I am a new owner of a pre-owned 2001 F-150 XLT 4x2 S-Crew and haven't the foggiest idea what gear ratio is in the truck. How can I tell?

 

Check your door post sticker for "Axle Code."

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)

 

Thanks for the information.