Washer overflows on "large load" setting?

My washer is 10 yrs old but has been an absolute work horse and still looks brand new. Recently, it started overflowing into the laundry room after I started running a load of laundry. I quickly realized it overflowed the drum and was using the overflow to dump water all over my floor. I took the panel cover off and ran some tests to prove my theory. When set to small or medium loads it does not overflow. Only when set to large loads does it do this. Is there a timer switch or relay switch that has gone bad?