Can I change my derailleur without changing my shifter? I have Shimano V-Brake 8-speed shifters on my bike. These have the brakes and the shifter in one component. I'd like to change my derailleur can I put in a newer 8 speed Shimano derailleur that will still work with the old shifters? It'd save me from buying new shifters AND brake levers.
Yes.
All Shimano MTB groupsets up to 9 speed all used the same derailleur actuation ratio (how far the cage moves for a given cable pull), so all 8 speed MTB shifters are compatible with all 8 speed MTB derailleurs.