Well, I searched but was not able to find it on this site. So in case someone else searches for them, I thought I'd post this info here:
Axle Codes
L - Limited Slip Differential
C - Conventional Differential
Code ... Ratio
41 ...... 3.27C
42 ...... 4.10C
43 ...... 3.08C
45 ...... 3.55C
46 ...... 3.73C
D1 ...... 3.27L
D2 ...... 4.10L
D4 ...... 3.73L
D5 ...... 3.55L
Transmission Codes
Code .................. Model
D (1997-2005) ..... A5LDE / 5R44/55E
D (1992-1996)...... M5OD-R1
J ....................... M5OD-R1
J (2002-2003)...... R1HD / M5OD-R4
M (2000-2001)..... Mazda M5D4
M (1997-1999) .... M5OD-R2
M (1992-1996) .... M5OD-R1
R (2002) ............. 5R55W
T (1992-1995) ..... A4LD
T (1996-2001) ...... 4R55E
U ....................... 4R70W
V ....................... 5R55S
X ....................... 6R60