Hello all,
I just put a camaro 3.45 diff in my g8 and my tuner put in the tie info and the 3.45 gearing and my speedometer was way off. We went back and forth with tire size gearing and could not figure it out. So we started to dramatically change the gearing in the tune and started to get somewhere by first putting 3.73 and then got it perfect with a final gearing of 3.90. So my question is why does the gearing have to be set at 3.90? Did I get a 3.90 diff because I didn't think those fit? We were both confused by this and any info about this would be great. Thank you all in advance.