Ok guys, I know this topic has been touched on a couple time but I just need a little more clarification. I just figured out how to decode my VIN and come to realize I infact do not own a "highboy"... (maybe, i think, i still don't know). Anyway, the axle code on my 1977 F250 is B4J.

B4 (rear axle)
ratio: 4.10
capacity: 5.3M
Make: Dana (spicer)
Model: 60
Description: Limited slip

Now who can fill in these blanks?

J (front axle)
ratio:
capacity:
make:
model:
description

 

Oh, and what does "capacity" refer to?

 

Best way to ID the axle is the tag on the differential cover .. Record that number/letter combo and report back .. see here for Highboy ID related stuff

 

"J" means it's equipped with power steering.
Capacity is how much weight the axle is designed to handle. Ford, for some unknown reason, "sorta" uses Roman numerals in their capacity ratings. 5.3M means 5300 lbs capacity. "M" in Roman numerals is 1000.
Even though the last digit in the axle code is supposed to refer to the front axle, it rarely actually had anything to do with the axle itself. The last code usually is for power steering (J) or tilt wheel (A). There are other codes for power steering and tilt wheel but those are the most common.

 

Thank you Mike for the J code clarification. It was really starting to bug me. I guess I will have to look a little harder at the front axle itself to figure out more of what I need to know.

And a bittersweet thank you to you Redroad... Your link for highboy identification was enormously helpful!!! However now I am certain I do not own a "highboy" as my vin is in the Y45000 area. :-((( Oh well, I still love my purchase. Now to figure out how to change my username... LOL