The Progress Rail PR43C is a 4,300 hp diesel locomotive built by Progress Rail Services. It is the result of a conversion of existing EMD SD50 and SD60 locomotives. This involves replacing the original EMD 645 or 710 prime mover with a pair of Caterpillar engines, a 3,600 hp C175 engine and a 700 hp C18 engine. The locomotive was jointly designed by Progress Rail and Norfolk Southern Railway. Development began in 2008.
The first three locomotives were manufactured at Progress Rail's Mayfield, Kentucky factory.
The process of converting an SD50 or SD60 to a PR43C alters the external appearance of the locomotive; the original radiator section is replaced with a larger one that is similar in appearance to that of an EMD SD70ACe.
The first two retained their standard cabs while the other 10 had Progress-designed wide cabs.
NS recently retired its entire fleet of PR43C's as they proved to be problematic, all were returned to Progress Rail in late 2017.