So, it is coming off of 2002 E39 M5 with 20K miles on the diff. The info from the dinan site is for the M5 3.46 diff. They don't make a 3.45 diff for the 540i manual. Dinan only makes a 3.15 diff. for the 540i manual and it costs $7000. I think that the M5 stock diff. is different than the the 540i stock diff, hence the huge price difference for a 540i Dinan diff. and a M5 Dinan Diff.