Dont really know what this could be, maybe some of you guys could help me.

When i free rev the car, i can rev it to whatever i want 5500+

but if im in gear driving and i get on it (under load) if i get the rpms up past 3300+ i can hear it vibrate somewhere.. not sure where though..(kinda vibrates the steering wheel)

i was thinking harmonic balancer, but then it would also vibrate during free rev right?

Anybody have an idea at what this is? just curious.