1998 Mazda b4000 6 cyl Four Wheel Drive Automatic 112000 miles
We replaced the rear end because a mechanic looked at the truck and said the gears where worn. After we've fixed it, we took it for a test drive, and everythings was fine until we hit 70 mph, just like before, it started humming very loud like the axle was trying to stab. Once we engaged it in 4 wheel drive hi or lo, the noise goes away, and the vehicle opperation is normal. Can you help?