When you say you "tried' the NSBU switch, what do you mean? Replaced it? Who's instructions did you follow? Are you sure you kept the shaft lined up correctly?bubba;1583275; said:hi guys! i have a 05gmc 3500 dually i have reverse only no forward gears at all-trans fluid all ok! prindle flashes in forward gears and message is range selection inhibited ! no codes!! tried nsub switch no different! HELP PLEASE!!!