I had my engine rebuilt and installed it on my 2002 z06 a couple weeks ago. Yesterday it went to the tuner. He said that he couldn't finish the tune because there was a bad vibration over 4000rpm. He said it sounds like the torque tube. I'm thinking that it might be the clutch and flywheel. I had the ls7 clutch and flywheel on the old engine and put it back on the rebuilt engine. I torqued it down properly and used an alignment tool. Does the pressure plate have to go on the flywheel a certain way? I think I just lined up the pins.

Its tge the first time I installed a clutch nevermind an engine. I knew it was risky but I wanted to learn how to do it and this forum helped a lot.

Thanks

 

Also the pressure plate and flywheel had markings on it. I'm guessing that should have been my clue but for some reason I thought I read it didn't matter how it went on

 

Ok thanks. Just read that post. So now my question is since this is a go from factory flywheel and clutch is it already balanced? And since I have a new crank in the engine how would I know how the flywheel should be bolted on? Or is it just that the pressure plate haze to be lined up in the right position with the flywheel? I had the clutch put on the car a year ago and never had vibration. So I'm guessing it's the way I put it back on.

I know it could be the TT but since I didn't touch the TT during installation of new engine I find it hard to believe it went bad once I put the new engine in.

 

WELL,,,,,,,,,, Seeing that you have to pull the TT out to re-clock the Flywheel, I would pop the Prop Shaft out of the TT and make SURE that both rubber couplers are not damaged. Before you pop it apart, make sure that there isn't any roughness in any of the TT bearings.

Did you install a NEW PILOT BEARING?

If not, put that on your list of thing TO DO!

You can run the engine without the TT installed. Just support the rear of the engine. I ran mine when I installed my SPEC Clutch just to see if I had any weird vibes. Mine was SAT!

You may still be able to re-clock the flywheel into the old OEM position. The pin hole usually leaves a dark mark on the end of the crank and you may still be able to see it. If you can just line the BIG PIN HOLE up to the dark mark where it was when it was factory hot balanced.

Then,,,,,,,,,, I would test it before you reassemble.

IF,,, your engine still vibrates, you have a couple of options:

1. Mark each pressure plate bolt with a number. You can install small metal washers under the fasteners that hold the pressure plate to the flywheel. Run the engine up to the magic 4000 RPM mark and see if the vibration improves or gets worse. Move the washers to the next spot and repeat. When you find a spot that you get an improvement, continue to add washers until you get a satisfactory balance NOTE! You will need to install a new LONGER fastener so take that into weight consideration when you are happy with the balance.

2. Find a vibration analysis company and pay them to visit you and dynamically analyze your engine balance. He will show you exactly where and how much to add washers and you will be NATS *** ON. If you have the old OEM flywheel, you could add balance pins into the outer rim of the flywheel. IF, you can find new balance pins. Check dealers.



NOTE! If you already have pins in the outer ring, take those into consideration before you add more.

Running Engine OPEN HEADERS, 10 PM at night, shitty camera, poor light. NO VIBRATIONS!




Just CLICK on the picture to start the video!

 

Thanks a lot. I did change the pilot bearing. I have a new crank so I won't be able to reclock it onto the crank. I have the old one still but I don't think that does me any good.

Is the pressure plate plate supposed to go on the flywheel a certain way?

 

How was your new engine rotating assembly balanced?

WAS IT BALANCED and if so, how much was it balanced out to?

 

The machine shop balanced it. Not sure what is was balanced out to. I'll give him a call today.

 

hold the clutch in and put it in gear. and rev it up. if it vibrates its in your engine.

go to neutral and release the clutch. and rev it up. if it vibrates its in the tube.

 

Thanks HPS. Ill try that when I get home. I just picked the car up and dropped it off at my house and came back to work. I can def fell it when there is a load on the engine. So higher gears I feel it more.

If it vibrates in neutral can it be the clutch or has to be the tube?

 

the clutch is the link in between the engine and the tube. if your dont feel it with the clutch pushed in and in gear it's probably the tube. i say put it in gear because then you know the driveshaft isn't spinning at all.

 

ok thanks alot. ill check that out tonight.

The reading I have been doing seems to show that the ls7 flywheel and pressure plate are zero balanced and it doesnt matter how you bolt it up. So maybe it is the tube

 

You have a newly rebuilt engine with a newly balanced rotating assembly. The factory hot balance does not apply to you.
For YOUR situation, you want to have your clutch assembly as close to zero balance as possible. Straight out of the box may not be good enough. They have their own balance tolerances as manufactured.

If you still have your clutch out, flywheel and pressure plate, you should take them to a good shop, probably the folks that built your engine can do it, and have them get the clutch assembly ( flywheel and pressure plate) as close to zero balanced as possible. It may only be a little "off" and be enough to cause the vibrations you are feeling.

That is of course if you do the test and do determine that you think it could be the clutch balance causing it.

It is pretty inexpensive to have your clutch assy zero balanced, better than as delivered from the box.

Good luck.

 

Thanks alot. Makes sense. Since it was a stock rotating assembly the stock ls7 clutch balancing was good enough. But now since its an all new assembly I have to have it zero balanced.

I dont have the clutch out. I am going to put it on the lift tonight and start taking down the drivetrain. Hopefully will have it out by tomorrow.

I wanted to replace the clutch anyway since I am going to be putting down 700 plus RWHP. Do aftermarket clutches come pre balanced?

