I bought a rebuilt differential for my 77 vette from a reputable Corvette parts distributor. The catalog said nothing about possible road noise but when the differential arrived there was a flyer stating "differential not guaranteed against road noise". The Chevrolet dealership doing my work already had the rear end tore down awaiting the rebuilt differential and also needed the lift my Vette was on for other work. In other words I had no choice but to go ahead and install the differential. Well, sure enough it had plenty of road noise and I had to live with it until I found and could afford a reputable rear end specialist to set it up right, so to make a long story short, if you are going to buy a rebuilt differential be darn sure and ask about road noise.