An adjustment mechanism (85) for a seal assembly (80) for a pump drive shaft (52) of a pump, the pump shaft (52) mounted for rotation about a rotation axis. The seal assembly (80) comprises a rotating seal (81) mounted for rotation with the drive shaft (52) about the rotation axis and a static seal (84) adjacent the rotating seal (81) and axially moveable relative thereto. The adjustment mechanism (85) comprises an adjustment member (87) which is axially moveable so as to cause axial movement of the static seal (84) relative to the rotating seal (81). The mechanism further includes an actuator (88) and a transmission (93) for transmitting a motive force from the actuator to the adjustment member as a result of activation of the actuator. The transmission (93) is operatively connected to the adjustment member (87) at two spaced apart couplings (98) whereby activation of the actuator causes simultaneous transmission of the motive force to the two spaced apart couplings. The actuator (88) is disposed externally of all pump parts.