1990 bmw 325i limited slip differential S373
 they pinion has 11 teeth and the ring has 41 but the gear ratio should be stamped on the pinion
 cf(3.73);
 ratsimp(cfdisrep(%));
              373
 (%o20)       ---
              100
 (%i21) ratsimp(cf([3, 1, 2, 1, 2, 2, 1]));
 (%o21) [3, 1, 2, 1, 2, 3]
 (%i22) ratsimp(cfdisrep(cf([3, 1, 2, 1, 2, 2, 1])));
              138
 (%o22)       ---
              37
 (%i23) ratsimp(cfdisrep(cf([3, 1, 2, 1, 2, 2])));
              97
 (%o23)       --
              26
 (%i24) ratsimp(cfdisrep(cf([3, 1, 2, 1, 2])));
              41
 (%o24)       --
              11
 (%i25) %o22,numer;
 (%o25) 3.72972972972973
 (%i26) %o24,numer;
 (%o26) 3.727272727272727
 (%i27) ratsimp(cfdisrep(cf([3, 1, 2, 1])));
         15
 (%o27)  --
         4
 (%i28) %,numer;
 (%o28) 3.75