I thought it was my wheels and tires, but with a fresh set on there I still have a bad vibration. I'm starting to wonder if it's the driveshaft or the motor mounts. Here's what it's doing...
Very noticeable vibration while driving in any gear or while revving the engine. Engine is balanced. I can hear it rattling the headers as well. No matter what the speed, if I put it in neutral the vibration goes away. U-joints are still ok. not as noticeable on deceleration and noticeable at all engine speeds on acceleration. Trans mount is energy suspension so is the torque arm mount. exhaust is true duals but there is no contact with the undercarraige, and has a rubber mount to the floor in the back where it dumps. This problem existed with the catback too. Driveshaft is thirdgen 1LE aluminum with 20k on the joints, rear is a 10 bolt with a torsen/girdle and 3.42's/ M28 trans.
The vibration is so bad it's causing a hum/dash rattles throughout the car. it's getting aggrivating and I dont find anything on here that seems to sound like my problem. Is it possible to twist a driveshaft out of balance? I'm making around 400ish rwhp at the wheels (382 at last dyno, made some changes since).

 

does it do it sitting still?

you say it goes away when you put it in neutral, clutch in or out? what if the clutch is pushed in, but still in gear?

 

You said it vibrates when you rev it but then said the vibration goes away when you put it in neutral. Do you mean that in neutral at idle it doesn't vibrate, but does at higher rpm's? I would rule out the motor mounts. Can you hear a hum from the differential when driving it? With as much power as you have and the wider c5 wheels I might guess that it's getting ready to go and could be the problem. I think that they will sometimes cause vibrations when they're going bad. E.g. http://web.camaross.com/forums/showt...tial+vibration

I'm not familiar with the 1LE driveshaft but it could be the problem too. http://web.camaross.com/forums/showt...tial+vibration

 

Makes no difference if the clutch is pushed in or out, in gear or not. If I'm rolling and it's in gear it vibrates. However it does also vibrate in N, but moreso when rolling. I'm assuming the idle while standing still vibration is because of the cam. It should clean up after 2000 but it doesn't, it still vibrates until I roll in neutral or push in the clutch. The differential does hum but the problem seems to me to be in the front or middle more than the back.
If it's in N and I rev it then it really doesn't vibrate more than usual, but when I hit the gas a little while driving (upwards of 4000 rpm), I can still feel it. It's got me stumped.

Odd thing is that it's worse sometimes more than others. If it's cold it tends to make your teeth rattle, but after it's warmed up it isn't too bad, but still annoying. Something's gotta be wrong somewhere. Is it possible the damper could be causing the problem? Like I said the engine is balanced but I'm wondering if that could be a source because in N I dont really feel it, maybe because the vibration isn't passing to the rear of the car.

 

:rollseyes: just pop the hood and rev it from the throttle body.

 

Your not really supposed to run the stiffer trans mount with the wacked out stock motor mounts anyway. I've gone to Energy Susupension all the way around and there is more vibration just by the nature of the harder rubber.