I have a 97 ford ranger. 2 years ago my 4 wheel drive went out and I had it replaced, they replaced the 4 wheel drive with manual hubs. We have recieved so much snow that we have to engage the 4 wheel drive often. Last night we had locked the hubs in so we could lock into 4 wheel drive and we have a humming noise in the front end, but ONLY when the hubs are locked in and turning left or right did not make much difference. The humming noise is at slower speeds and seems to be less the faster we go and then when we turned the switch to lock into 4 wheel drive. It took a minute for them to engage and then as we were coming to a stop and it grinded. We aren't sure where we should start. Can you help us?