The boiler was completely lagged with asbestos mattresses and covered with planished steel, carried on a steel crinoline structure and secured in position by stainless steel bands. The axle boxes of the leading and trailing wheels on each engine unit were equipped with roller bearings while the solid bronze coupled wheel axle boxes were fitted with Ajax grease lubrication systems. Soft grease lubrication was used throughout for the motion gear, except the piston rods, valve spindles and main crossheads which were oil-lubricated. Two four-feed sight lubricators, arranged in the cab, supplied oil to the steam chests, cylinders and the ball joint of the main steam pipes on each engine unit. The main cradle frame was carried on adjustable pivots. The front pivot was a spherical type, located on the front engine unit's frame between the driving and trailing coupled wheels, while the rear pivot was a flat oil-bath type, located on the rear engine unit's frame over the driving wheels. Each engine unit’s frames were formed of two continuous bars, long and extending from the buffer beams at the outer ends to the cross-beams over the Bissel wheels at the inner ends. The front engine unit was equipped with steam as well as vacuum brake gear, while the hind unit was equipped with steam brake gear and handbrake gear. Their Type X-17 water tenders had a capacity. In spite of initial criticisms and doubts, the unusual arrangement of water tenders which had earlier only been seen on the Kitson-Meyer locomotives of the Cape Government Railways and Central South African Railways in 1903 and 1904, proved to be very effective and was later repeated upon the introduction of the Classes GMA and GO Garratts. Photographs from the 1940s show the original water tenders with a traditional high turret, later modified to a low flat-topped turret with a hinged hatch and a curved handrail across the tank barrel. The on-board water tank on the front engine unit was only used when the water tender was temporarily disconnected from the engine at running sheds, where the locomotives had to detach and run around their water tenders to change direction. While the locomotives were still shedded at Braamfontein before the new depot at Millsite in Krugersdorp was opened, their water tenders were usually only re-attached when the engines left the depot to save space. The Class GM was placed in service on the Mafeking line out of Johannesburg which it was designed for and where they were to give more than thirty years of service.