I have a 2005 with a 11.5 American Axle 4x2 3.73 gear. I need a replacement rear as the ring and pinion in mine is toast. Well it seems trying to find one is harder than I thought. Why is a 4x4 11.5 different than a 4x2? 4x4 rears seem easy to find. But What would be different between the two? I have a 07 CTD 4x4 and they look the same? Thanks in advance, I'm stuck with the rear end out of my 2005 now and can't find a replacement.-----------Roy