14 bolt or a 10.25.
14 bolts has caddy discs with parking brake. not sure about the internals yet. it was sitting under a house for awhile.
10.25 also have a disc brake kit not installed.
both will need a good through to set them up.
i have options
All that matters is what you are going to do with it, what ratio will you run, and what locker will you buy.
If you are going to run it with custom brakes, geared and spooled, then it doesn't matter...and you are basically buying iron. Use the one that weighs more.
The vasts majority of people are making the choice between the 14 bolt, the 10.25, and the D70 as a "junkyard axle" decision. For this reason, the primary driver is cost. When your budget is $300, then you want the strongest, easiest, and most available axle. The proper choice has been the GM 14 bolt since 1973. And the reason is because you could get a full detroit locker as a drop in for $200. Couple that with 1-9/16 axle shafts, and the ability to change WMS by changing hubs, and the ability to shave the pumpkin...and the fact that the CUCV came factory / military surplus with 4.56 gears and a Detroit locker and a the 14 bolt is the clear winner.
Fast Forward to 1984, and Ford FINALLY built a 10.5 ring gear and a decent axle and put it in the F250 behind the 6.9 Diesel. The Dana 70U with a Power Lock and 35 spline axles was almost as durable as the 14 bolt, and pretty decent. But it's a heavy pig, with giant drum brakes. But in a crawler, it's a good choice. The Sterling 10.25 is basically the same axle, and they are all in the same 10.5" category. The AAM 10.5 falls in the same family.
So who cares? If they are all 10.5 nominal ring gear, (10.25 is close enough to 10.5) then what's the difference? The difference is in failure modes. Rear axles fail for 3 reasons. Shock load, Max torque, and wear. With the advent of high torque diesel power, a 10.5 ring gear is necessary to propel a 3/4 ton truck down the highway under load. So everybody makes a 10.5 rear axle. And any hypoid gear set looks the same. But with high shock load, and big torque...pinion deflection becomes important. The GM 14 bolt is the clear winner for pinion deflection under torque. And also the winner for impact loads. and also the winner for the biggest axle shafts (at 1-9/16 vs 1-1/2)
As soon as you open you wallet and decide to get a selectable locker, custom gears, and custom brakes...then you've totally changed the game. And in a lightweight vehicle, it's really hard to beat a fabricated 9 inch running full float 40 spline gun drilled axles on a full spool. But that's where weight is the driver.
So the answer to the rear end question is always the same, and has been the same since 1973. GM 14 bolt for the win.
