This beautiful 1982 300 SD has been making a knocking/banging sound that I think is coming from under the valve cover. The noise is not audible at low RPM or before the engine warms up completely. At higer RPM 1700+ the noise becomes increasingly loud and is directly rythmic with the speed of the engine. After probing the noise with a stick I think it may be from what I think is the oil pump (under the oil filter, or the transmission. The trans was probed at the bell housing also close to the oil pump (I think.) Is there anything that could make a loud noise such as this in these areas? Does this sound familure to anyone?
Thank you for any help!