difference in ford 9'

[305chevy c-10]

what's the best ford9"  rear end ?there is a 3.5 ,2.75 and a 3.25 axle tubes i think with big bearing 31 spline or 28 .

[Captkaos]

An aftermarket one not made by Ford.  You want the biggest axle with the most splines for strength.  Tube size generally dictates axle size.

What are you doing with it?

[305chevy c-10]

no major racing just playing in the street a little(ok alot )  .just thinking ahead maybe in the future when this HP bug bite it may make me want to go a step futher in my build .i also want to run some really wide tiers out back maybe like 14 '' wide on a 20" wheel /18"x9 up front .i know thats alot of rubber out back and i dont know if a 10 bolt will handle that much with out blowing a pion seal or something .i mean i may not even have enough motor for them either .i'm just thinking

[HAULIN IT]

The 2.75, 3.25 & 3.5 are all common gear ratios for a 9". There are several different axle tube sizes (none are 3.5 though). There are Two different sizes of center housings - up to 3" use the "small shoulder" one that has basically butt welded on tubes & the center on housings with 3 1/4" tubes are much larger & the tubes slide inside it. There are axle splines in 28 & 31 stock, along with both small & big axle bearings.
To answer your question...A "large shoulder" housing with 31 spline & the big axle bearings would probably be what most would concider "the best" factory set-up. If you plan to have it narrowed much, stay away from an early-mid '70's coil spring housing...they have the tubes flattened on the top & effect the narrowing process.
Here's a photo of a "large shoulder" housing...it's about 26" from weld to weld & notice how the tubes slide inside the center. On the small unit, the tubes & center are the same with just a weld bead bump. Hope this Helps, Lorne   

[305chevy c-10]

thanks guys  .thats just the info i needed to know

[305chevy c-10]

so the large shoulder one ,if i grind the welds off i should be able to pull the tubes out or push them in for the correct width .by chance do u remember ur flange to flange /perch to perch centers specs

[HAULIN IT]

so the large shoulder one ,if i grind the welds off i should be able to pull the tubes out or push them in for the correct width .by chance do u remember ur flange to flange /perch to perch centers specs

Basically...Yes, however it's not just that easy. The axle bearing "cups" need to be lined up VERY accurately to have the axles, bearings, tires, ect. live. A 1/16" off here (either in toe or camber) is allot when you factor dealing with a 26"-28" tire going around @ xx MPH for many miles. The fact that you are welding Two feet from the end makes it likely that the end moves around while welding.
What you need is a way of holding/aligning the parts while/during the welding. There are a couple ways...The best is a large bar riding on the carrier bearings & a set of "hubs" to align the axle bearing cups. Another way is a large, thick plate with plates mounted 90* & parallel to each other to hold the ends still. This could work well if someone was making a bunch of the same length housings.
Here is a picture of my set-up...Bar through the center & a hub on each end to hold the bearing ends in place.
This is really something best left to somebody with the right equipment...I have fixed many housings built without a jig after several repeated bearing or axle shaft failures that weren't all that far off. You should be able to have this done for something between $100 & $200.
The flange to flange measurement is only relevant if using the same backspaced wheels. The perch to perch number would be the same as factory unless your going to move the springs. Hope this helps you understand it a bit more. Lorne
    

[305chevy c-10]

ok thanks it helps

[scorpion]

If you're looking to go to the yard and get one you can narrow without thinking, pull one from a 1983 - 1986 Econo-Line Van.  They're over wide (meaning wide enough to narrow including resplining the stock shafts), always 31 spline, always have the Banjo Housing, have the largest diameter tubes, and come with the pinion yolk you will want.  Best part is they are too wide to work in any other ford so they're frequently even in the picked over yards.

The only downsides, I might add, about using the 9-inch ford is that throwing power at them can cause leaking issues around the third member, and the pinion support in factory cases have been known to fail during wheel hop situations.