Steam locomotives have scheduled maintenances every 31 days, with more in depth 92 day and annual inspections.
Older diesel locomotives have 92 day maintenance, with a 184 day that's more intensive and then an annual that's even more intensive.
Locomotives with computer controlled air brakes only have the 184 day and 368 day maintenances.
You've gone from 12 dedicated maintenances a year to 2 from steam to diesel.
Class overhauls are once in maybe 25 years or so. We still have a good handful of Santa Fe units that haven't been repainted because they haven't been through overhaul at BNSF.
This also doesn't even consider the time of doing the work on the locomotives. Two guys can change all the traction motors out on a diesel locomotive in an 8 hour shift. Two guys can change 3-4 power assemblies (cylinder head, cylinder, piston, connecting rods) in an 8 hour shift. There are ready made parts for most everything, and nowadays sensors all over the locomotives to tell you what's broken.
I love steam. I don't particularly care for the diesels that I deal with on a daily basis now but it's obvious as to why the change was made.
Mark Huber
Hyce on YouTube