I locked my front diff on my 86 5000CSTQ, and when I went to take it out of lock, it made a grinding noise followed by a complete lack of forward motion. I can drive the car with the diff locked but it won't move with the differential unlocked. Unfortunatly Bently is no help, anybody have any ideas? Bill Erskine 86 5000CSTQ 94 100S 71 Chevelle 454SS