WPSR3120W2WW fills, agitates and drains but doesn't spin.

Smelled burning rubber and changed the belt. Watching the unit with the front cover off I noticed that after it drains the motor hums like it should be spinning but the belt doesn't move -but I can see the shaft with the clip spinning.

Obviously, when it agitates the belt moves.

What do I need to repair or replace on this machine the clutch, transmission etc. to get this to spin? I did replace the belt but some sites say you must replace the c-clip and possibly deal breakers like the transmission ($). Anyway if anyone could help me I would really appreciate it. I realize its old but if its easy and relatively inexpensive I'll give it a try. Thanks!