If I cant find a good clutch I can afford I will probably just have my guy balance the ls7. Funds have been depleted severely since upgrading to a 383 forged assembly and upgrading to a D1sc procharger.

Thanks for the help.

 

I would say all good clutches are "balanced" from the OEMs, but that's not really the point. It's the really small total imbalances that can cause you to feel vibration in the corvette platform, due to engine/TT/transmission setup. That is fairly unique and has unique harmonics considerations. A clutch kit "balanced" from the OEM still is zero balanced to "some" balance tolerance. It will still most likely have some small imbalance, enough to feel vibrations in the manual vette, but not other cars. So, if your engine is not stock, and has been rebuilt, by someone not mass producing engine assemblies and actually hand built it, like I hope your engine builder did, then your engine is probably balanced even better than the stock form. So you want to make sure your clutch assembly is as close to zero, better than out of the box. Make sense?

Don't worry about the reasoning for stock engine with matched clutch assembly from the GM hot balance. It doesn't apply to your current situation and will only confuse things. Once you rebuilt your engine and new rotating assembly, that went out the window. You want as close to a zero balanced clutch as you can get on your new engine. If you had the stock engine, stock rotating assembly, you would want the new clutch to be MATCHED to whatever the stock FW/PP assembly ended up being. Sometimes zero, sometimes a little out, sometimes ALOT out. Just match that balance of what you are replacing, because it would be going back on the same stock engine. That is NOT your situation.

If you are upgrading the clutch no matter what, spend the 30 or 40 bucks to get it as close to zero balanced as possible. You are risking vibrations if you don't.

 

Ok great thanks a lot. That helps me understand it much better. My machine shop specializes in high performance engines and rebuilt everything by hand. He is really really good and precise with everything. And expensive. Lol. So I'm not worried about the rotating assembly. I'm going to have him balance whatever clutch I decide.

And the vibrations ions are so bad at high load levels that the tuner was scared on the dyno and wouldn't go over 4,000 Rpms. So I have to figure the vibrations out and being back to finish the tune

 

That all sounds like a good plan.

Did you do the test as mentioned above? To expand on what HPS said, do the test sitting still, not while driving. While parked in your driveway or wherever, start and run the engine. Put the shifter in Neutral, clutch engaged (pedal out). Rev the engine and see if you have vibrations. Now keep revving and disengage the clutch (pedal in), do the vibrations change, go away, or stay the same? If the vibrations go away, it is most likely propshaft/TT related. If there is no change, and still vibrates with the clutch pedal in, then it can be related to the clutch balance. Then if you put it in gear with the clutch in, (and you are not moving) and still have vibrations, also, likely in the clutch.

That will help isolate it.

 

Just tested the car out going up to 4500rpm in neutral and also in gear holding down the clutch. No vibration either way. The car has to be under a load for it to happen. So can it still be the clutch? Or is it the TT? Thanks

 

Sounds like you have ruled out a clutch balance problem. If you had a clutch (FW/PP) balance problem, you would have vibrations in both scenarios you ran. It is also unlikely you are getting the vibrations from the spinning propshaft inside the TT, this test ruled that out also.

Notice I didn't say it rules out the TT itself. The Torque tube does not spin. The propshaft always spins at engine speed inside the torque tube. This is also different than a typical "drive shaft" that spins after the gear reductions.

So something else is going on, either in the driveline downstream from the propshaft. could be transmission, rear diff, the drive wheels themselves, a number of things. Shot in the dark, have you made sure to check for anything rubbing anywhere, exhaust pieces? Everything bolted and connected right? But you have ruled out a clutch balance or propshaft problem.

Was the car on a dyno when the tuner was noticing this? Street tuning it? Have you also driven it and only then noticed it? Try to describe in as much detail as to when you experience the vibrations and what if anything makes them go away.

 

The tuner noticed it first first on the street. He said in fourth gear when he got around 4,000 Rpms the car would vibrate. Then he took it on the dyno and same thing. He said he didn't want to test it any further because he didn't want to break anything. When I drove it home I didn't really want to test it but I had it in fourth and felt it come on at like 3700rpm and stopped.

If the exhaust isnt isn't bolted correctly and tight enough could that cause vibration? I was having trouble getting t all bolted together when I reinstalled it. I'll throw it on the lift in the morning and see if everything seems right. Thanks

 

Believe it or not, loose exhaust components or parts that end up rubbing some part of the frame or something else, can sound horrible like the car's coming apart at certain rpms. Harmonics. It would be cool if you found something like that and it was that simple. That would be a real cheap fix!

And you should definitely check everything that came apart to make sure it is back correctly and to the proper tightness. If the TT wasn't mounted back correctly, it could certainly vibrate as well. The TT is the main culprit in transferring vibrations into the interior via the shifter. The propshaft spins at engine speed inside the TT. The TT has a first mode natural frequency at around 60 Hz. So when the propshaft is spinning at around 3600 rpm, it will excite the TT. That sounds dirty don't it? This is the main reason for the fine tune external balancing after assembly. BUT, you would feel this at rest if it were induced purely from an unbalance condition. So if the TT wasn't mounted back correctly, it could certainly vibrate under different loaded conditions.

Definitely check all connections of anything that came apart from the engine swap and reinstall of the clutch.

But it's not a balance related issue.