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Discussion Starter #1
Moderators making this a stickey may be a good idea... it would have saved me a few grand.

Always always always have your new clutch assembly match-balanced to the stock components. GM's motors are internally balanced, but not always zero-balanced. If your motor isn't perfect GM (instead of scrapping it) just unbalanced the clutch/flywheel just enought to make it perfect.

I just had to get mine all re-done and it turns out that my stock stuff was over 8 grams off. I just got my car back tonight and it's nice and smooth again. My first go around with all this and not knowing about all the facts lead to snapped flywheel bolts and a ruined clutch.

People had told me that adding my Fidanza aluminum flywheel would cause a bit of excess vibe and that my car was normal. Well after driving it tonight... it wasn't normal. The zero-balanced LUK stuff wasn't playing nice with my motor hat wanted the 8 gram off stock stuff.

Second... if you're getting a LUK stage II or a factory clutch (LUK makes them) make sure the pressure plate is adjusted to provide full clamp load. If you don't do this the clutch can slip under hard usage... mine did. Now it's adjusted correctly and nice and firm.

So on review.... always match balance no matter what brand you're using and if you have an OEM style clutch make sure it's adjusted to provide full clamp load!

Cya,
Brian
 

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Are you still using your Fidanza aluminum flywheel? What clutch did you go with? How would you describe the vibration you were getting with the Luk stuff? Was it at idle or full throttle? Both?
 

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good to see your back on the road man, its sucks you had to be the one to test this issue but its great info for anyone thinking about this upgrade.
 

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jub jub said:
Good info. Like the service manual states, transfer the weights to the new flywheel! :cheers:
So if you do this you're fine then. Right? No matter what clutch you buy? :-?
 

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jub jub said:
Good info. Like the service manual states, transfer the weights to the new flywheel! :cheers:
So your saying I should take my assy that was 0 balanced by DTE & add the weights that are off my factory assy? I'm a little confused.
 

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So on review.... always match balance no matter what brand you're using and if you have an OEM style clutch make sure it's adjusted to provide full clamp load!
How did you match balance? Transfer balance weights?
 

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Im lost, for us newbs, what is Match Balance? Ive changed clutches many times on Japanese cars and put aftermarket clutches in them where we've doubled the HP and even trippled it, and never had to come accross anything like this. Even with Fidanza flywheels.

Dixit
 

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Dixit said:
Im lost, for us newbs, what is Match Balance? Ive changed clutches many times on Japanese cars and put aftermarket clutches in them where we've doubled the HP and even trippled it, and never had to come accross anything like this. Even with Fidanza flywheels.

Dixit
I think what they are saying is....You have your new assembly balanced to match your old, however good or bad that it might be. I may be wrong though. I'm screwed if this is the case. I bought A Spec III W/flywheel that was rebalanced by DTE to 0 and have it installed now. The old stuff is long gone so matching it is not an option. I'll find out soon.
 

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The rotating assembly is internally balanced, WITH the flywheel attatched as are alot of GM motors.

If you change the flywheel and do not "match balance" the new flywheel to the old flywheel your motor is no longer in balance. Doing this will cause annoying vibrationsin the short term. And can lead to expensive engine bearing damage in the long run.
 

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TriPinTaZ said:
The rotating assembly is internally balanced, WITH the flywheel attatched as are alot of GM motors.

If you change the flywheel and do not "match balance" the new flywheel to the old flywheel your motor is no longer in balance. Doing this will cause annoying vibrationsin the short term. And can lead to expensive engine bearing damage in the long run.
If this is the case & I'm not doubting anybody, why would all these tuners & suppliers be selling this stuff with NO mention of match balancing.
 

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LS1/LS2/LS6/LS7 engines are NOT internally balanced. They have an external harmonic balancer on the crank snout.

The manufacturing processes are so close; that piston to piston, and rod to rod differences are minimal and crank balance is almost dead on without the balancer. In fact there are no large balancing pads on the rods and large amounts of heavy metal balancing is not necessary in the crank counter weights.

