I think that this is a mode of torsional vibration of the crankshaft. >Uh, right. I was taught that the "hammering" feeling of lugging an engine >is caused by the pistons suddenly trying to go a lot faster than the >crankshaft. _________________________________________________________________ Add photos to your e-mail with MSN 8. Get 2 months FREE*. http://join.msn.com/?page=features/featuredemail