Memphomaniac

I have a 2006 Z with just over 7000 miles, and I had a bearing failure in my engine a few months ago. I have the GMPP warranty, and my local Chevy dealership replaced the LS7 with a 2012 model long block. However, since the new engine was installed, I have been feeling a vibration in the shift lever. I swear it wasn't there before. I brought it back for them to check it, and they said they compared it to another car, and that this is normal.

The vibration increases in frequency with increasing engine RPM. I can feel it when stopped and just revving the engine up from idle to about 3500 RPM, whether I have the clutch engaged or not. I can feel it more (higher amplitude) when the engine is under load. I notice it starting around 2000 RPM, it gets worse by about 2500 RPM, and then by 3000-3500 RPM it becomes more of a buzz, since the frequency is higher. You can actually see the shift lever move fore & aft - not by much (1/8 inch maybe), but enough to be a nuisance. When I'm getting on the power hard in 3rd gear starting at around 2000 RPM, I can hear the buzz in the shift lever.

I plan on taking the car back and ask for the service manager and take him for a ride to demo this problem, but I'm just wondering if anyone has any idea what the cause could be. Is it possible to mount the pressure plate incorrectly to make this happen?

Thanks for any help.

jwmgr8

My 2007 Z06 was smooth
I got a 2013 z06 in Sept. had vibration in gear shift only in 5th gear and only under load.
Also felt vibration in all gears in clutch- only in peddle.
After new transmission there is no vibration in gear shift and gears shift better. Clutch still has vibration.

Memphomaniac

I'm wondering if this could be a flywheel balance issue. When a long block is built at the Wixom plant, I don't think they run the engine prior to delivery. If there is a final balancing step that happens to the engines which are being installed in cars, this step probably doesn't get accomplished in the case of a long block.

Gary '09 C6

I believe that all the engines built at the Wixom PBC are run/tested on a balance stand
before being shipped to the BG plant for installation in the assembly process.

Memphomaniac

I would believe that for an engine being installed into a car in BG, but for a long block, which gets shipped to a dealership, I wonder if that is still the case, as it is never a complete engine.

Gary '09 C6

I agree--I thought you were referring to completed engines built at Wixom. My bad...

Matt_Kah84

Are the motor mounts tight and in good condition?

Gary '09 C6

also, is the shifter linkage tight & properly aligned ?

Memphomaniac

I exchanged a PM with an engine builder from the Wixom plant, and he mentioned the long blocks ship without a flywheel and harmonic balancer. Since the dealership likely transferred those parts form the original engine, which were balanced for the old engine, that may be the source of the vibration.

Gary '09 C6

^ so, how does your problem then get fixed ?

Memphomaniac

That's the question I need help answering. The Wixom PBC guy also said the engines are internally balanced (which included my long block), and then they are externally balanced (only complete engines - not long blocks) by adding weight to the flywheel and HB (harmonic balancer). So, using that info, if the engine is internally balanced, it would seem to me that installing a flywheel which has been balanced with the pressure plate installed and a balanced HB should make it much better, i.e. adding balanced parts to a balanced engine. But I need help from the experts on that idea.

I think I'll go back and ask the Wixom guy that question. Will post the results when I know more.

Gary '09 C6

sounds like your engine will need to come out of the car, regardless.

you may want to first inquire as to the dealer economics of this, i.e., will GM pay them to fix-it-again ?

Mark2009

Well maybe... if the flywheel and HB were balanced for the other engine, then maybe not.

If the flywheel and HB are balanced off the engine as separate parts just to get them in balance (like taking a tire/wheel off to balance it), then yes. Need to ask the Wixom guy about this; I have no idea the exact method or reason for balancing these items (other than balancing them in general).

You might examine the harmonic balancer closely, in a strong light, to see if it shows any signs of abuse (like a sledgehammer beating it on or heat discoloration from being torched to get it on... all old shadetree mechanic 'tricks').

Memphomaniac

I have a photo of the HB - no issues there. I did have another PM exchange with Don at the Wixom PBC, and he thinks that the HB could have been installed in a different rotation as compared to the crank angle, as apparently there is no key on these engines to set the alignment. He said I could try rotating the HB to see if that helps. Seems it would not be a very precise process.

The FW on the other hand does have an alignment hole with the crank. But in that case, he said I could be better off without any weights, rather than having them in the wrong location.

The next step will be to meet with the service manager and see what can be done. If they refuse to do anything, I think I'll just install a performance HB & FW which is zero-balanced.