I have a BX 23 bought new 2-1/2 years ago, It currently has 38.4 hours....This weekend I needed to dig a 10ft. trench with the backhoe on a side slope...kinda dangerous I know... As I was positioning the tractor with it listing to the left with the front slightly dipping forward, I heard what sounded a distinctive lower engine knock....The engine RPM was low as I was very cautious in positioning the tractor...The knock went away when I raised the RPM...I dug the trench... When I lowered the RPM again to get the tractor on a level plain the knock came back intermittently and driving it back to the tractor shed, all was fine, like nothing happened....The oil was at the full mark? I'm concerned, as now its out of warranty....Any thoughts?