1996 Chevy silverado 4x4 w/manual trans w/160 K miles. Towed 5000 lb boat/trailer 2 hours. Smelled burnt oil. Trailer has surge brakes. Checked rear end oil. rear end got real hot, oil burnt. Oil level OK, no metal chunks or particles. Changed oil 30 K miles ago. Ran truck home without boat/trailer with a slight whine from rear end. Question - did I burn up the bearings? Any experience with surge brakes - possible cause? I hate to rebuild it and have it happen again. Any help would be appreciated. Stock Chevy parts, don't know what gear ratio rear end is. Thx.