2002 Chevy Silverado transmission Problem

Check the transmission fluid. Make sure it's full and not burnt. You should change it and look for any excessive friction plate material in the fluid. Also when changing the fluid replace the filter, it could be blocked up.
Inside your transmission there are electrical solonoid valves that regulate the flow of trans. Fluid. The trans fluid is under extremly high pressure so it can press pistons, that press clutch plates, that make your truck move. If the fluid is low enough air bubbles from in the fluid which makes a whinning sound. Also if the fluid is low then there is a leak somewhere. With only 46,000 miles this is rare but I guess it could happen. Keep me posted
I also dought the problem is electrical, is there something that leads you in this direction?