How do you figure the axle ratio?  I'm looking in my owners manual for towing info and have looked at the tag on the drivers side door frame.  Nothing stnads out.  I have a f-150, 4x4, w/ tow and off road package.

Thanks.

Crawl under there and look on the rear housing, often it is on a tag there.  Also, call a dealer, give them the VIN #, and see if they get it for you.

You can also do it mechanically by jacking the vehicle and comparing the rotation of the drive shaft to the rotation of the tire. It's more difficult to do with a posi unit. The tag is the easiest way,

Gard

Check the above like everyone said, the sticker on the door will have a code then call your local Ford dealer and he can tell you for sure.

Depending on year model, 96 and older F-150's that are 4x4 with the 5.8L engine and automatic transmission is going to be a 3.55 ratio, if it has a 5.0 engine and automatic it could have 3.08's.  97 and newer 4x4's most had the 3.55 with a 4.6 or 5.4 engine, there is a few that have a higher gear such as I think a 3.08?? that is great for fuel mileage, but POOR for any type of towing!

What year is the F150?

Here's the link to a REALLY great spot...

http://www.ford-trucks.com/forums/index.php?s=