Can you use a Volvo 240 M46 overdrive on the M47 transmission?

No! The M47 is a 5 speed! The M46 a 4 speed with overdrive. It looks like

you might be able to do it but their parts are in no way interchangeable. The

M46 is a stronger transmission and generally outlast the rest of the car. The

m47 requires attention or you might have problems at say 200K.

Keep rolling!