9" F100- rebuild or replace with late model?

[motzingg]

I've been putting off dealing with my axle for awhile. Ever since swapping to the 5 speed it sees a lot more abuse being driven up to 80 mph regularly and it was already on the way out...

The wheel bearing finally went and now I've got to do something about it.

All the bushings are shot. The leaf springs are shot (warped) the differential itself needs new bearings (gears seem fine) and it obviously needs new wheel bearings. Just about every single part of it needs to be replaced or reconditioned... bummer.

It looks like about 300 bucks worth of bearings, plus whatever the leaf springs being rebuilt, and that still leaves me with no posi, weak springs, and an axle that is 2" too narrow and makes the truck look dog-legged. I've also got the smaller u-joint yoke on there right now, and I want to buy a driveshaft to use the larger u-joints, since the M5r2 output shaft can use them.

Replacing it with a later model junkyard axle solves most of these problems, but requires rewelding the spring perches (I have no problem doing this) and may require other things that I'm not forseeing, I.E. problems with the springs not fitting the old hangers, ride height, brakes, etc.


I am thinking, from my research, that if I find an axle from a Dentside or early-mid 80's F-150 or Bronc, It should be pretty straightforward. I have a guy who has a '84 bronc that i could measure. It could get me posi, 32 splines, and an all around better rear end for less than the cost of the bearings, But it would still be used and therefore somewhat unknown, and it would be a slightly more involved project, although might be less likely for me to screw up since i'm not 100% comfortable rebuilding a differential by myself.

I also have a spare 32 spline 3.0 gear 3rd member sitting on the shelf, not that it is a deciding factor, but its always good to have spares.


Anyhow, has anybody done this? any advice? My truck is used for light-moderate towing. Its a 68 F100 with a 4.9L and M5r2 swapped from a '91. When i'm all said and done, i'd like to be able to tow a car trailer without breaking a sweat and not ever worry about my differential not being up to the task. I don't think i NEED the 32 spline, but being 2wd I do think the Posi would be a worthwhile upgrade, nothing more frustrating than being stuck on wet grass in a 2wd truck spinning one wheel.

[motzingg]

hmm ok so i dug up an old thread where i was trying to figure out what would swap from an 80 bronco and it looks like i'm looking for 73-86 FSB or F150 axle with an L code in the tag.

I seem to remember something about there being an indication of locker/nonlocker on the door jamb tag? i'll have to do some research and see if that is true and what the tag is.

[tac]

You shouldn't have any trouble towing with standard 9", but a posi would be nice if you get off the pavement when it's wet. You can get a whole rebuild kit for $100 minus the wheel bearings.

[ultraranger]

'66-'77 Bronco was the original body style. Bronco didn't become full-sized until 1978, ('78/'79) body would have the same rear end as the '73-'79 F100, '75-'79 F150.

Most '73-'79 F150 rear ends have 31-spline axles/differentials. Traction-Lok was optional.

By 1980, all Ford F100/F150 9-inch rears had 31-splines, Traction-Lok was optional. --some 1980-1983 F100s had 9-inch rear ends with 5-on-4.5" lug pattern.

All factory Ford 9-inch rear end production ended by the close of 1986.