Hopefully someone here knows a little about mustang rearends. I have a 2011 mustang gt. Just had the Ford dealer replace my old ring and pinion bc it was whining. They were 373s and I went back with the same. Now, I hear a knock noise only when I have my foot on accelerator while in gear. For example, if I'm going 50mgh in 6th gear, I can hear a knock. If I'm at 50mph in 5th, I don't hear it. I may not hear it bc my exhaust is so loud. But the main thing is I only hear it while in gear.