New Clutch on LT1 Causes Vibration - Team Camaro Tech
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  #1  
Old Feb 14th, 06, 11:14 AM
DanDeMann DanDeMann is offline

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Exclamation New Clutch on LT1 Causes Vibration

I recently had the clutch replaced in my 95 Z-28 (LT-1). Since I got 105k out of the factory clutch, I decided to replace it with GM parts. The clutch plate, pressure plate, all bearings were replaced and the flywheel was resurfaced. Now the car has a new and rather severe vibration whenever spun above about 4000 RPM. Severe enough to blur the mirrors and rattle the shifter, similar to my memories of Harleys. This vibe occurs in any gear, when stopped, either in gear with the clutch dis-engaged or in neutral.
I had it pulled out and inspected. Everything looks perfect, so, at my suggestion, we started the motor with only the flywheel, no clutch or transmission. Smooth as glass! Absolutely perfect, like a Lexus commercial, all the way to redline. So, replacement Genuine GM clutch and pressure plate are installed. Vibrations are back! What the hell? What are the odds of finding two imbalanced clutches, from two different sources? No one seems to know what to do. Has anyone out there ever encountered this or heard of such a thing? Any ideas? Anything? Is there someone at GM I could call? I'm going nuts! HELP!
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  #2  
Old Feb 14th, 06, 11:20 AM
eville eville is offline
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Default Re: New Clutch on LT1 Causes Vibration

You should have the cover balanced with the flywheel.
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  #3  
Old Feb 14th, 06, 11:44 AM
DanDeMann DanDeMann is offline

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Default Re: New Clutch on LT1 Causes Vibration

To be sure I understand: Are you suggesting having the flywheel balanced with the pressure plate installed?
BTW: Looked at your Camaro. Really nice, clean, purposeful. I like it!
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  #4  
Old Feb 14th, 06, 11:51 AM
eville eville is offline
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Default Re: New Clutch on LT1 Causes Vibration

Yes, take the flywheel and pressure plate to a local machine shop to be balanced. The will add/subtract weight mush like balancing a tire/wheel. It sounds to me like the assembly is out of balance. Good Luck.

Thanks for the compliment.
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  #5  
Old Feb 14th, 06, 12:40 PM
DanDeMann DanDeMann is offline

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Default Re: New Clutch on LT1 Causes Vibration

Yes, it sure does sound like the assembly is out of balance. I guess I must accept the possibility that two new assemblies would both be bad. I will look into this. I was under the impression that the flywheels on LT1s are weighted to balance the engine, I think GM refers to this as an "externally balanced" engine. So I jumped to the conclusion that secondary balancing such as you suggest would actually throw the engine balance off. But I think this is a good suggestion and I will contact some local machine shops to see what they say.
Thanks for the help.
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  #6  
Old Feb 14th, 06, 01:23 PM
rafbody rafbody is offline
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Default Re: New Clutch on LT1 Causes Vibration

The pressure plate will have a paint bloch on it and this should match up with something on the flywheel. I don't remember what is on the flywheel but I remember this from when I changed mine out at 112,xxx miles on the original clutch. I had the flywheel resurfaced as well but I went back with centerforce clutch and pressure plate.
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  #7  
Old Feb 14th, 06, 02:19 PM
DanDeMann DanDeMann is offline

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Default Re: New Clutch on LT1 Causes Vibration

Thanks rafbody. I'll look into this. I just read through the GM service manual and it makes no mention of any alignment requirements. I don't really like the GM manual as I have found that it frequently omits important details, apparently assuming that "you should know that". I don't remember seeing any paint marks, but I was not looking for them either.
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  #8  
Old Mar 27th, 06, 09:30 AM
license2ill license2ill is offline

 
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Default Re: New Clutch on LT1 Causes Vibration

I have a 93 Z28 since 2000, and I have been troubleshooting the same issue since.

I initially replaced the clutch, and pilot bushing with a pilot roller bearing.
Got in the car and said yea that will fix it, no such luck, its been about 70,000 miles later and still the problem. I don't want to mention all the other parts I have thrown into the engine to try to cure this when I was going through phases thinking it was an engine related "bog".

Only now I have a rear main leak(152k on her) so I was getting ready to drop it all and buy an entire assembly- flywheel+clutch+pp, and also a master rebuild for the T56. (ive done older 4 speeds and have documentation for T56s)

But this is by far the best lead I have ever heard of, Eville my hats off to you, because I strongly beleive this is the overlooked problem. I just recently lost my job and you might have saved me a brickload of money.

My vibration is only at take off upon letting the clutch pedal go(back up) and letting the clutch engage, she shudders and you feel it originating from the transmission. Then after the shudder the car just picks up and goes, sometimes if I rev it harder or let the clutch in really fast it's not so apparent but it's still there if you know the car like I do. But this will sometimes fail too and she'll shake more violently instead. But at higher/ cruising rpms she's fine. And when decellerating she's fine. Only on clutch engaging from a dead stop it does this. It is a semi-stock clutch, carbon/fiber linings, that's all no fancy paddles or springs. The flywheel had no signs of glazing and the PP also looked good last time I was in there.

