For about a month and a half I have noticed a tapping noise from underneath my truck. I only hear it when I am on the gas, and in gear. There is no noise when it is not in gear. I have an automatic transmisson, and I checked the fluid level and that is fine. I also checked my oil level and I was about a quart and a half low (last oil change about 2800 miles ago). Some days the noise is more noticeable than others. I have no slipping with the transmission and I don't feel the tapping in the pedals. The noise is normally only when I get the RPM's up higher. Does anyone know what could be going on? Thanks

 

What engine?

Cat. Conv. possibly.. Try giving them a solid 'bump' and see if you can hear the core rattle.. If the core breaks loose, it tends to rattle more with a higher volume of exhaust passing through the pipe/s, or on a throttle snap...