 These locomotives were unique in Australia in having Alco power units in GE Transportation Systems designed bodies, a legacy of the former Alco-GE partnership which was dissolved in 1953.Although their design originated in the United States, only two similar UM20 cab and two booster units were ever built in that country, for the Erie Railroad.The 43 class were initially used on the Main Western line from Sydney to Orange, prior to electrification of the line to Lithgow in June 1957, appearing regularly on the "Central West Express".