However very small discrepancies require:
1. the external Harmonic Balancer.
2. In addition there is a balancing weight in the key portion of the crank snout near the external harmonic balancer and pulley. It's position must be noted and maintained when replacing these parts or disassembling the engine.
3. The flywheel and clutch system is also balanced. When changing OEM flywheel to an OEM replacement flywheel the weights can and should be interchanged to the exact same position.
4. OEM Replacement clutch packs & pressure plates are also balanced.
This is addressed in the Service Manual.

Aftermarket clutch parts are NOT addressed in the Service Manual but their installation should be addressed by the manufacturer. If not, the very minimum is that any new aftermarket parts must be balance to and with the remaining OEM parts. This is common knowledge but not well publisized and should be addressed more thouroughly by the aftermarket manufacturers.
 

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DJWorm said:
LS1/LS2/LS6/LS7 engines are NOT internally balanced. They have an external harmonic balancer on the crank snout.

The manufacturing processes are so close; that piston to piston, and rod to rod differences are minimal and crank balance is almost dead on without the balancer. In fact there are no large balancing pads on the rods and large amounts of heavy metal balancing is not necessary in the crank counter weights.

However very small discrepancies require:
1. the external Harmonic Balancer.
2. In addition there is a balancing weight in the key portion of the crank snout near the external harmonic balancer and pulley. It's position must be noted and maintained when replacing these parts or disassembling the engine.
3. The flywheel and clutch system is also balanced. When changing OEM flywheel to an OEM replacement flywheel the weights can and should be interchanged to the exact same position.
4. OEM Replacement clutch packs & pressure plates are also balanced.
This is addressed in the Service Manual.

Aftermarket clutch parts are NOT addressed in the Service Manual but their installation should be addressed by the manufacturer. If not, the very minimum is that any new aftermarket parts must be balance to and with the remaining OEM parts. This is common knowledge but not well publisized and should be addressed more thouroughly by the aftermarket manufacturers.
As usual you have the real scoop. Thanks.
Here's my situation. I bought a clutch, pp & flywheel that was balanced as a unit to zero. I did NOT transfer anything from my OEM unit. What do you think???? Thanks
 

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KCMAGS said:
As usual you have the real scoop. Thanks.
Here's my situation. I bought a clutch, pp & flywheel that was balanced as a unit to zero. I did NOT transfer anything from my OEM unit. What do you think???? Thanks
First thing does it vibrate? if it doesnt then your fine!
 

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mine was a shaker and the dealership kept telling me for 2 months and 4k miles that it will all even out :mah: yeah right :bmad: it did not shake under 3k rpm over 4k it was very bad and 5k the whole car will shake

finally had enough talked to the delaership owner and got a new clutch put in and they balanaced it right or some but it is all fine now
 

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Discussion Starter #20
OK... what I'm saying is that the GM motors don't always come exactly zero-balanced. At final assembly them may have to add little weights to the back of the flywheel to make it balance out correctly.

Now if you buy a new clutch and it's perfecty zero-balanced, but your motor was one of the ones that had a purposely un-balanced flyweel then you'll induce a vibe by installing the zero'd stuff.

If you have a custom built bottom end it'll be perfectly zero'd a zero'd clutch will be the right thing.

The real problem is the GM service manuals. They say different things depending on which section you look at and was version you have. They used to explicitly say transfer the balance weights in the exact locations ot the new flywheel in the same orientation. Then in the newest manual it specifically says DO NOT transfer weights and the new clutch comes as a balanced assembly. The tech showed this to me as we reviewed everything.

My car had a mild vibe that I could feel in the shifter and the pedals. Everyone who drove my car siad it felt fine, a real driveline vibe would rock the whole car, and the with the lighter flywheel there was going too be a bit less dampening.

I drove a bunch of other C5s and they all have some mild vibe through the handle so I wrote mine off to the aluminum flywheel. The Vibe came on at about 2500 and was all the way up the rev range.

Well then my car broke ... the bolts holding the flywheel to the crank snapped and my rear main was leaking all b/c if the mild vibe.

Now that I have the car back it's a huge difference and the car is much much smoother. Always match balance... if your stock stuff is Zero'd then you're lucky!
 
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