I own an f250, 7.3 deisel that has had the complete rear end
swapped out, (due to wreck damage) i am not sure that the
correct ratio rear end was put back in the truck...help

serial no. Of truck: 1FTNW21F73EA84022

tag on rear end: S 409 b, l731058e22, 75w140 synth oil only

can anyone help me?

 

Here are the codes for the 250. You can look on the door for the tag that has specs, on of which is the axle. That code should be one of these, to tell you what you had.
27 – 3.31 Non-LS
26 – 3.73 Non-LS

Maybe someone can decipher the number from that rear end tag, but I can not. What you can do is jack it up and see how many times the drive shaft rotates in relation to one wheel turn. Less that 3 1/2 would be 3.31, more than 3 1/2 would be 3.73.

 

Bluejay, thanks, problem is there is no info on door tag. I will do the
jackup/count turns thing. Thanks again... Gterry

 

Has the tag been removed? There should have been a sticker type tag on the edge of the driver's door, with several items listed, one of which is the axle code. If it's been repainted, maybe it was removed.

 

According to the rear end tag, you have 3.73 LS in there. That's what the "L73" means. The "105" indicates a 10.5" axle.

 

Yes, the truck has been repainted. I jacked it up and checked. One full turn
of the wheel equals 3.73. My reason for checking this is that my information center says i am getting around 19 mpg, but when i check it,
i actually get 12 to 13 mpg. Any thoughts?