Ray - I looked this up in the Bubeck/Garrigues book and 8458 is a GP-9, offered in 1984, with Southern the only production road name. The brief history write-up in the B/G book says that Lionel started using can motors in AF locos in 1982, so its likely that's what the 8458 has. I think your suggestion about giving the gearing, etc. a good cleaning and relubing is a good place to start. Luckily (well, maybe) the can motor eliminates having to fool around with an old open frame motor (e.g., brushes and commutators and ...). Did locos of this vintage still have the old rotating drum reversing units? That could also account for reverse not working as well - dirty contact surfaces on the drum and fingers, etc.