Wierd engine noises

Check your trans oil level. My 05 will make the "whirling" sound when the oil is low (best way I know to describe it) like my 99 Cr did. I don't use the oil level check screw. I put in about 50cc more than the manual state (700cc I think) and all is good. The motor has about 25 cross country races on it since Nov 05 and I'm guessing about 300 hours on it. I have replaced the piston, intake valves, valve springs and seals and the associated gaskets. The bottom end is stock. I change the oil every 3 practice rides or every race weekend. I use Silkolene Race 4T 10W-40 (full synthetic in both the engine and trans, it is clutch safe). All has been good so far. I did notice some small aluminum shavings in the oil filter last time I changed the engine oil. I'm thinking it is oil pump related as it is mounted inbetween the cases. I plan on a rebiuld this winter (crank, piston, valves and anything else I find) and hope to get 3 more years from it.