Hey my 03 4wd element has a griding noise upon acceleration, such as a small hill or if u put some gas into your acceleration. Does anybody have any idea what it could be? once again a griding noise when accelerating, than if your flooring it up something, it will knock once or twice while still in 1st gear. also 1 more, my car when ideling at a stopline, while its still in drive, it will shakes pretty violently, and the tailpipe will do the same. but it be at the same stop light another time and not be shaking. any ideas?