06 MMH with clunk at ~1800 RPM
 

From a stop, when I accellerate and hit around 1800 RPM, I hear a audible clunk from the transmission. If it were a regular transmission, I'd change the fluid. It doesn't do it all the time, like when I accelerate gently. It only happens when the gas engine is running. It may have been happening before, but I really noticed it recently. 144,000 miles, otherwise rock solid.