I have a M4900 that is leaking oil from the oil seal located on the differential lock shaft. Want to replace it but can't seem to remove the lock lever spring pin. Anyone have an idea how to get this out? It is a hollow aluminum pin that is seated flush to the lower and upper side of the lock lever. Having a difficult time finding anything of correct diameter to pound it out with a hammer. Everything I've tried from punches and screw drivers do not budge it.