Crunching Noise When Shifting???

Sometimes i find that when i am slowing to a stop when i go to shift into first (while still moving) i feel a crunching like action. It feels like it is coming from the shifter ? Anyone have any ideas as to what might be causing it, or any suggestions as to what i should do to??? I haven't had a chance to stop by the dealership (away at school right now).
-Thanks for any help
PEACE