The Portland shops have a fairly limited manufacturing shopfloor compared to ILW’s actual locomotive works and in 1999 had a pretty large pile of new locomotives in the pipeline as well as an increasingly large pile of repairs that needed to be done to the oldest class Bs (and the nearly-nonagenarian class As), so when the PV&T’s operations department ordered another 4 class K locomotives the shops decided to order 4 sleds from ILW, then install the drivetrain down in Portland.

The class K4 is almost mechanically identical to the class K & K2 motors (it has a slightly higher horsepower and tractive effort, and of course it has a multisystem drivetrain so it can operate on D&H south’s 11kvac & 25kvac electrification) but it uses Portland’s radial trucks and the standard ILW streamlined design for their line of passenger locomotive (a design that was inspired by GE’s UM20 way back in 1953.)