Need some flywheel differences from 454 guys.

[Chevy3+3]

First of all I have a vibration/shudder from around 1600-2000 rpms. It is present in any gear. It is present in neutral with clutch pedal in or out it makes no difference. My truck was originally a th400 truck before the swap and I had no vibrations. I installed a new Luk flywheel for an '88 V30 4 speed truck. I bought a new Luk clutch kit for the '94 Chevy.

It feels like my vibration may be related to the flywheel. So my question.....is the pressure plate for the '94 balanced to be used with a '94 flywheel? The '88 454 is externally balanced and the '94 454 should be internally balanced but I didn't think it had anything to do with the pressure plate.


Any thoughts?

[100%Chevy]

As far as I know,all 454's are externally balanced.
Do you have the balanced 454 harmonic balancer on it!
Mike.

[80SPORT]

If you have the pre 90 2 pc rr main seal mark 4 motor ...verify you have the correct flywheel;the 1 pc rear main (91 up mark 5 )flywheel has a different balance....even though it bolts on ; pressure plate would be neutral balance...you could verify by pulling clutch and starting up motor with only flywheel attached

[80SPORT]

Did you install a pilot bushing in the crank ;and is the first motion shaft engaging it?

[Chevy3+3]

Yes it is a 2 piece rear main seal. I did install an oil impregnated pilot bushing. Like I said it only vibrates between 1600-2000 rpms whether it's in gear accelerating or neutral and raving engine. The new flywheel I installed had a counter weight cast into the same location of the flex plates counter weight. I checked it before I installed it. I am just starting to wonder if the pressure plates between an '88 and a '94 may be different?

[Chevy3+3]

I ordered a brand new Luk LFW102 flywheel for the application of a '88 V30 4 speed.

I also ordered a new Luke 04902 clutch kit. It actually is the same clutch kit for the '88 and the '94.

I assumed this motor is the original but I have no way of knowing. Based on how it looks and seems tired I assume it's original. But this vibration after I made the swap makes me wonder if the motor was replace or rebuilt and balanced with the old flex plate. So I may need to have the flywheel balanced to match the flexplate

[Chevy3+3]

Originally Posted by 80SPORT

If you have the pre 90 2 pc rr main seal mark 4 motor ...verify you have the correct flywheel;the 1 pc rear main (91 up mark 5 )flywheel has a different balance....even though it bolts on ; pressure plate would be neutral balance...you could verify by pulling clutch and starting up motor with only flywheel attached

I guess there could be the possibility that the flywheel was boxed wrong. The box I got had the correct part number on it but maybe it was a flywheel for a 90+ for a one piece rear main. All I know is everything bolted together great. I also ordered new flywheel bolts and torqued them to spec. Transmission is quiet and shifts great to. I guess I just need to pull the motor out and see if the flywheel and flexplate are balanced the same. I hate to do that but it's better than trashing the rear main bearing from the balance being off

[80SPORT]

You have done all the normal checks...I would pull the trans out....start it up and check for vibration...then pull the clutch...check again....then put original flex plate back and check.
A vibration that happens in 16-2000 range but goes away higher and lower almost acts like a harmonic that is building at certain rpm .Usually that is designed out of a production engine unless the balancer ring moves...but if it ran well before it should be ok;Putting the heavy flywheel on would change the potential to have have a harmonic build up...but the engine was designed to accept either flex plate or flywheel so not likely.Will be interesting to find the issue.

[Chevy3+3]

Originally Posted by 80SPORT

You have done all the normal checks...I would pull the trans out....start it up and check for vibration...then pull the clutch...check again....then put original flex plate back and check.
A vibration that happens in 16-2000 range but goes away higher and lower almost acts like a harmonic that is building at certain rpm .Usually that is designed out of a production engine unless the balancer ring moves...but if it ran well before it should be ok;Putting the heavy flywheel on would change the potential to have have a harmonic build up...but the engine was designed to accept either flex plate or flywheel so not likely.Will be interesting to find the issue.

Yea I just need time to pull it back apart. Uugghhhh! Let me ask you this.....do you think a bad motor mount could cause it? I think I have a motor mount insulator going bad. I didn't think it could cause it but maybe it could.

[100%Chevy]

Yes,a bad motor mount can cause it.
mike.