A slack adjuster having a single, unitary housing that changes in length to compensate for brake pad wear in a rail car braking system. A threaded tension rod extends a variable length from the housing depending on rotation of the tension rod relative to the housing. A clutch assembly enclosed within a rod guide controls rotation of the tension rod and an overtravel assembly positioned in the single housing controls whether the clutch assembly will allow or prevent rotation of the threaded rod. A control rod and actuating tube transmit the controlling forces to the overtravel assembly so that the tension rod will be retained in a new length when the slack adjuster needs to take up slack in the braking system.