The GH wagons were converted from the open _GY_ wagons between 1979 to 1984. About 810 were placed into service
Problems were experienced with underframes cracking with these wagons. The underframes had already been in service for 20 to 40 years.
In 1980, two sets of Gloucester Suspension Units were applied to vehicles GH 155 and GH 336. Tests were conducted to 70mph(115km/hr) but nothing further developed from the experiment. The vehicles are believed to have carried the equipment until scrapped about eight years later.
At this time no scrapping data has been collected. The class was withdrawn from service by the early 1990's. They were replaced by large numbers of bogie grain wagons built in the late 1980's. At the time of their construction they were believed to be a short term measure until finance became available for new bogie vehicles.
There were several types of GH's built. In the main, the differences apparent in later years were due to modifications caried out to improve the design.
GH 1 and 2 were the prototypes, with GH 4 onwards built to a standard 4 door hopper discharge and foldover top hatch.
Great difficulty was experienced in maintaining the brake equipment. To overcome the problem, two wagons were modifed. They had cutout ends at the handbrake end. Two brake arrangements were tried; one on GH 150 and another on GH 151. Brake equipment was tucked in under the slope sheet of the hopper. These changes were not progressed with. Instead, the four hopper discharge was reduced to a two door discharge, thereby gaining clearance for maintenance. To confuse matters, GH's were still issued to service with cutout ends despite instructions to the contrary.
Another parallel modification made was a change to the top hatch design. Initial design was "in sequence flipover" lids and later the two "barrel" hatch evolved.
Most unique was a fibreglass top that fitted directly onto the hopper as a one piece cast. This top was eventually fitted to GH 810.