From the Clutch Pressure Plate and Clutch Driven Plate section, just found it interesting. It seems to back up Cobra4b's quote:

"Important: When the clutch pressure plate requires replacement; the engine flywheel must also be replaced along with the clutch pressure plate as an assembly."

I can't find a balancing section in my '03? Service Information CD's though the below is from my Clutch Pressure Plate and Clutch Driven Plate section. Note how it wants you to note the position of the FW relative to the crank. If the FW/PP assembly was zero balanced it woudn't matter it's position to the crank and wether or not the new PP/FW assembly was zero balanced they wouldn't just have you swap the weights to the new one so these weights must have to do with engine balancing.

"For manual transmission applications, note the position and direction of the engine flywheel before removal. The flywheel does not use a locating pin for alignment. Mark or scribe the end of the crankshaft and the flywheel before component removal. The engine flywheel must be installed to the original position and direction. The engine flywheel will not initially seat against the crankshaft flange, but will be pulled onto the crankshaft by the engine flywheel bolts. This procedure requires a three stage tightening process.
DO NOT remove the propshaft hub or flexplate from the automatic transmission engine flywheel. The flywheel, propshaft hub, and flexplate are balanced as an assembly. If service is required, the entire flywheel assembly should be replaced.
If replacing the manual transmission flywheel, note the location of any existing balance weights, relative to the position of the flywheel locating hole. Install new balance weights into the new flywheel, if applicable. Flywheel balance weights must be installed into the new flywheel in the same location as the old flywheel. A properly installed balance weight should be installed below flush with the face of the flywheel. Two different size weights are available - 15.8 mm (0.625 in) and 25.4 mm (1.0 in). "

Let me say that I'm not trying to refute Cobrab4's quotes, I have no doubt that they are genuine. I just don't get how they could have changed their position on transferring the weights midway through production. Maybe they solved the engine balancing problems another way later on (like adding weights to the balancer, which doesn't make sense because it's not keyed either but thats a whole other thread) and figured since the OEM clutch assemblys were already zero balanced that they didnt' need to do this anymore on motors made after this change but then the only weights that would be there would be from older vehicles and they should be transferred anyway.

 

exactly how I feel... here's excerpt about the balance from the sheet I had printed out.

Engine Balancing

The 1997-2003 5.7L LS1/LS6 engine with crankshaft balancer is a balanced assembly. On manual transmission Corvette applications, the flywheel, clutch, and pressure plate is also a balanced assembly. During the powertrain build process, balance weights may be adde to the crankshaft balancer and/or flywheel as required.

In order to maintain engine/clutch assembly balance, it may be necessary to install or remove blance weights as detailed below:

Crankshaft Balancer

*Existing balancer onto existing engine: The balancer position must be marked prior to removal and installed to the original position. refer to Crankshaft Balancer Removal.
*New balancer onto and existing engine: Install the same size balance weights into the new balancer in teh same location as the old component. Refer to Crankshaft balancer Cleaning and Inspection.

Engine Flywheel

Important

The flywheel, clutch, and pressure plate are a balanced assembly and are not available as individual components. The pressure plate mounts or locates onto the flywheel via two dowl pins in the flywheel. In the pressure plate is not alligned properly onto the dowel pins and tightened down, the pins may bend and the plate may be incorrectly positioned which will effect component balance.

*Existing flywheel, clutch, and pressure plate assembly onto the existing engine: Flywheel position must be marked prior to removal and installedto the original position. Refer to Engine Flywheel Removal.

*Existing flywheel, clutch, and pressure plate onto a new engine: Remove balance weights, if applicable from the flywheel

*New flywheel, clutch, and pressure plate assembly onto and existing engine: Do not transfer or install balance weights.

*New flywheel, clutch, and pressure plate assembly onto a nwe engine: Do not install balance weights

 

The whole thing seems to contradict itself...

" it may be necessary to install or remove balance weights as ndetailed below"

"*Existing flywheel, clutch, and pressure plate assembly onto the existing engine: Flywheel position must be marked prior to removal and installedto the original position. Refer to Engine Flywheel Removal."

If it was truly zero balanced then it wouldn't matter what position the clutch was re-installed.

 

*New flywheel, clutch, and pressure plate assembly onto and existing engine: Do not transfer or install balance weights.

