other words, they suggest taking the brand new flywheels and having them resurfaced, or you/your mechanic taking a DA sander to them on a flate surface (about 220 grit) and giving it a good old sanding.

Here is why I don't think you will like it (at least until you get use to it). The dual mass is a heavy mammy jammy. Auto trans cars may have a light flex plate, but the torque converter makes up for the remainder of the rotating mass. That flywheel on a street car application helps keep the momentum of the engine going and helps avoid stalling, bucking, clunking the car at low RPMs (parking lots, heavy traffic, your driveway, drivethrough restraunts, etc). When you go to the single mass, and especially an aluminum one, the rotating mass is so much less that the engine has very little incentive to keep going around and around smooth and easy. It is good for generating quick RPM (that is why you are doing it), but it will also cause you to choke and stall until you get a handle on it.

Obviously this comes from one who knows, and I installed a steel one (single mass) in place of the dual.

So, not that it is a bad thing, but be prepared to be very aggravated with it for the first 2 or 3K miles. Bed that new clutch disc in nice and easy.

Yes, they are NOISY. So, be ready as well at traffic lights to have people in cars next to you looking and pointing as they tell their passengers "hey, check out the vette next to us, sounds like he has a rod or something getting ready to shoot out the bottom of the engine" (I have had do gooders ask me to roll down the window so they could tell me just that!).

As long as you can live with this, and your mechanic knows you know that the car is going to sound terrible and drive whacky at first, then you are good to go!

 

[Trance_LT4]

Does it make that aweful noise when you're driving? What I've been told so far is its just at idle when you're out of gear, and you just gotta sit there with your foot in the clutch if you don't wanna hear it.

If you know, what causes the sound? I'm trying to think about the physics of it. Is it because without the clutch being tied to more mass (the transmission) when you're in neutral, that it and the single mass flywheel vibrate alot more? I can't picture it.

 

[69MyWay]

I can only speak of my experience with my 90. What I can tell you is that in sixth gear, or simply 4 or 5 when moving slow and just lugging at low RPM, there is significant drive train noise as a result of the single mass flywheel. It sounds like metal on metal motor mounts. I usually cure it by turning the stereo up, rolling down the window and letting the air blow and drown it out, or down shift and raise the RPM. It is basically making the same noise as what you get sitting at idle with the clutch released. Only, this noise will kind of metal on metal grind/growl at speed in gear. In other words, it is doing the same thing, but with the RPM low and radio off, windows up, you are hearing it through the drivetrain.

What does it do it? I am not sure. It is has something to do with the way the ZF input gears are cut/machined that they chatter/clatter without the dampening of the dual mass assembly.

I usually drive the car alone, so it is not a problem. It is embarrasing when I have a passenger and we are just lugging on the highway.

Like I said, you have a very nice car (1996 model). It is not so much of a big deal in my 90 as it has a much lower retail value, and most people expect it to make some noise etc.

The funny thing is, I installed the roller miniram motor, headers, etc, at the same time I went with the single mass. I drove the car open headers around the block, then to the muffler shop. Obviously I could not hear anything over the open exhaust.

When I left the muffler shop nice and quiet (well, as quiet as flowmasters and no-CATS get), I could not believe the hideous noise in sixth gear! I must have pulled over half a dozen times on the way home. Later I found out this is part of the conversion when talking with TPiS. Since that time I have just gotten use to it.

 

[Trance_LT4]

Alright, it sounds like something I won't have a problem living with. My exhaust is quite loud, and I'm the kinda guy who needs a daily driver with the poor manners of a race-car.
As for resale, I wish I could say I'll never sell it......at the moment I don't plan to. I'll be kepping this one around, gradually making it road-race only, and just getting a used Z06 when the C6s come out.

 

[69MyWay]

With that said then, you will be just fine.


I am currently looking at the Doug Rippie roll cage for the C4 myself along with some other mods to move it closer to a race car than a street machine.