well, I have been robbing the parts I need from the old 85 6.9l idi for my 4x4 conversion on my 90 7.3 idi, I opened up the rear diff cover on the sterling 10.25 to check things out and to my surprise it has an open diff and not a limited slip as stated on the door jam sticker as a C9 axle, so I'm searching for a limited slip carrier case for now, now, my 90 truck has a sterling 10.25 with an open diff (2wd) and the 85 has the same, if I did buy a limited slip carrier cases will it drop in place of the open diff on my 90 10.25 without having to change anything else? are all the carrier cases the same for the 10.25 from 85-91? do i have any other options on this?
thanks Tilly

 

While my F250 was down, getting a back half of a frame swap a few years ago, I decided to pull the diff cover to drain and inspect things. To my surprise, the open carrier was snapped in half! It was still working, noise free, didn't even know it. I probably snapped it, twitching logs over the years.
I figured I'd swap in a LS unit while I was replacing it. Found one locally and bought a carrier bearing and shim kit. Left the pinion installed. It's not for the faint of heart, but if you watch enough videos and a couple articles, you can set it up. Ideally, you'll reman the whole thing (not necessarily the ring and pinion if they're ok, but the pinion bearing too and that's a whole job in itself to set up) while you're in there, but I didn't because that's not what failed and I figured it would be good for many more years, so far, I was right.

The added bonus I noticed right away, was just how much more beefy the whole carrier is! I ain't snapping this one!

Most folks will leave this level of job to professionals and although I can see why, I also realized why I hadn't changed gears in a rear over the years, was simply because I didn't try, not because it's a job any shade tree can't do......although I'm sure much, much, much slower, especially for a first time, who cares? Worked fine for me, as that truck was down waiting to go truck shop for welding, so. Was a great opportunity to finally learn. Of which a lot of it I've already forgotten haha but I wont fear it anymore.

You have a lot of aftermarket options, from air lockers, to reaching retrofitting in modern e-lockers (which would probably be killer!) to lockers (best for off road use), to units that don't use friction discs like Eaton Detroit Truetrac, which is likely the very best solution if you wanted to get real serious.

Mine is 4wd and has always had all the traction I wanted, I was happy the score the used LS unit, even if the clutches wear out, I gained a major upgrade in strength I need for twitching logs. That unit and the kit from bronco graveyeard, I think I was in just a couple hundred bucks and it's been great for a few years now.
My "off roading" for my tree service trucks is generally grass, so haha. Your needs may vary greatly, although with a 2wd, they probably shouldn't.

You'll have to research what year carriers you can swap, but it's a lot of them, if not all.
Take this quick google search with a grain of salt and do your own, but I'm getting "'85 to 2010 are interchangeable" - without digging into things enough to trust that. I do seem to recall, that I could have swapped in an e-locker, but I don't recall what, if any modifications where required to do such (other than running up some wire to the cab and installing a toggle switch of course), but pretty sure I could have. I just didn't see the need for my truck.

Side note, and you should find this out in your own research too, you'll notice in '93 they updated the yoke to a long style. It's stronger (though it's no problem for oem size tires) it's when you get lifts and tires where it can fail. Still, if you do reman the whole thing and swap out the pinion bearing, do upgrade to the long yoke while you're at it. I would have done so, or will do so, when that time comes. My truck is a '93, but I have a '89 DRW axle under it.


If you do things right, you'll spend 10 to 20 times the time researching than it will take you to swap carriers and set it up.

Or of course, you can just cheat, like I used too; swap whole pumkins in Ford 9" or whole rear units in trucks. All you need a junkyard rear with the right gears and LS and some new u-bolts. For SRW 10.25's you'll probably score a whole rear for less than you can reman the unit yourself with used carrier, and install kits (bearings and shims). Remember; never re-use u-bolts! The threads are rolled, not cut. They are one time use only.
I wasn't able to cheat this time, due to DRW truck rears being very pricey. You likely can. I probably should have lead with this haha.
Search your local yards and or car-part for local and distant yards ( Listen! Before they ship a rear, MAKE them verify it's what you want; ideally a '93+ [but don't pass up a good deal for an older one] rear with gears your after and LS, the only sure way to know is force them to pull the cover and look for you) and u-ship for shipping quotes. If you have a Traction store (it's like a Napa for big trucks) they make up U-bolts.

 

thanks for such a good in-depth write up mate that was really helpful, i will re-read it over again to take it all in then do a bit of researching, thanks again mate much appreciated

 

I suggest you replace Pinion Bearing & Seal if you're going this far, since you pretty much have to set it up again anyway.
I prefer the solid, shimmable, spacer in place of the crush sleeve on the pinion.
Locktite 660 on the splines, Locktite 272 Orange on the Pinion Nut.
Install Pinion nut with small Impact driver as you select Shims for proper preload. Keep in mind big Impact will be compressing shims a very small amount. I stall Seal, butter splines & threads up with Locktite, and run that puppy down with the big Impact.
You can notch out & drill a long piece of angle iron to bolt on Yoke to keep it from turning. I get lots of free angle iron from old bedframes....
My procedure is to leave seal out while I'm sellecting shims, install seal before final assembly and tightening.
Crush sleeve just always works loose eventually and you cant truly crank down on the Pinion Nut to keep it all together, especially with DRW or big tires.

 

even if the axle had LS, after 41 years it would now be an open diff anyway..... u less it only has 10,000 miles on it.

 

The used one I picked up works great. The guy had a great big lifted 4x4 dent side (Blue and really nice shape with a built 460!) and decided to put something heavier duty in it and didn't even use it himself. He just picked it up used somewhere too. You can buy replacement clutches too of course to rebuild them.