mariomark

Just got the car out of the second shop. New engine installed at first shop and they forgot the pilot bearing causing horrible vibrations and clutch noises. Next shop installed the pilot bearing but vibrations persisted felt mainly in the gearshift seeming to go up and down in your hand. PICO test revealed engine area as culprit with vibrations at 1900 and 4000. They just replaced the harmonic balancer, flywheel and pressure plate on the cars third visit. Vibrations are lessened at 4000 but seem greater at 1900 which is where my engine stays in the RPM range while driving. I feel this may be worse than before as there are constant higher vibrations while just cruising instead of just hitting them at 4K. My question is why do these vibrations exist in the first place and why can they not get rid of them. Are there methods used to balance the flywheel like offset locating pins or something? Is there an art to this or should it all bolt up and be balanced on assembly? I am concerned the new engine is in peril short or long term or maybe even the cause.

Dcasole

So obviously this is not normal and my guess would be that running without a pilot bearing/bushing somehow damaged your gearbox mainshaft , it does not take much runout to cause this issue

I do not believe its the engine
Dave

mariomark

That was my thinking initially, when I started leaking trans fluid I was certain it was the shaft shaking the gearbox so much it loosened the bearing and seal. Turns out it was a just a leaking fitting and the PICO did not show the gearbox to be the source of the vibes. The PICO says it is the engine. I'm flummoxed.

Dcasole

Were did the engine come from ? Was it a crate motor or was it used . Anything that is rotating is suspect , PICO is measuring the frequency of the vibration but it's not 100% ...

I am just having a hard time believing that after running without a pilot bearing , that there was no damage to torque tube shaft or bearings . Did they use the GM procedure for tightening the shaft so you dont have thrust bearing issues??

I had my motor replaced with a new crate motor after dropping a valve sonI know the stress you are under , I don't have any vibrations ... done by a dealership , and a 20 year Corvette trained technician . He took the time to talk to me about the work he was doing and why

Dave

mariomark

Dave, it was a new crate motor ordered by the dealership and installed by a GM tech. Only GM techs and myself have laid a wrench on my car. My wrenching was only fluids, brakes, wheels. I agree with the torque tube being likely damaged but they are not seing that. I just dropped it back off at the dealer. They say it will be an engine warranty issue and will be submitted to GM. As for the stress, I am just fine other than the inconvenience. Many folks wish they had my problems. Grand scheme of things this is just a bump in the road. I just cannot stand not being able to figure this out. That is what is vexing me and pushing me to ask for peoples time and knowledge to help for which I greatly appreciate. We'll have to wait and see what they want to do next.

Dcasole

Good Luck Mario and keep us posted !

Dave

Zjoe6

Was wondering if you made any progress since it's been a couple of months.

k24556

With a pilot bearing missing, the clutch disc may have been damaged. Also, the pressure plate has 3 wear compensators. A wobbly clutch disc can mess them up. I think the first shop owes you a new clutch assembly. at the least. DCAsole mentioned TT damage as well. All would give a 1X vibration to engine rpm,

The first shop should own the issue. There is no guarantee a crate engine is balanced, and shipping can mess stuff up too. I sent a diff to RTK to upgrade, and FEDEX managed to bust the case with a fork lift. Sometimes those guys can bust an anvil with a feather.

A good pico user familiar with the Pico NVH kit can see amplitudes and frequencies, and should be able to do more. Usually the tech will just put the transducer on the top of a seat stud, which is not at the center of the driveline. A better approach is to glue washers in different locations and attach the transducer to the washer. Then amplitude will be a bit higher the closer you are to the source. A disc front-center on the engine, back center, then under on the bell housing. The transducers can work upside down. The pico uses an engine rpm input as well, rotating speed is. essential.