Whirlpool Washer Violently shakes at start of spin cycle

I recently replaced drive ring and agitator for a diff issue I was having for this machine. Its been about 6 months since that repair and everything has been fine. Recently the washer has been knocking violently at the start of spinning. It eventually corrects itself but it sounds like the thing is going to explode when it starts to spin. Any ideas of what to look for before I decide to take this thing apart?

Anyone?? Bueller?