Cobra4B

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

Dan_the_C5_Man

I know that there were a few thread a while back about "internal balanced this, external balanced that, blah blah blah".

One thing anyone w/ common sense cannot argue with is;

If you balance the replacement parts to the same spec as the old parts, you can guarantee at least as good of a balance as you initially had.

Of course you might pass up the opportunity to improve on the stock balance, but considering what a pain in the a$$ it is to get to the clutch on these cars, it only makes sense to "play it safe".

Cscokd

Thanks Brian...I'm about to install a new Exedy twin with aluminum flywheel. You probably just saved me a lot of headaches. Even though the Exedy is supposed to be perfectly balanced, I will carefully mark and remove my stock stuff clutch, match balance the Exedy and install it exactly the same way the stock one was removed. Hopefully I'll have good results. Not sure I understand what the full-clamp load business is all about though.
John

pdd000

i installed mine balnced from spec. worked out ok for me

Cajundude

So, when you are ready to replace the clutch it would be good to send the old flywheel or the whole clutch assembly to the vendor, say A&A, that you are purchasing from and have the new flywheel balanced to match the old one? Am I on the right track here?

Jeff Jeff

I am going thru the same ordeal as Cobra4B with my LUK setup.

Had LUK installed with aluminum flywheel. Noticed fairly bad balance issues. Took it back to tuner, said it was normal for an aluminum flywheel to not be as smooth.

Took it back a month later as it was unacceptable. They pulled the LUK out and found it to be off balance by over 16 grams. They had it zero balanced and reinstalled. I still have the balance issue, but it is slightly better (still bad though).

My problem is I don't have the stock assembly to match balance to, so I am SOL. My options are to try and balance the engine with washers on the PP bolts, have the engine pulled and zero balanced, or get a new engine.

It really sucks, I went from a h/c car with some clutch slippage that was fun to drive to a h/c car with vibration issues that is awful to drive.

Cajundude

Well, inferred from the post above, the answer to my question is yes. It would be a good idea to send off your stuff to have it matched to the new stuff. Thanks Cobra4b for posting this as I would be pretty pissed off if I had to do the work over because of the vibration. Sorry for your misfortune.

ericdwong

Not me... I had my assembly and flywheel match balanced and it shook like a nut remover (tree nut remover like on Monster Garage that is)... I think the damn machine shop who did my match balancing screwed up though. They welded a rather large weight on the PP. It would shake at 1800 RPM which is 60 MPH in 6th gear. I took a dremel cutting wheel and cut off that weight and now all is good (thank god).

DARN just realized I shouldnt have thrown out my original press plate and flywheel now that I think about it...although my car doesnt really shake anymore..

Dan_the_C5_Man

My guess is it might be fairly difficult to find a shop that would have the ability to properly balance this stuff.. Even if the components were mounted a hair off-center when balancing would give you wildy inaccurate results..

But it's impossible to deny the logic of the "balance it to "look" like the old components that don't currently vibrate" argument.

Just one more reason to enjoy our "special" C5's, yes?

Coc5

I Went from a Stock to Spec stage 4 aluminum flywheel setup. I always heard these horror stories of vibration from you guys. I guess I'm just lucky. I did one thing that I notice that no one on here has mentioned. I actually installed the torque tube and ran it up thru the revs, BEFORE I put it all together. No issues at all.

blazeone

Sounds like the Luk's have an issue. What a PITA that is.

For the record my Exedy Single installed by MTI is perfect. I have no vibration issues or any other problems for that matter.

C54DAZ

Spec II with fidanza Zero balanced.Nothing more form the old set up and works great. No vib. Guess I got lucky too..

stano

My Exedy Hyper Single was installed by West Coast Corvettes without any issuses!

M_T_0

I would take the precaution of sending my old pp/fw combo to have the balance checked along with my new clutch (not saying to balance the new to match the old but to just check it) then at least you would know that you had a problem.


More Than Zero

Cobra4B

Ok to clear things up....

LUK's don't have a problem, it's a great clutch. Some of you just have a better balanced assembly than others. If your motor is zero'd then a new zero'd clutch will work fine. If your motor is not perfect, putting on a zero balanced assembly is going to induce vibe.

I took my stuff to the areas tom machine/driveline shop and I was charged $100 for everything. They said they were able to match the new flywheel/pp combo down to 1/1000th of a gram. I was very impressed with their abilities and professionalism.

You don't send your stock stuff out, just find a good local driveline shop.

If your stock stuff balances out zero'd then you'll just want to verify the new a/m stuff. When I started having issues I called almost all of the bigger name tuners. Most all said they never trust a clutch from the mfg and always verify zero balance if that's what they need. You'd be surprised out imperfect they can come. My new LUK stage II that was supposed to be verified Zero-d as actually 2 grams out.

Cya,
B

Dope

Yeah, it's luck of the draw. I took my stock stuff off, threw it as far as I could, and installed my Exedy single without a second thought and the car is as smooth as can be. Guess my motor was properly balanced from the factory.

Dope

FRCTony

Lets clear this up.

If the motor is internally balanced, and you replace the flywheel, pressure plate and clutch with a balanced set (matched or not) you should NOT have a problem. If you do, then either your crank pulley, rotating assembly or new clutch parts have issues.

If the motor is externally balanced as some seem to be suggesting, you are going to expect to have issues when you change the flywheel.

I'm willing to bet the original poster had a faulty/non balanced clutch assm. part(s), or was just experiencing shudder from the aluminum flywheel.

Surely someone here can verify if the LS1 is internally balanced or not.

Cobra4B

Tony you can believe what you want... the motor is supposed to be internally zero balanced, but it's not always perfect. When it's not GM messes with the clutch assembly and balancer to get it perfect.

Like I said... my stock stuff ended up balancing out at over 8 grams off. With this clutch the car ran perfectly. With the new zero balanced clutch it vibrated and the bolts eneded up breaking and my rear main seal developed a minor leak. Now I took the new clutch and had it UNBALANCED to match the 8 gram out stocker. Now the car is perfect again!

FRCTony

Cobra,

I can tell you that it is very common for people to over torque the pressure plate when using aluminium flywheels (especially Fidanza). Lotsa vibration and those bolt heads can manage to find there way to the seal.

8 grams out ain't gonna cause the bolts to snap.

Did you see the flywheel when it came out?

I learned the hard way that loctite is your friend when comes to flywheels and pressure plates.

Y2Kvert4me

My only curiosity in this discussion is how does one check the internal engine balance with it in the car? Obviously, if you know "where" it's out...the clutch/flywheel can be (un)balanced to offset that and arrive at a zero external balance...but how do you know the internal balance to begin with?

Not digging into this anytime soon, just wondering.