I have a 98 cobra with 3.73 gears. This past spring the gears started whining and have been getting progressively louder, especially at 55, in all gears, it seems to be more speed related than anything to do with what gear it is in. In all gears the whine is the same. Its not the tires, they are not that old and have plenty of tread. They are Riken Raptors, 275/40-17's. I can hear it at speeds of 5mph on up. The rear has already been reshimmed by a good mechanic friend of mine. It was 6 months later that the whining started. It also doesnt change tone when turning left or right, braking or hard accelerating, or idling at neutral, so its not the fuel pump. Its just there when moving forward and loudest at 55mph. I changed the fluid when it was reshimmed, using the 80-90w (i think..) motorcraft gear oil, and half a quart of heavy duty lucas oil. Im about to change the fluid again to see if that helps any. Gonna use 75-140w mobile one syntec with a whole quart of the lucas this time. Any suggestions as to what this problem is, could be, stems from, how to fix, etc?