Superduty Axle Codes

F350 duallys

61 - open - 3.73
62 - open - 4.10
63 - open - 4.30
F1 - Limited slip - 3.73
F2 - Limited slip - 4.10
F3 - Limited slip - 4.30

F350 SRW

41 - open - 3.73
42 - open - 4.10
43 - open - 4.30
D1 - L/S - 3.73
D2 - L/S - 4.10
D3 - L/S - 4.30

F250 & Excursion

31 - open - 3.73
32 - open - 4.10
33 - open -4.30
C1 - L/S - 3.73
C2 - L/S - 4.10
C3 - L/S - 4.30

My early '99 has C1 listed on the door plate.