Centercaps would quit making noise at some particular speed as the speed of the vehicle increased due to road noise increase & inertia, the rotational speed of the wheel(s) would keep the caps from hitting the side, virtually the same as when a u-joint goes. For the same reason, you only notice a u-joint clicking when you are changing front to rear direction, or when going around a corner. When the vehicle goes faster, road noise picks up as does the inertia and will now only allow the bad u-joint to travel a little, or none at all. It will self-center as speed due to the inertia of the u-joint. And fwiw, I have on more than one occasion had a u-joint go out but it sounded like it came from the front end, so i chased a ghost for a while till I lookked at the u-joint. Put the vehicle in park and rock the vehicle from front to rear, or alternate putting the car into drive and then reverse very slowly, listen for the infamous click-click. U-joint click is reasonably audible, though, almost a clack or light clunk.
HTH