rwj383

YES- I advise not to simply transfer balast from old fw to new.
YES- I advise to take the new clutch assy and old assy to a machinist to have the new balanced to the old. This does not mean that there will be a direct transfer of the exact same balast. You have no idea where the balance of the new assy is at. But in the end you will have an identically balanced new assy to put onto the back of the motor= no out-of-balance vibrations!!

hope this is clearer.

Robert Judd
Gen3 MS

Tree

It is clearer. Thank you.

speedyc5

Some have suggested taking the "ENTIRE CLUTCH ASSY." and having it either ZERO balanced or having it balanced to match the balance of your old assy.

I would think the clutch disc should be ZERO balanced by it's self for it's position to the flywheel and PP is not fixed, and changes every time you release the clutch.

I suggest zero balancing the clutch disc and balancing the flywheel and PP as a unit to either "ZERO" or to match your old unit. Depeding on which school of thougt you follow here. The PP will only mate to the flywheel in one position.

rwj383

Speedy- you are correct here. The machine shop would know to do this. So all you need to do is take everything down to them, explain what you have going on (that your motor is externally balanced) then they should know to balance the new fw/pp to the old.

Let us know how it all turns out!

Tree

How do you balance a clutch disc?

Tree

I was asking a rhetorical question. You can't balance a clutch disc. It's about time an engine builder (Cartek, Vette Doctors, LPE, MTI, etc.) jumped in here and gave us the benefit of their experience, It's a very important subject and there has not been satisfactory closure. A lot of opinions, some contrary to the Chevy manual, some of which will undoubtedly get people in trouble. Any professional help out there?

ArKay99

Okay, now I'm gonna add to the confusion, whith some of my own frustration. I took my 99 to a supporting tuner on this forum to have them install a new SPEC Stage3 clutch and aluminum flywheel. A set of 4:10's and a hardened output shaft was installed at the same time. When I picked up the car it vibrated like a **** as soon as you went over 2000rpm. I was told that aluminum flywheels will show up an internal engine imbalance more than a steel one, that my vibration was, 'not that bad', and to see if I could live with it. So I took it home and no, I couldn't live with it so I call them back, made another appointment, and took it to them. They told me that they don't balance SPEC flywheels, because they are zero balanced at the factory. I called SPEC and talked to tech support at SPEC and this is what I was told. SPEC flywheels and PP's are zero balanced as an assembly at the factory. You must balance the new flywheel and PP assembly to the old flywheel and PP assembly because the LS1 and LS6 engines are NOT internally balanced. The flywheel at the rear balances the rear portion of the rotating assembly and the dampner at the front balances the front portion of the rotating assembly. When I get the car back the second time, they tell me that they had my old flywheel was 25 grams off, so they balanced the new assembly to that. I get in the car and it still vibrates like a ****! It is only about 25% better! The tuner is still telling me that it is, 'not that bad', and what I am experiencing is more that likely exhaust resonance. WTF? Same exhaust before with no 'resonance'. So I tell him what SPEC told me and he says to bring it back and they will take it apart and go to a different shop. Maybe the first one messed up the balancing. :confused: :mad :crazy: :smash: :smash: :smash:
Then one more fly in the ointment. Since I had the gears put in, with all the driving back and forth to the tuner, he is almost 90 miles from me, I put the required 500 miles of 'break-in on the rear gears. So I jack up the car to drain the diff and put in the new diff oil and friction modifier they sold me and the whole underside on the drivers side above the left rear axle is coated with a spray of diff oil. Called the tuner back and he's not sure what that is, but they will look at it when I return the car for the flywheel. :eek: :mad . Right now the car is up on jack stands waiting to go down on the 5th of Jan. I'm going to change the diff oil anyway, because I don't know if my diff is dry and I have to drive it almost 90 miles. So this nightmare is just getting worse. :( :cry :eek: :cuss

DieL

not really relevant but on my c4 NOBODY in c4 tec seems to understand how to do this on the zf as well. The c4s have a dual mass flywheels which obviously cant be balanced. Even worse the shoppe thats building my stroker has no frikkin clue. This is REALLY pissing me off as well. The tuner shoppes only want to sell me their clutch package for obvious reasons and cant seem to give any straight answeres as to what i should do about the internally balanced forged asembly i have. I think GM f*king sucks sometimes. :lol:

