My car is in the subject line. When driving down the road I hear a "ch ch ch ch ch" noise at 2200RPM ONLY. It does it in every gear but does not do it below 2200rpm or above it either. I had my dad drive it and I rode in the bed it is ver noticeable between the cab and the bed and sounds like its towards the rear. It does not do it while idling or in neutral. What could this be? Please help!