165 Co-Co 1050hp ALCO DL531 were built by AE Goodwin, Sydney between 1959-1970 for NSWGR.
The 48 Class were ordered to commence the conversion of branch lines to diesel traction with the first entering service in September 1959. Further orders saw 165 in service by October 1970. There were four versions:
Mark 1: 4801 – 4845
Mark 2: 4846 – 4885
Mark 3: 4886 - 48125
Mark 4: 48126 – 48165
The Mark 1's and Mark 2's can be distinguished from the others by their fuel tank, which incorporates the brake reservoir tanks on either side.
As well as branch lines they operated both main line and metropolitan services on every line in the state. Aside from a couple written off after accidents in the mid-1980s, withdrawals didn't commence in earnest until August 1994. In December 1994 the first Mark 1s were sold. By June 1997 FreightCorp's fleet was down to 120 units.
Others have been withdrawn since and as at January 2014, 66 remained in service primarily with Pacific National. GrainCorp, Greentrains, Junee Railway Workshop and RailCorp also operate some.