I really must, must know DanDeMann has your problem cured??
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  #9  
Old Mar 27th, 06, 01:26 PM
DanDeMann DanDeMann is offline

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Angry Re: New Clutch on LT1 Causes Vibration

Well, I have finally found my problem, after making a very expensive mistake! Race day was upon me, and I decided the vibes weren't bad enough to break anything, so I went to the track. After about 10 laps I spun a rod bearing and am now in the process of replacing the engine. Like I said, very expensive mistake. So, with everything apart I started really looking into the balance thing. What I found was that when the flywheel was resurfaced it was not properly done, resulting in an imbalance and a wobble in the clutch! I can't be certain that this blew my engine, but what feels like a tolerable vibration to me may be a gigantic load to the crank. Don't make my mistake! Either get a new flywheel or be certain the jerk resurfacing your old one knows what he is doing.
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  #10  
Old Mar 27th, 06, 01:48 PM
Go69 Go69 is offline
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Default Re: New Clutch on LT1 Causes Vibration

I work at a transmission shop and we have had a similar experience when replacing clutches on the LT1, and also on the LS1's. It is imperative that you have the flywheel balanced with the clutch disc and pressure plate assembled as a unit. Then you must be certain to reinstall those components in their exact location when you put them back on the motor.

We learned this after installing an aftermarket clutch kit the customer brought to us. Now we know that when you order a Luk clutch kit-they automatically come with the flywheel and they are balanced right out of the box!

So, if you are re-surfacing your original GM flywheel-be prepared to balance the assembly. If you are going with aftermarket (like LUK) this issue can be avoided.
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  #11  
Old Mar 28th, 06, 01:30 AM
jus4funn68 jus4funn68 is offline
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Default Re: New Clutch on LT1 Causes Vibration

Since the flywheel is use to externally balance the engine, and you had the flywheel resurfaced, then the flywheel should have been marked and re-assembled to the exact same holes as it was disassembled. Sounds to me like someone just bolted the flywheel to the first set of holes that lined up. And yes, vibration that noticible in the seat is enough to destroy the engine. jmo Kevin
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  #12  
Old Mar 28th, 06, 07:02 AM
license2ill license2ill is offline

 
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Default Re: New Clutch on LT1 Causes Vibration

Wow, this might be why I developed a rear main seal leak.

I'm not sure about me not bolting it to the exact same holes they came out of on the flywheel, when I bolted her back up.

But I will say this, I bought the car having this shudder and the guy had just had the clutch replaced and took it back to the shop and they couldn't find anything wrong, anyways I bought it like this and thought to myself its prolly a bad clutch and swapped the clutch and pilot bushing. But the problem remained.

So what do you guys recommend I do if I've managed to lose which holes the flywheel was bolted up onto the crank through originally from the factory???

I dont know tho, jus4fun, I don't think there is that many holes, if I recall correctly our LT1 flywheels bolt back up only one way, the crank has a mushroom like shape too, I think, chit I dont remember.

I really want to thank you guys, you might have also saved my engine.
I'm dropping the whole thing, replacing the clutch, resurfacing the flywheel, and then balancing at a reputable shop.

Does anyone know our resurfacing limits on the LT1 flywheels, or do you recommend an entire new one instead? (LUK clutches huh!!! good tip! btw)

Damm I'm a pretty good wrencher definitely seasoned, but in the world of car craft there is always something new to learn. Thanks again everyone.
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  #13  
Old Mar 28th, 06, 08:00 PM
BillK BillK is offline
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Default Re: New Clutch on LT1 Causes Vibration

Dan,
The engine in your Camaro uses an external balance flywheel that has a weight on it. Unfortunately it is very difficult to balance one of these with the clutch bolted on because the sflywheel itself is not balanced to begin with. If you have a good digital balancer, you can spin the flywheel by itself and record the amount and location of the "unbalance", then bolt the clutch on and try to match it, but it's a pain.
As far as resurfacing the flywheel goes, if the shop used a modern flywheel grinder, its pretty hard to screw it up. The crankshaft should have a dowel pin in it to align the flywheel to the proper location. If the engine ran smooth with just the flywheel, then it is pretty obvious that the clutch was the problem.
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  #14  
Old Mar 29th, 06, 04:57 AM
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Everett#2390 Everett#2390 is offline
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Default Re: New Clutch on LT1 Causes Vibration

An imbalanced clutch is like an out-of-balance wheel/tire combo. This same action is felt about the main bearings.
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  #15  
Old Mar 29th, 06, 07:12 AM
license2ill license2ill is offline

 
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Default Re: New Clutch on LT1 Causes Vibration

BillK,

So to balance an assembly and make sure it's all working correctly what should we have the machine shop do??

Balance the flywheel, first, then attach the clutch+PP? and retry??

you say it's a pain but is it impossible?? should we ask for print-outs or something when we go back to pick it up?

I mean damm I've had this problem for years, and I definitely don't want to ever see it again, much less after I bolt her back up again after tearing her down. Is there someone else we should take the assembly to, like a truck-rig machine shop?, those guys have real deal equipment sometimes.

I'd like to see the damm thing report a 0 disbalance.
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