2004 a6 3.0l quattro tiptronic. Been hearing a thud or bang under drivers seat when slaming on brakes or reversing while turning the wheel. suspecting motor mounts I changed pasengerside and front mounts and no difference. and as of late car feels out of control going over bumps. Have purchased the transmishion mount, has anyone replaces this mount before. I have also had a nightmare with vibration issues with new wheels and tires.

Need more information than that. Could be a loose shock. When do you hear it most? When do you hear it least? Does it sound like a rattle or deeper thud? Could even be the exhaust hanging loose. You say interior but I'm guessing right rear. Is it braking ok?

Google it - Check this LINK. If your horn or other steering wheel controls do not work, it's likely the clockspring - the device that transmits the inputs from the steering wheel into the wiring harness under the dash. Pray it's not, otherwise your Audi tech will be buying himself a new S4.

Td

Make sure the parking break is off, has the cable seized? If the vehicle has been parked with the parking break on for a long time, the brake shoes can stick to the drum!!!!(yes they can hold that tight). If this is what caused the problem, you can try banging the wheel, while trying to reverse the vehicle (only if they are steel wheels), If not take the wheel off and work your way round the drum banging as you go. Other possible cause is a brake linning or linkage come off and jammed the drum, if thats the case good luck, you will possibly have to result to cutting gear and damage

wew

could be a bad brake caliper, try riding brake and hit a bump did it quit? loose exhaust system, boken strut or shock, broken sway bar stabilizer bolts

Possible front road spring binding due to upper tower bearing seized or stiff.

Maybe spring seat perch breaking up. Weld coming apart....dangerous condition. Many MBZ cars affected.

Have this checked out immediately due to possible safety hazard.

u joints rear end front driver

i would check that the emergency brake in the rear brakes havent fallen apart. i believe on this model there are shoes inside the hat of the rotor for the ebrake.

Get a spray can of Brake disc quiet from Advanced Auto and coat the disc let set for one hour then take out and drive at the same time rotate your tires if the noise comes from a different wheel after rotating then it is your tire if it continues from your drivers side then your caliper needs to be removed and readjusted because the piston is not fully depressing.

The problem could be caused by a wheel bearing squeeling or the cv joint squeeling.