High RPM vibration?

[nearmiss]

I have an LT4/6spd with minimal mods - just B&B pipes, shorty headers, 3.90 diff gears. Whats up is that somewhere around 5K rpm and above under heavy throttle, the car feels and sounds like its going to shake itself apart. Its speed independent. Needless to say, I've been avoiding high revs, but I seriously have got to find out what's going on. Please let me know if you guys have some ideas about what this might be. Thanks for the help!

 

[grapeknutz]

I would check the front vibration damper for slipping. I beliveve they are rubber mounted and can fail causing the vibration

 

[Redmanf1]

You could have a clutch problem. Does it change any when you push the clutch in and take it up in the rpm's? Have you changed or done anything since this has started? I have know of crank's to break, stay together and vibrate as the rpm's go up.