Vibration in shifter

The rep from SPEC called today and said the flywheel/PP was balanced, so that isn't the vibration issue. I am going to get my PCM programmed and send out my fuel injectors to be cleaned in the hopes it is a miss.
On the bright side, if I hadn't removed the clutch the bad slave and axle would not have been found until they failed.

Arthropraxis wrote:The rep from SPEC called today and said the flywheel/PP was balanced, so that isn't the vibration issue. I am going to get my PCM programmed and send out my fuel injectors to be cleaned in the hopes it is a miss.
On the bright side, if I hadn't removed the clutch the bad slave and axle would not have been found until they failed.

Take a close look at Missfire counts, sometimes the DTC's are disabled and you won't get any codes.
These motors are very fussy about spark, if you have bad wires, plugs, wrong AFRs or any other bad cylinder condition, misfires could manifest themselves as a vibration.
Another test would be to run the motor in the dark and look for arcing, I had this problem for months until I notices arcing on one cylinder.

As I stated in an earlier post, as I tuned my motor the vibration became less noticeable.

On the LS engines, the driver's and passenger side head have to be grounded or misfires will happen.

xschop wrote:On the LS engines, the driver's and passenger side head have to be grounded or misfires will happen.

Would the pcm throw a misfire code if this were happening?

The flywheel and PP were pronounced balanced by Spec. They were reinstalled, with a new C5 slave cylinder, PCM retuned, fuel injectors cleaned, ground strap added to the drivers side head, new drivers side axle and transaxle fluid. The car is running smoother, cooler and no chatter at all from the clutch which was an issue prior to all of this work. There is no change with the vibration in the motor/shifter.

The vibration can be felt through the seat and gas pedal if held at 3K RPM. The crank pulley/damper is the only other external item I can think of that could cause this. The motor did come out of a wrecked car. Anyone have any other ideas?

What do the cylinder head ground straps look like?

a braided wire without insulation either copper or stainless steel

Braided metal of some sort on the drivers side, I may get another one for the passenger side. The passenger side is grounded to the body through the Neg battery cable.

I may have found the cause of my vibration. The vibration damper/crank pulley inner hub is not flush with the outer ring. On one side the inner hub sits below the outer ring, 180 degrees on the other side the inner side sits above the outer ring.

Could someone kindly show pics of the ground straps. Thanks.

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Was the damper ever removed? I hope this is it, you went through a lot so far!

Sorry I meant pics of where they go, I don't see any on my engine, I guess my heads are grounding through the studs.

There are screw holes in the heads front and back that are unused. Attach one end to one of those and the other end to a bare metal or one of the factory ground locations.

Arthropraxis wrote:I may have found the cause of my vibration. The vibration damper/crank pulley inner hub is not flush with the outer ring. On one side the inner hub sits below the outer ring, 180 degrees on the other side the inner side sits above the outer ring.

Fingers X'd that this is the problem!

87-944S wrote:Was the damper ever removed? I hope this is it, you went through a lot so far!

The motor came out of a wreck, no way of knowing if the damper was changed. It looks factory.

Check the damper bolt, a new one should be used if you undo the bolt. Torqueing the bolt is tricky because you pre-load the bolt at a set torque then continue turning the bolt a given number of degrees,

fliermike45 wrote:Check the damper bolt, a new one should be used if you undo the bolt. Torqueing the bolt is tricky because you pre-load the bolt at a set torque then continue turning the bolt a given number of degrees,

Thanks, I read through the procedure to remove and reinstall the pulley. Sounds like fun.

Arthropraxis wrote:
Thanks, I read through the procedure to remove and reinstall the pulley. Sounds like fun.

Ha! I have an oem-sized replacement pulley (my present one is under-sized) that I've had since about last September that I've not installed yet. Not a fun job from what I've read...

I need your lift, that would make it easier.

Come on down! It hasn't had a car on it for 4 days. It feels lonely...

I found some new info. The Corvettes with a manual trans have the flywheel and vibration damper "hot balanced" essentially they add weight to smooth out the vibrations. If you put on a zero balanced flywheel then vibrations may be experienced but it is in tolerance for the motor. I am still going to replace the damper just to make sure. Here is the link http://forums.corvetteforum.com/c5-tech/2981621-necessary-to-balance-ls7-clutch-pp-flywheel-2.html

Thanks Anthro. So if you don't have your original PP/FW/harmonic damper to use to match balance, there is really no way to ensure balance?

acorad wrote:Thanks Anthro. So if you don't have your original PP/FW/harmonic damper to use to match balance, there is really no way to ensure balance?

It would seem so. The vibrations won't cause any damage, per the thread citations. It is interesting that the only combination that I found to this procedure performed on is the Corvette which uses a torque tube and transaxle similar to the 944.

The car still has the vibration and I didn't look for anyone local that can do the hot balance, it may still be a tuning issue. I read that removing or not installing the preload plates on the Energy Suspension motor motor mounts can elimiate or decrease the vibration. If anyone else is having this problem that is one more item to check.