Hi. I have a 2001 Saturn SL1. 109k miles. 4 brand new tires (last week). For the past 6months, something in front left of car makes a "grrrrr" noise which only starts to be noticeable when going faster than 30mph, and increases in volume, and pitch, with speed. I don't think it's the engine or transmission, because I was on highway and bumped into neutral and could rev the engine but the grrr sound was still constant and only changes pitch with speed. Also changes pitch momentarily if I hit a dip in the road. Even the 4 new tires I installed make no difference in the grrr. Wheels and stearing wheel doesn't really shake or anything abnormal. I've read about wheel bearings potentially being such a cause. Or maybe, if pitch changes when I hit a dip, could it be an engine mount problem? Any ideas? Thanks Theodore.