I have a 1988 ford ranger 4x4 2.9L. Just had new heater core and electrical work. New tires and tie rods were installed last year last summer. Got it back from mechanic yesterday and it seems to be running fine, but I notice now that when I shift into 5th gear, it seems louder than usual. The RPM's seem fine and decrease as expected when going into 5th. However, I notice that if I downshift to 4th and maintain the same speed, the noise goes away. It returns when I shift back into high gear. The noise is hard to describe and I can't pinpoint it's origin, just that high gear is much louder than 4th, which is odd to me. Any suggestions. In fact, I notice that 4th gear is the quietist of all, lower gears are also noisy.