look at the tag on the rear diff. it should be a little metal tag that is bolted down by one of the cover bolts. it should tell you gear ratio and if its limited slip. if its limited slip youll need to add friction modifier. but this might also help......youll find the label in that image inside your drivers door jamb area.....either on the body or on the door.
Vehicle Certification (VC) Label
Item Description
1 Exterior Paint Code
2 Region Code
3 Domestic Special Order Code
4 Wheel Base Code
5 Brake Code
6 Interior Trim Code
7 Tape/Paint Pinstripe Code
8 Radio Code
9 Axle Code
10 Transmission Code
11 Spring Code
Axle Codes
The following lists the gear ratios on rear axles.
19 — 3.55 non-limited slip (Econoline, F-150)
18 — 3.08 non-limited slip (F-150)
17 — 3.31 non-limited slip (Econoline)
H9 — 3.55 limited slip (F-150, F-250)
B6 — 3.73 limited slip (F-150, F-250)
24 — 3.73 (Econoline)
32 — 4.10 (Econoline)
35 — 4.09 (Econoline)
34 — 3.73 (Econoline)
39 — 3.55 (Econoline)
52 — 4.10 (Econoline)
56 — 4.10 (Econoline)
81 — 4.63 (Econoline)
27 — 3.31 non-limited slip (F-250)
26 — 3.73 non-limited slip (F-250)
41 — 3.27 non-limited slip (Explorer/Mountaineer)
45 — 3.55 non-limited slip (Explorer/Mountaineer)
46 — 3.73 non-limited slip (Explorer/Mountaineer)
42 — 4.10 non-limited slip (Explorer/Mountaineer)
D1 — 3.27 limited slip (Explorer/Mountaineer)
D4 — 3.73 limited slip (Explorer/Mountaineer)
D2 — 4.10 limited slip (Explorer/Mountaineer)
84 — 3.45 non-limited slip (Ranger)
86 — 3.73 non-limited slip (Ranger)
87 — 4.10 non-limited slip (Ranger)
89 — 4.56 non-limited slip (Ranger)
F6 — 3.73 limited slip (Ranger)
F7 — 4.10 limited slip (Ranger)
92 — 3.08 non-limited slip (Ranger)
R5 — 3.55 limited slip (Ranger)
91 — 3.27 non-limited slip (Ranger)
96 — 3.73 non-limited slip (Ranger)
R6 — 3.73 limited slip (Ranger)
