What rear end gears do I have? 4:10?

[SharkDiver]

hey all,
Im tring to figure out if I have 4:10 or 3:73 or whatever in my new used F250 xlt FX4. It has the towing package if that matters. The tag on the rear end cover say B445.
Maybe some of you could help me this way..I have the 5speed auto and when Im driving 55mph my rpms are at 1.5X on the tach.
Ive been looking for ways to tell and I know I could jack up the car and turn the axle and count the wheel spins but thought there may be a easier way.

Thanks,Shark

[dazdillenger]

sounds like you have 373's from the rpm given, but check your door tag-it should list a code under AXLE

[Raul@Stealth Automotive]

most F250's came with 3.73 gears

[SharkDiver]

ok,Ill check the door for that code. I thought I read that that code will not tell what gear you have tho... I could have read that wrong tho. 3.73 is what i was hoping for tho. Im looking to get the best mpg possible since I drive 75 miles everyday.