Vibrations what to do?

Ok so i have a 2000 ls1 in my 944 and i have been driving it about a month now. When you are stopped and you rev slowly from idle to roughly 4k the car has a fine vibration that can be felt in the steering wheel, seat, and shifter, and it is differnt at every rpm. When you rev it up from under the hood you cant actualy see it vibrating. Also when your driving the vibration can be felt in the shifter at speeds below 60, and getting higher into the 70s and 80s ( running roughly 3000 rpm) you can feel it more around. My fly wheel and pressure plate are stock c5, and my harmonic balncer is aftermarket fbody. I read on a corvette forum that these engines when running a manual transmission must have the harmonic balancer balancer once on the car with weights on the balancer wich requires a balancer made for a manual transmission? Anyone heard of that? And does anyone have any ideas to how to pinpoint this?

Thanks

1. Balance the Fly Wheel/Pressure Plate assembly
2. Ensure your Torque tube bearings are not trashed
3. Ensure the tip of your drive shaft is not trashed.
4. Ensure your motor mounts are tight.
5. Ensure you do not have an engine misfire.

Sounds like a whole pile of work i wasnt looking to do! Haha well ill tear apart when i get my tranny. Thanks for the advice

If you have the motor mounts that are made from rubber (not solid) I'd put my money there. Mine failed and caused my vibrations like that.

I have the solid tpc motor mounts, I'm starting to think its a little bit out of tune as all of my header bolts were lose and after tightening them it got a little better, and my engine will randomly "hiccup" ( feels like every cylinder missed for a moment.) when cruising at slow speeds and sometimes at 60. Idk if I described that well, but it I'm not pulling any codes, so idk if that is a tuning issue or what that is.