The ATP Hydraulic Pump Adaptor mounts onto any B3Z or B4Z water pump taking the place of the Outer Bearing Cap (116-S19914). This adaptor includes a Hydraulic Coupling (116-S30636) which is 7/8″ 13 Tooth Splined by 1 1/8″, 1/4″ Keyway and directly couples the shaft of the water pump to the shaft of the Hydraulic Motor.