I am faced with the delema of whether to spend the $ to replace my clutch with a dual mass flywheel at approx $900 or replace the set up with a SPEC billet steel flywheel $300 & $500 clutch see:

http://www.lmperformance.com/5266/24.html

http://www.lmperformance.com/18737/24.html

Anyone have experience with these? How much trani noise did you have with a single mass flywheel?

Just having a hard time biting off $1300 for the GM set up. I noticed in the Centerforce cataloge it warns of potential trani noise.

Thanks
Ken

I had the same concerns.

My OEM flywheel was in ok shape, except for needing a re-surface. Everywhere I checked I was told that it 'couldn't be done'. My machinist was told the same and advised me of that. I asked him to TRY? He did, and proclaimed it "ok". And it has been fine to this day (aprox 10,000 miles).

Thanks for the info. My machine shop couldn't see why they couldn't try since they were taking such a small swipe.
Glad to hear your success.

This is from the ZF6 clutch/flywheel/slave/master answer thread:

The dual mass flywheel: The popular rumor is that GM used the dual mass flywheel to help quiet down the noisy ZF6 transmission. I don't know if this is true or not, but it does make sense. Another benefit of the dual mass is the amount that it slips when dropping the clutch to launch the car. The dual mass will turn probably half a rotation under power, which cushions the transmission, universal joints, and rear end from the violent hit of trying to launch the car. The downside to the dual mass is the weight (which eats up power), and that it can not be machined if you decide to replace the stock clutch. Some people have gotten away with machining the flywheel, but in my opinion they have just gotten lucky. There is no way to chuck up the flywheel in a lathe or cutting device and be sure that they flywheel is being cut true. The nature of the dual mass prevents this.

The part of the flywheel that bolts to the crank is separate from the part that the clutch disk pushes against. The pieces are connected by what amounts to a big spring.

When you bolt the flywheel to the lathe or cutting machine, you bolt it on like the flywheel is bolted to a crank. The piece that is bolted to the machine is attached to the piece you are cutting with a big spring. There is no way to control the deflection of the spring once you start the cut. If the spring allows the contact surface to move, wobble, tilt, etc... you won't have a flywheel that can be used. Some people have gotten away with it, but there is no way to guarantee it will work. How can you precision machine something that is attached to your machining tool with a big spring?

A friend of mine did the single flywheel mod and the tranny at idle with the clutch in sounded like a coffee can (metal one) with a couple of lug nuts in it shakened lightly. But with his aluminum wheel, it rev'd quickly.

I have the 4+3 thickness FW and the tranny makes the noise as well, when my rpm is 1000-1100 rpm, it is less noticeable,,, all in all it is what it is.

I put in a single mass iron flywheel that weighs twice the OEM one and it's still noisy with the blue tag.

So the weight of the flywheel probably doesn't affect it too much. The springs in the dual mass are where the magic happens.

As we speak, my 88 is on the lift at my mechanics shop getting the clutch/flywheel replaced. He's run into an issue regarding the engagement of the clutch. The last shop that did my clutch managed to really screw things up by making a makeshift slave cylinder push rod out of two doorstops welded together. We've concluded that they ran into the same problem as my current shop but rather then diagnose the problem, they simply made a longer rod and put that in.
The issue now is whether or not they used the right clutch in the first place. If anyone has their clutch apart and can measure the "thickness" of the pressure plate from the bottom of the plate to the top of the splines it might help us in figuring out what is wrong. If all else fails, I'll end up getting a clutch kit from Ecklers and see if that works.

Anybody have theirs apart?

My pressure plate measured 2.0" from surface to springs while bolted up to the flywheel I know this is hard to measure, but I figured measuring it off the car doesn't make any sense.

Others have measured theres as low as 1.8"

Clutch is about 0.33" thick.

pressure plate spring movement is about 2:1 compared to surface movement... so if the throwout bearing moves 1/2", the friction surface pulls back about 1/4".

If all else fails, head to autozone and "rent" one for comparison, then return it.

hi guys,
how are ya!
i just brough a Ram performance # 1514 ,153 tooth billet single mass 16 Lb flywheel recently.
it looks a nice piece.
i ordered it in a neutral balance to suit the engine balance first of all.
so what is the process to fit this ??, do i need to balance it up with weights to suit new clutch or not or just run it as is please ??
cheers
glen

The pressure plate should have a paint mark on the flange, line this up with the one you remove, (if it still has the mark on it).

Otherwise I wouldn't worry about it.

I can't speak for the 91 flywheel though. Does the factory one have weights that screw into it?

hi centralcoaster,
how are ya!
i thought some time ago that i heard the factory flywheel did have built in weights too it.
may be wrong though
cheers
glen

Your 91 has holes around the perimeter of the stock flywheel to facilitate balancing if necessary. Most cars don't have any weights in the holes, but do to the nature of assembly line manufacturing, some cars needed some fine tuning after they were built; those cars will have weights pounded/screwed into some of the holes.

If your 91 has no holes filled on the flywheel, the stock GM balance (which is 32 grams, not zero) was good enough. If there are holes filled with weights, you'll need to add the appropriate amount of weight in the appropriate spot on the flywheel.

If you have a neutral balance flywheel right now, it theoretically won't work without adding the 32 grams that GM put on the stock flywheel. However, in the past, I've done clutches in other cars where I replaced a counterweighted flywheel with a neutral flywheel. I never had an issue. I can't say that you won't have one, but in the past I have had success with a zero balance flywheel.