what's the difference?

[CSX5202]

So after seeing that Union Pacific has SD40-2N's, I caught my myself wondering. What is the difference between the SD40-2N and a regular SD40-2?

[buzz456]

Well, apparently some got that designation on the sides, some got SD40-2, and some got SD40N, but they're all SD40-2's rebuilt at UP's shops in North Little Rock. But sadly it's pretty rare to see them in road service.

[bnsfsubdivision]

The 'N' part of the designation comes from UP's use of the NEXSYS control system from ZTR Control Systems, replacing the older Dash 2 component cards and control systems.

[Ericmopar]

Yes, technically they are not a Dash2 anymore, hence the "N" designation. We have some here in Vegas, they switch industrial and run up and down the Henderson branch line.
They still sound fantastic. I sometimes take a bike ride over to a local plastics plant and watch them switch on the steep grade out here. Lots of rumbling, and crashing sounds.

[CSX5202]

So, what are the differences between the dash 2 systems and the NEXSYS control system?

[bnsfsubdivision]

So, what are the differences between the dash 2 systems and the NEXSYS control system?

NEXSYS is a microprocessor system that not only incorporates a system to increases adhesion (allowing the engine to produce higher tractive effort) but it also simplifies the wiring on the locomotive between relays and contactors as the system controls digitally which combinations of relays and contactors to run.