Trying to figure out that code rear diff I need to finish my swap. I know I need a 4.11:1 rear, but the dealerships have been useless to figure out what code I need. I have already checked one car I know, and it was code "EUU". The confusing part is the other cars equipped with the EUU code rear diff were geared for a 3.73:1. Did Audi put different gearsets in the same code diffs? The code is posted on the build sheet in the spare tire well on the passenger side. It is also located in the first page of the warranty booklet, but that is only useful if it is the original one to your car. If all else fails, it is stamped into the bottom of the rear diff. Below is my sheet for reference. Thanks in advance!