In 4WD while coasting downhill or with any let off of the throttle there is a growl or humming noise from the TC that was not there last winter. It does not make any noise in 2wd. I did find that it was 1-2 pints low on oil, filled up with +4 which yielded no change. Last winter I replaced all the u-joints, wheel bearings, ball joints and changed the oil in the TC. Last night I jacked it up and checked everything and can find nothing wrong in the front end. Any ideas would be appreciated. Thanks.