NS SD40 prime mover

[David Collins]

A few months back I was at the parking lot of international wholesale next to NS' Oakwood Yard onlooking trains, and there were two NS SD40's working the west end of the yard, 6143 and 1629.

I found that 6143 and 1629's prime movers sounded different compared to each other. Instead of sounding like a 645 prime mover, 1629's almost sounded like some sort of 710 prime mover or a late model 645, and 6143 just sounded different, and I couldn't put my finger on it. Do the yard units such as 1629/6143 use a different block, or am I just hearing things and going mentally crazy?

[Thatmichrailfan]

Actually, You might be onto something. Looking at RRpictures online shows me this.. https://www.rrpicturearchives.net/showP ... id=5908873 (I don't know how to embed photos hahah)

[SD80MAC]

All SD40s use the 645E3 diesel engine. During the course of SD40 and SD40-2 production, there were different exhaust silencers fitted to units over that nearly 20 year period, which does affect how they sound. Some units have also had their power assemblies upgraded with 645F (like the SD50 and GP50) components. CSX's SD40-3 and GP40-3 units are good examples of this. A 645F sounds a lot more like a 710 than a 645E3.

There are some SD40s that have been rebuilt with 8 and 12 cylinder 710 engines, but they are no longer SD40s.

[BnOEngr]

EMD also changed vendors on the turbos, which accounts for a sound change as well.