2002 buick century "slight thud and moaning" sound

[Chevymike01]

Hello all,
I have a 2002 Century with the 3.1 V-6. It has 65,000 miles and runs great. I've had it for a year now and since I've had it, the car has made like a "thud" sound and feeling only at 15-20 mph. Anything over 20mph or below 15mph, it goes away, but always in the 15-20 mph range it's there regardless if you're speeding up or slowing down to that speed. It seems to be conditional on a rotational basis. I have since put on 2 new front tires thinking that the tire may have had a bubble in it, but to no avail. I've lived with this condition for the past year since it was not affecting anything. Now, I'm hearing a "slight moaning" sound (like if you held a piece of paper next to the spokes on a bicycle wheel and spun the wheel fast) from the front passenger side of the car. I jacked it up and took both wheels of the front and had my wife sit in the car and bring the speed up and the "slight moaning" noise was still present. My thoughts are that it could either be a transmission issue, a bad CV joint, or bad wheel bearing. The transmission has been shifting and doing fine. I did a tranny service (dropped the pan and replaced the filter and fluids as well as put a thing of Lucas in for good measures) on the car at 50K. Can someone please help me out with what they think the issue is? Thank you very much.

[ricebike]

wheel bearing? ball joint? tie rod? another suspension component?

can't be a CV joint; it clicks on a turn if it's bad...

cant really do this over the internet... some shops would do an under-car /suspension component inspection before they put it on the rack for a wheel alignment...