Toyota Repair: accelleration noise, lexus gx470, train transmission

Question
I have a 03' Lexus GX470.  I hear and feel the engine clunking when I accellerate hard.  If I lightly press gas pedal there is no noise.  I can still drive it in neutral with no noise.  Noise only occurs when I press hard on gas in gear.  Noise seems to come from front wheels wells.  Noise occurs whether I'm turning or just driving straight.  Normally noise occurs when accllerating from a complete stop or accelleration uphill.  If vehicle already in motion, most of time there is no noise, but gradually noise occurs more frequent as due to prolonged use.  Noise sounds like clunk clunk clunk, almost like gears slipping or not catching when accellerating.  Please Help. Thanx for your knowledge.

Answer
Scott,
You forgot the most important piece of information; miles, that
would help me.
This could be anything from a motor mount, slop in the drive train,
transmission, or axle shafts. Take it to a dealership (you have to anyway, I can't wave a magic wand from here) they will pinpoint it,
I would only be guessing from here.