[1][2][4] To accommodate the redesigned cylinders and the necessary alteration to the Walschaerts valve gear, the running boards had to be raised to clear the steam chests and motion.

This resulted in the gentle sweeps at either end where the running boards dropped down to the buffer beam and below the cab.

This reduced their tractive effort to 35,030 pounds-force (155.8 kilonewtons) at 75% of boiler pressure, which was set at 185 pounds per square inch (1,276 kilopascals).

The engines, as built, had flangeless wheels on the leading coupled axle, but these were subsequently also flanged as shown in official SAR dimensional locomotive drawings.

[8] In the 1930s, many serving locomotives were reboilered with a standard boiler type designed by then Chief Mechanical Engineer (CME) A.G. Watson as part of his standardisation policy.

In the case of the Class 3BR locomotive, an even more obvious visual distinction is the absence of the Belpaire firebox hump between the cab and the boiler.

At the time when the other nine began to be withdrawn from railway service, the world oil crisis of the mid-1970s had erupted and all nine were virtually snapped up by industrial users responding to the South African Government's call to save oil by using alternative sources of energy.