Whining when in gear

Whining noise when driving. I jacked car up and once I put it in gear there is a whining coming from under. Cannot pinpoint if it's in the drive-train or gear box. With tires off ground I put it in gear I hear it and not when idling. When shifting to higher gears it gets louder and more prominent. I checked rear differential fluid and it is full only. Also last few months the shift knob has been popping of gear sometimes at take off. My car has 140,000 miles. My car has a manual transmission.