BMW differential ratio identification (take off differential cover and you will see stamped code on a ring gear): https://e30.dev/files/images/diff_tables/diff_ratio_based_on_pinion_gear.jpg <table> <tr><td>typ 168mm</td><td>Small case</td></tr> <tr><td>H41</td><td>3.45</td></tr> <tr><td>H9</td><td>...