My bike rack is a Yakima SingleSpeed. I have a 1-1/4" Class I receiver hitch on my Ford Focus, because that's all I can get for it, so I appreciate the racks that work with it.
It has an internal clamping mechanism that takes out the play in the hitch to keep the rack from swinging and rattling around. If that's not super tight, it will eventually work itself a little loose, and that's when it creaks. Going back there, positioning the rack square in the hitch, and torquing it down good takes the creak back out.
The one thing I don't like about mine is that if I forget to put the rear wheel strap on (which I have done twice), the rear of the bike will bounce out and then drag on the highway and rather instantly bend up the rim (which it has done twice). It's obviously my fault when that happens, but somehow the design of the thing lends itself to me forgetting.