My 1976 Chevy Blazer K5, runs and drives excelent. But when I take it up into the mountains 4 wheeling, there is a problem. Any time that one or the other of the front tires goes up on a hill and there is any twist to the frame, I get this constant grinding noise. If I stop and put it in park, it still grinds and wont stop until the front tires on the same plane. What could this be?