Park to reverse "ka-klunk"

Just bought a new to me 2009 prius with 50k. Love the car thus far, and am learning more and more about the hybrid stuff.

One question i do have, that the dealer didnt explain well, was the planetary transmission. specifically the noises.

Its pretty quiet, but from a cold start, and into reverse, its the really odd noise. It sounds kind of like im backing a front plastic lower air damn off the curb. Like the hard, hollow plastic ka-klunk. it never does it from park to drive, or after a while of driving from park to reverse.

Any ideas? something i need to get looked at?

 

P to R, nothing. Its the let off the brake to began gassing, it will do it. Mainly when its cold. If its been running, the same process wont make any noises. P to D cold is dead quiet.

Its like a 2 second noise. Really, a literal "ka-klunk". but its plastic, hollow sounding, not like metal or a heavy noise. if that makes any sense.

 

i always use the parking brake. i'll try it without and see what it does