98ISGR8

ArKay 99:
I had the exact same problem on my 98. At 2k rpm it vibrated like a ****. It was also with the spec clutchs, I had it zero balanced with flywheel and also replaced the weight and it was no good. I removed the weight and still no good. No matter what I did it would not work. Finally I got the old flywheel resurfaced and installed the factory weight back in it installed a new Z06 clutch disc and a new PP from gm and put everything back together without balancing the new PPand the vibration was almost completely gone. I could feel a little difference when I first installed it but now 1 yr latter I can't even tell.Of coarse this all cost me an extra 1000.00 dollars in labor but I got the car back and figure I will fix it when I put in a 427 :nonod:

speedyc5

I have got mine torn apart in the garage right now and I'm not sure what to do. Why is installing a clutch in these somewhere between a crap shoot and rocket science? :confused: :confused: :confused:

Why can't someone from the engine plant or somewhere clue us in on this. It has caused several members "THE CLUTCH FROM HELL" stories. I'm going to take my old assy. and new Z06 assy. to the machine shop Monday and I guess I will make a decission after that visit. I may never get to try my 4.10 gears. :eek: :eek: :eek: :eek:

I hope soon everything will be :

:party: :party:

Coolvet

bloody hell! Now I'm confused as well! RWJ says "do not 0 balance" and then he advises taking the "new assy to a machinist to have it balanced to the old assy"?

There seems to be 2 options here:
1. If the FW & PP is balanced by the factory separately from the crank assy - THEN - have the new clutch and FW balanced by itself
2. If the FW & PP is balanced by the factory as part of the entire crank assy - THEN - I have no idea how to balance a new clutch assy so that it maintains the entire crank assy in balance!!

Can anyone who really knows answer this?

CJS

"2. If the FW & PP is balanced by the factory as part of the entire crank assy - THEN - I have no idea how to balance a new clutch assy so that it maintains the entire crank assy in balance"

What RWJ383 is saying is to to take your old flywheel and PP and your new flywheel and PP to the balancing shop and have them make the new parts to exactly match the old parts.
So if your old parts are 30 grams out at some point on them, then your new parts will be made to also be 30 grams out at the same point on them. That way your new parts will "maintain" the original factory "entire crank and flywheel and PP balance".

Coolvet

OK, that makes sense now! Thanks

corvettebob1

OK, I been following this for some time and I have to interject my .02.
GM uses an external balance on the engine regardless if it's an automatic or a manual.
The only difference is the manual is balanced with the pressure plate attached to the flywheel.
That's what the holes are around the perimeter of the fw are for, these pins balance the pp to the rotating engine mass including the fw.
If you change to a zero balance flywheel you will have an engine imbalance, so the new flywheel should be balanced to the old flywheel specs.
Then you must balance the new PP to the old one and add the pins to the new fw.
The only way around this is the replace the clutch package with a factory replacement and transfer the balance pins.
Or you can balance the entire rotating engine assembly with the fw and pp attached like GM does.
Factory clutch discs are zero balance unless they are defective.
Another thing is always replace the pilot bearing when in the clutch area! I have seen more vibration complaints traced to the this then any other componet.

At any rate keep this in mind, factory pieces are all balanced within a tolerence range to keep parts interchangable.
Aftermarket parts may or may not be, so do your homework before making changes to the engine rotating mass. :cheers:

Fastguy

After dealing with a horrible vibration with the new Spec 3, I took my old flywheel and PP to the machine shop with the new Spec stuff and said "make the new one JUST like the old one. No vibration problems now, though the suck factor on swapping it twice in the driveway was very high.

speedyc5

corvettebob1

I checked my old and new flywheel and neither one has any pins in the flywheel. The original PP has one pin and the new GM Z06 PP has 4 pins. Do they balance it with pins in the flywheel and pins in the pressure plate??

It seems like most agree you CAN'T merely just zero balance the new assy.

We can send a man to the Moon but we can't change a clutch. :lol: :lol: :lol:

Fastguy

It should have pins somewhere. There will be drilled holes with pins set in and peened over that are flush.

speedyc5

And these pins are in the flywheel not the PP??

:smash: :smash: :smash:

speedyc5

Corection to corvettebob1 !!!!

I rechecked my flywheel and it does have two balance pins installed.

Thank you. If the two balance pins in the flywheel are at 9 oclock the PP has two balance pins at 6 oclock and two balance pins at 2 oclock

The new flywheel has no balance pins and one balance pin in the PP.

Final note: the flywheel had several balancing holes drilled 180 degrees from the flywheel balancing pins. My guess is the flywheel was zero balanced then the four weights were added to the PP to externally balance the engine.

So I guess I will have the machine shop duplicate the balance of the old unit.

:banghead: :banghead: :banghead: :banghead:

:confused: :confused: :confused:

Bill Curlee

ttt