sometimes when Im gettting on the highway, if i floor the pedal the car will downshift, "slip", then i hear a clunk, it kinda sounds like its coming from the rear end but I could be wrong. The car is still under warranty but it doesnt do this all of the time. sometimes it does it after driving awhile sometimes not. I really dont want to have to put a new tranny in the car after the warranty runs out. the car is a late 99 impreza wagon. please help

 

i realized today while playing in the snow, that the clunk sound I hear after my front wheels spin and the rear wheels "kick in?" sounds like the one i describe before. Is there something in the rear end that could be causing this?

 

I've heard this same sound when accelerating decently from a stop out of snow in my 4EAT. I do not know whether or not it is normal or good.