*Existing flywheel, clutch, and pressure plate onto a new engine: Remove balance weights, if applicable from the flywheel

These two are opposing each other... The first would seem to mean that the weights in the flywheel are to balance that seperate assembly. The second makes it seem that the weights were there to make up for the imbalanced old motor, and that w/ the nwe one you don't want the weights.

See this is why this is tough.

 

Good lord....

 

This is by far the best thread about this issue I've seen! It does not appear that we will be able to get a straight answer from the service manual. Knowing that weights are installed onto the flywheel and/or balancer (neither of which are keyed...sweet ) to balance the motor (the service manuals at least do not contradict what the weights are there to balance) it would seem to me that they should be removed and added to the new PP/FW as the older service manual states. I can't see a reason not to.

I just thank my lucky stars that I did not have weights on my stock flywheel and do not have vibration problems now.

 

Is C4C5Specialist still arounf? There has to be a definative answer to this.

 

VR has it right on the money! like he stated...if you have a built (zero balanced) motor by all means get the new clutch assembly zero balanced. If you have the run of the mill motor(pardon the pun) always "balance" the new clutch assembly to the old clutch assembly.... Wash

 

^ Then why the hell does the GM repair manual say

"New flywheel, clutch, and pressure plate assembly onto and existing engine: Do not transfer or install balance weights."

If this was the case they should have clear balancing instructions in the manuals. It's crazy that the motor isn't a properly balanced assembly.

 

The Manual is wrong

GM isnt going to ballance an engine for you to perfection on a production line car.. they get it as close as they can but it is not perfect. This is why we have to be well informed before making decisions when modding the car... cause if you are wrong, you will be the one footing the bill..

VR

 

EXACTLY! Wash

 

Installed an exedy twin disk.. no transfer of weights, no nothing.

Just installed it.

Not a hint of vibration.. just my 2 cent worth.

 

Did you have any weights on your stock setup?

 

Good question...!!!

 

First, this is probably one of the best threads in C5 tech in a long time.

I am looking down the barrel of the clutchh swap this winter so this info will help a lot. From my reading I agree with vetterdstr.
If you balance your new clutch,pp,fw to the same spec as the orginal you should be fine. I would do this even if my original has zero weights on it. Better safe than sorry

It's a pain in the *** to get to the cluches on these cars, I for one don't want to do it twice and this is the most sound procedure to avoid the vibration issue's

 

I'm glad I still have my stock stuff... will get it balanced to see if it's off.

 

I had my clutch replaced in my 02 Z06 when new. The dealer said he contacted GM and was told to transfer the flywheel balance weights. This is also what my 02 Shop Manual says to do.
When returned to me the car vibrated at certain rpms.

GM sent someone to rebalance my engine and when he saw that there were weights in the new flywheel, he removed them and declared victory. The car was much much better but I still feel some vibration at 1600, 2500 and around 4000 RPM.

On another forum, C4C5 just said last week that the flywheel weights should be transferred to the new flywheel.

What a mess!

 

God this is getting rough... LOL...So I am buying a Spec 3 clutch, to replace my stock one, what else do I need to get replaced and balanced?

 

You need to replace the SPEC III prior to installation. Good luck with that if it's your daily. That's a whole other thread though.

It should go like this from what we have determined:

Mark your stock flywheel to crank relationship. Take the stock FW and PP along with your SPEC and new flywheel to your balancer and have the old setup spun and make the new setup equal (in weight and location) to the old setup. Then install the new setup in the same orientation as the old.

This makes it very hard to yank and install in one day but well worth it IMO.

If you have vibration issues after all that then trade it in on a C6.

 

I am with vetterdstr on this one.
I undertook the suckass job of doing this in my driveway with hand tools on jackstands.
I installed my Spec III/aluminum FW and it shook like a Magic Fingers bed in a cheap motel.
After spending all weekend under the car, I ripped it all out again and had my new stuff balance matched to my old stuff. You have to balance the FW and PP together. My car has 150,000 miles and doesn't vibrate.
I look at it this way, THE STUFF IN THERE DIDN"T VIBRATE, MATCH THE NEW TO THE OLD.
You can talk abou zero balance, neutral balance, three fingered European inspired monkey balance, whatever, I am always matching my new to my old because its a sucky job and common sense and experience trumps GM service manuals.