I have a 2001 Buick Lesabre and it has a low rumble or grinding noise coming from the front. It doesn't do it at low speeds. It does it at 45 plus. It does it in both 3rd and 4th gears. It doesn't do it at deceleration so when it happens I can let off the gas pedal and it stops. The transmission shifts fine, no clunks or dips in power or anything.