Kenmore 11023812100 not spinning

Hi. When I look under the machine at the motor it is spinning. The shaft goes into what looks like a transfer case and the shaft coming up out of this and into the tub is spinning. but inside the tub it does not spin. I removed the agitator and the thing under it and saw a metal shaft there that periodically moves a millimeter and stops. Something under it, what makes it move is busted I guess. I also tried to get that piece off but whatever that metal thing holding that shaft in place won't budge ... seems to need a special tool to turn because it won't move. Any help would be appreciated. Thanks in advance.