The one that came out was a 12" and probably a stock unit. I wanted to put a new one in since going through the transmission. I know the old one when I put it in gear if I did not hold the brake hard the tire would chirp on the garage floor. There's probably nothing wrong with it. I'm going to take your advice and see if I can get an 11 inch. They will probably have to order it since they did not have any 27 spline units in stock.