I have an 04' ES (all wheel drive) with 206000 kms I have replaced the front brakes (rotors, pads), both front wheel bearings and sway bar links. There is still a significant "gear" like noise that is present while driving. Does not change during turns or acceleration or deceleration/acceleration although gets a bit louder the faster I go. The transaxle, transfer case and rear diff fluids were all changed @ 160,000 kms. When I changed front bearings the 1/2 shafts and cv joints seemed tight with no tears in the boots. Struts are good with no leaks. Could this be in the hanger bearing to the rear axle? Food for thought.

 

Could be that bearing but the pitch should increase with road speed as it is proportional to road/diff speed.

 

Yeah it is definitely metallic as I can feel it a bit through the floorboards. Maybe the U joints in the driveshaft. Tires are Michelin LTX M/S II and are very quiet I will play underneath this week (when the rain stops) and post the results. Otherwise a robust vehicle.