Ordered in 1952 to provide motive power for the newly electrified Penrith to Lithgow section of the Main Western Line, the forty members of the 46 Class were built by Metropolitan Vickers Electrical Co. Ltd. in Great Britan. Designed to NSWGR requirements, the class were the most powerful electric locomotives to be constructed (at the time). Delivery to NSW was three locomotives per month.

The class were not delivered in the standard "Indian Red" colour scheme, instead being delivered in a unique colour scheme described as a deep maroon red, with a single red stripe down the body of the unit. This red stripe split into three "wings" on either side of the headlight. The class would later be painted into Indian Red, "Reverse", Candy, Red Terror (4639 only) and Freightrail Blue.

When the first two members of the class entered service, the electrification beyond Penrith was not ready for use, so the 46 Class initially operated commuter trains between Penrith and Sydney. Once electrification opened to Valley Heights, and later on to Katoomba, 46 Class locomotives replaced steam on commuter passenger trains, as well as replacing the steam bankers based at Valley Heights.

When the electrification to Lithgow was completed in 1957, the 46 class took over the majority of Blue Mountains working, both passenger and freight traffic.

More 46 Class locomotives were delivered than were initially required for the Sydney to Lithgow running, so as electric interurban trains were delivered, and the electrification extended north from Hornsby to Gosford, the 46 Class were also deployed on the northern line, initially to banish the steam bank engines from Cowan Bank. Once electrification to Gosford was opened in 1958, all forty members of the class were in service.

During the early 1990s, the SRA suspended overhauls on the class, and by 1994 they were beginning to show the ravages of age. With National Rail not using electric traction, the SRA started withdrawls over 1994 and 1995.