Hi, I've got a 1989 K1500 Sportside with only 35 000 miles on it. It has started this scratching sound when accelerating, like metal against metal. If I slighly ease the pressure on the gas pedal, it stops. If I really step on it, the sound stops. But when sort of right in the middle and then slightly accelerate, then it starts. Anyone having had similar experiences? Engine and transmission work perfectly.