I had the impression (riding behind a Trainmaster) that dice were rolled at every station stop to determine how far to open the throttle when leaving - they took off like a bat sometimes.

So how did the GP9's work? At that time they certainly had transition, but they also apparently were able to keep up more or less for acceleration.

Then there were the F40s. Amtrak and original Caltrain versions had the constant-speed engine (for HEP) - so how were they controlled for traction power? Presumably by then transition was no longer required?

I have to admit that despite growing up in SF I never saw SDP45s in commute service. TMs and GP9s, yes (rode behind a few), and even once (late 1950s, I think) something steam, and later early Caltrain, but I guess other things went on while I was out of town in college and early jobs. Oh well.