What happens if you slightly drag the brakes when the noise is happening? Does the noise go away or change at all? Does going over bumps change the sound? Check brakes, rotors, pads, pad backers, struts, springs, and related strut parts
Something different: You changed the transmission fluid, do not forget about the read end, transfer case, and the AWD coupler fluids too. You check the drive shaft to the rear end with the hanger bearings and joints? With 177,000 miles there is going to be a lot of stuff worn and close to being worn out if the car was not properly maintained through out it life up to this point.