The 900 class were the first mainline diesels operated by the South Australian Railways.

Ten were built at Islington Railway Workshops to replace steam locomotives on the heavily graded Mount Lofty Ranges.

They operated both heavy freight trains and passenger services including The Overland.

After the arrival of more powerful diesel, they were concentrated on the easier-graded lines from Adelaide to Port Pirie and Peterborough.

Withdrawals commenced in May 1979[1] with the last two withdrawn on 18 June 1985 after operating a cement train from Angaston to Dry Creek.