I recently installed an 8.5" rear end in my Camaro. I put everything new in it except for the carrier. It was free and it looked good, so I used it. It is a factory style posi unit. I used Mobil One gear oil for the first couple hundred miles. During that time, my rear end made dull squeaking noises during tight turns. I put in the posi additive which made it a little better, but not much. The carrier seems to be very tight. Even in situations when one tire has alot more traction than the other, both tires will spin. A few days ago, I drained the Mobil One and put in Amsoil Series 2000 gear lube. The noise was still there right after I changed the oil, but it was gone the next day. I just got back from a 300 mile trip and the rear end is making the noise again. What do you think could be wrong? Should I put in a bottle or two of the posi additive or does the problem lie elsewhere?