Pontiac Repair: 1996 Pontiac Grande Am wheel noise, routine oil changes, market hubs

Question
Hi, my car has been making a thumping noise in the right wheel area for some time.  Each time I take it to a garage they change something, but the thumping noise is still there.  This noise starts when the car is warm, and stops when I depress the breaks a little, not even to a stop.  One man told me it is in the back of the hub where there is a large bolt that has some kind of an inner washer/housing inside the hub. He said this housing is worn and is allowing the nut to move around and the fact that the noise stops when I depress the breaks is proof.  He allowed me to go under the car and I can see the back of the break pads close to where this bolt is.  This makes sense to me and I want that part repaired, but the mechanic pretends I am stupid and wants to change all sorts of expensive parts.  My tire is in no danger of falling off.  This is something inside the hub/back side of the wheel.
Please tell me what this bolt and it's internal anchor is called so I know when the mechanic is telling me the truth or going on an expensive treasure hunt.

Note: I have had the front end checked during routine oil changes and tire changes and am assured that all of the external mechanisms are sound and nothing is going to fall off.  I do want to get rid of the thumping and save my vehicle for as long as I can.

Please help me.

Answer
Hi Shirley:

Excellent discription of your problem but It really doesn't help me too much the explanation you got doesn't make much scence. I would look at the wheel bearing/hub assembly it's self If there is any kind of play in the bearing it needs to be replaced It will not get any better. If you had the hub replaced before if it's not a factory part I have seen the after market hubs make all kinds of gooy noises and clicking thumping noises. Nothing should be rubbing touching anything other than the brake pads on the rotor. You could have a rust build up or ridge on the rotor that when the car leans one way or the other that ridge of rust is rubbing on the pads or the caliper it's self. I'm thinking it's something to do more with the brakes rubbing due to thew fact it does it once it's warmed up. But without seeing it or hearing it I can't really give you a good clear cut answer sorry :( Good luck ... :)