Don't forget Montana rail and BN who got the newest and last ordered units from the grand and beautiful GN. Really really heartbreaking to see them finally go in the early 2010s
This is definitely a turbocharged locomotive, the sound you are hearing might be the rear geartrain. These would be positioned closest to the back of the cab. If the gears are worn or certain things are not installed properly causing excessive backlash in the geartrain, they will become louder and sound more like a roots blower powered unit. This might be the case here. If you listen closely, you can still hear the whistle of the turbo.
@@trainandtruckmodeler786 Cool. But, reportedly, didn't most engineers dislike the GE Dash 7's and prefer the EMD's? I remember reading of one engineer's disdain for the toilets in the Dash 7's.
It's just the acoustics of the car body combined with reverberation in the cab - changes the frequency of the sound. Also worth noting that functionally a 710, 645 and 567 are all pretty much the same basic engine with continually improving components and features, so minor differences in perspective or acoustics can make one sound like another sometimes. You'd be surprised how many videos I've seen an SD70ACE go by and thought to myself "huh that sounds like an SD45" Could also be the worn turbo as Ricky mentioned but I've seen cab footage from the 80s and 90s where 645s still sounded like 567s, so I think its just as simple as you can't hear the turbo as well inside the cab, especially with a metal carbody shrouding the engine.
@@alecmesa7563 I listened to it again and yes, it has a turbo. It's all in the acoustics and how the microphone picks up the sound. I made some recordings in the cab when I was running F59s and MP40s and they sound the same way.
