There were two hundred bogie grain hoppers coded GJX. The first 100 were made of aluminium and the second 100 were steel construction. The number group was initially 1 - 200.
To prevent the unwanted migration of hoppers interstate most of the class were recoded to GJF_ and the grade control apparatus (retainers) removed. The wagons converted were numbered 21 - 200.
Twenty GJX wagons were retained, with numbers 1 - 20. In the initial recoding only twenty GJX were to be retained from the number group. However later it was decided to rationalise the twenty wagons to the first twenty, 1 - 20. Some GJF wagons in the group 1 to 20 ran for a short time.
In the 1979 recoding the class was altered to VHGX.
The VHGX wagons were relettered from GJX between 1979 and 1981.
Following the standard gauge conversion of the Melbourne - Adelaide line by NRC c1995/1996, the main grain feeder lines to Portland were converted to standard gauge too. This included conversion to Dunolly, via Ararat and Maryborough. A number of VHGY wagons were also converted to VHGX for these lines.