Just bought a 1992 Ext cab Cummins Turbo Diesel - Great shape - 150k miles. Here's the problem. I get a rumbling sound when I go around a corner or curve (feels like grinding - kinda). Just did new rear brakes - will check the fronts tomorrow. Feels like grinding, but doesn't sound like brakes. I assume it is happening at higher speeds, but I only notice it at lower speeds. It also happens if I coast around a corner or curve in neutral. Could this kind of thing be a transmission or drive shaft problem? The auto-trans shifts smoothly through all gears. Any ideas?????