Okay here is my situation.

When I drive forward, everything is smooth.
When I switch to reverse (i'm driving an automatic), and allowing the car to go back without pressing the gas .. everything is fine.

When i start applying pressure on the gas pedal while in reverse (slowly) it's all fine.

BUT when i apply more pressure, it makes a very uncomfortable Clunking sound.

Anyone have problem with this before?? Help!

Driving 2003 ES, i have about 71 K on it.