My lumina has 125,000 miles on it and when I'm accelerating from a stop my car has a rumble to it. Its optimum sound level is when im at 15 mph on a smooth blacktop road and as I increase speed the sound fades but I can still hear it. I thought it was the driver side rear wheel bearing so I changed the assembly and it didn't correct the problem. Any ideas?

Run your hand across the tread face of the front tires all the way around. A "feathered" tire on a FWD car will do this....sounds/feels almost like the brakes are grinding when it's real bad...

If that's it, you need the alignment/struts checked.

The nature of the sound as you describe it sounds very much like this problem....

alright that is something i haven't even thought of so thanks I'll check that out and I'll let you know.