Support casing for a differential gear of an axle and track rod assembly

A driving and steering axle (10) of an off-highway vehicle includes an attached track rod assembly (17) incorporating an actuator (18) housed in spaced apart annular mountings (24, 25) of an axle drive head casing. One mounting (25) includes a slot (41) to permit through passage of one end of the assembly with a pre-attached track rod end.