no agitation

I have a Whirlpool Ultimate Care ll, mod. no. LSQ8500JQ0. It fills, drains and spins fine, it just won't agitate. I can turn the agitator freely by hand when the machine is not in use. During the wash cycle there is a slight clicking sound and the agitator "twitches" with the clicking sound, but doesn't actually move.
My research has indicated possibly a drive block? Any thoughts or advice would be greatly appreciated

Cheers

via no agitation
by dave222