I have a 1991 Ford Ranger 4x4 2.9 liter v6 5 speed manual trans. that the 4 wheel drive is not engaging. It is push button and has manual lockouts. When the push button is pushed it lights on 4x4 and 4x4 low and you can hear the motor engaging. I just had the wheel bearing replaced and am wondering if the manual hubs are not engaging. Should I just pull the manual hubs and see if they have too much grease on them and clean them? Any help would be appreciated.