Id'ing them:
Differentiating them from a borg-warner (KE70 / AE71 diff) and a S-series (ADM AE86, AE71 Panel van)
easiest way to tell:
Borg warner: Removable inspection plate (on the rear of the diff housing)
S-Series: Removable 'nose' with 8 bolts holding it in (on the front of the diff housing)
T-Series: Removable 'nose' with 10 bolts holding it in (on the front of the diff housing)
If you're still skeptical, then you can pull out the 'nose' of the diff and measure the crownwheel sizes
S-Series: 6.38"
T-Series: 6.7"
If you want to know what ratio it is, then this little bit will help (copied from old toymods)
first digit: ring gear diameter
A 138mm
B 145mm
C 6.25"
D 6.62"
E 7.1"
F 7.5"
G 8"
H 9"
J 9.25"
K 9.5"
L 10.5"
M 12.5"
N 13.5"
P 14"
Q 12"
R 162mm
S 6.38"
T 6.7"
U 6"
V 10.6"
W 15.5"
X 142mm
Y 158mm
Z 202mm
- no ring gear = FWD
Second, third digits: gear ratio
01 3.30
02 3.36
03 3.545
04 3.556
05 3.70
06 3.889
07 3.90
08 4.111
09 4.222
10 4.375
11 4.444
12 4.625
13 4.79
14 4.875
15 5.125
16 5.286
17 5.60
18 5.714
19 5.833
20 6.167
21 6.667
22 6.78
23 6.833
24 7.64
25 4.556
26 5.571
27 3.364
28 4.30
29 4.10
30 3.727
31 3.909
32 6.591 or 4.807
33 7.503 or 5.583
34 6.781 or 4.786
35 7.636 or 5.60
36 4.778
37 3.583
38 3.417
39 3.154
40 5.375
41 3.308
42 6.500
43 3.550
44 3.214
45 3.533
46 2.928
47 3.944
48 3.356
49 3.729
50 3.400
51 3.736
52 3.722
53 3.250
54 3.941
55 3.333
56 2.821
57 4.058
58 3.238
59 3.234
60 3.519
61 2.724
62 2.892
63 2.655
64 4.312
65 3.837
66 3.071
67 3.526
68 3.095
69 4.176
70 5.857
71 2.962
72 3.949
73 4.285
Fourth digit: no of pinions, ltd slip-yes/no
Code pinions ls
2 2 no
3 2 yes
4 4 no
5 4 yes
This should be on the firewall of the donor vehicle, possibly on the diff (dunno)
Width of the T Series housing from different models:
TA22 (73 onwards), RA23, RA28 - 1365mm (mounts will not line up to xE7x / AE86)
RA40, RA60 - 1410mm (mounts will not line up to xE7x / AE86)
JDM AE86, TE72 - 1410mm (mounts WILL line up to xE7x / AE86)
Those are the main ones at least.
Oh, JDM Zenki T-series have the same axle thickness as ADM T-series diffs (TE72 ones)
JDM Kouki T-Series have axles which are approx 1- 1.5mm thicker.
Javal.