I just picked up a posi unit for my 12 bolt. I'm keeping the same gears since they are 3.73's. How hard is this? I build all my own motors but am not too good with diff's. I'm guessing this shouldn't be too hard since I'm not changing the pinion depth. I have all kinds of shims and a dial indicator with a magnetic base. Any helpful links out there?? I'm told it's an issue of backlash. Should a check that before I pull and then set it back to that?? Any help would be great!!!! Thanks!!!