Jim Fitzgerald Wrote:
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> As someone who knows not one diesel from another,
> what was the difference between an SD-39 and an
> SD-40?


As Tom said, 700 HP.

The SD40 has a V16 turbocharged 645 engine, 3000 HP.
The SD39 has a V12 turbocharged 645 engine, 2300 HP.
The SD38 has a V16 non-turbo 645 engine, 2000 HP.

Spotting features from the outside, the SD40 has 3 radiator fans, the SD38 and SD39 two radiator fans.

The SD38 has 2 exhaust stacks and sounds different than the SD39 or SD40, which have one stack and turbocharger whine as the main component of their sound, the SD38 has EMD non-turbo "chant" as its noise.

Note that UP has a few units it runs in Roseville hump yard service that are SD40s that have had their turbocharged engines replaced with non-turbo V16 645s, so they look like SD40s, but sound like SD38s and have 2000HP.

Some non-turbo UP units have 4 stacks. I think this is an old MoPac modification that UP continues to use, as I've seen old pictures of MoPac Geeps with 4 stacks.