Some cars, no matter how you try, just seem to be noisy. First in the league are SCX cars followed by a host of older cars of various makes. First thing to check is the condition of the crownwheel and pinion. If that's OK then it's probably the second fixings in the body.
These are bits that go into the body to give it more detail like drivers trays, lights, fire extinguishers, drivers and a host of other bits. The simplest solution is to remove the body from the chassis, squirt a small drop of superglue onto a piece of waste plastic or metal and using the point of a modeller's knife, apply a drop of glue to all the heat welds under the car.
The bits that hold the lights in, the drivers bum, drivers tray, edges etc.
Finally, using a modeller's fine flat file, take off all the rough edges and high spots from the chassis and body where they come together. Do this until the chassis slips freely in and out of the body.
All going well, with body screws backed off slightly, even an SCX Audi R8 will glide silently around the track!