Axle swap

randomname

member
Mar 30, 2019
5
1
3
Utah
I just installed F31 Deavers on Kartek Drop Hangers and Camburg extended shackles (on a stock 01 XLT 4.0), and I'm looking to do an axle swap to get the rear end ready for a bed cage and real shocks. I've done a bit of researching but I keep finding myself in a rabbit hole of shit when it comes to axle swaps. I see most people swap for an Explorer 8.8 for the strength and disc brakes (also ease of swap), but have heard a bit about the 9" Ford but not any specifics. I've also read that a spring under setup is better on the springs themselves, and will prevent axle wrap and get better up travel, but when I see axle swaps most run in the stock spring over configuration, even with the 8.8 explorer axle which is a spring under configuration. Is there really any reason besides ride height that people don't stick with the spring under?

I read that if you do anything serious with the 8.8 you will replace it every few years, and that the 9" is the most desirable. I've also read not to get the 9" until you link (I imagine because its not a straight swap), but I would rather do it right the first time and not have to go through the bullshit of swapping the axle as scheduled maintenance. I can't find much info on the 9" besides a 76-77 Bronco as a donor for the 31 spline instead of 29. Those still run brake shoes, so I understand you have get a kit for the disc brake conversion. Also, with the 9" you have to get a locking differential kit, and I've heard about the super 88 kit as well, but I am not sure what I will really need.

I'm basically just stuck in a loop with what I should get for my truck. A lot of that info comes from a Jeep forum, but I'm not building a rock crawler. Also the DR rides build threads help, but they just say they swapped with X without much info. Assume I want to run class 7100 BITD eventually when I get everything built. What should I do to get it done right the first time. Can anyone point me in the right direction?
 

sirhk100

Racer
Feb 24, 2003
16,216
131
63
Las Vegas
If and this is solely IF you truly really are going to be racing in 7100 and want to be competitive spend the money and have a quality housing built. We started on a currie 9" semi floater with spool and 35 spline shafts. Bent it and snapped shafts. Stepped up to a fabricated floater housing with big hubs and still 35 spline shafts. Fixed issues with that upgrade but still have shaft life limitations. It's fun though and we run reasonably hard. Won the mint a few times and the championship a few...
 

Turboyota

Senior Member
Mar 29, 2017
2,682
607
113
Yucaipa
Explorer 8.8 PROS:

1. Direct bolt on. Spring perches, driveshaft flange, VSS(or whatever the hell that sensor is on top), and brake line all bolt right up. 5 on 4.5” bolt pattern. Only caveat is the parking brake cable bracket needs minor modifications to be usable.

2. Cost. Exploder 8.8’s can be found for $100-$400 depending on gear ratio and differential type. They can be sourced with a decent gear ratio (4.10, I believe or maybe even lower) and a limited slip differential.

3. Aftermarket support. Desolate motorsports makes an awesome truss/diff cover and many other companies offer nice upgrades.

4. Relative strength. Strong enough for F150’s, Broncos, and other moderate prerunner applications. 31 spline axles help.

Explorer 8.8 CONS:

1. Narrow
2. Failure-prone C-clip setup
3. Axle tubes can pull out of the center section if abused


If you can find an Explorer rearend that will suit your needs until you start racing, do it. Don’t pour money into it, though—that’ll eventually be money wasted.

If you start racing, dont mess around and plan on buying a 40 spline setup from Camburg, Schreiner(budget option), or the swapmeet.

——————-

Ford 9” swap considerations:

1. Driveshaft will need to be modified or replaced. $200-$800 depending on myriad factors.
2. Vehicle speed sensor or tone ring or whatever the hell it is will have to be addressed. CalPreFun and others offer kits...
3. May as well upgrade to 5on5.5” bolt pattern, so front will need to be changed at the same time.
4. New brake lines
5. Parking brake will likely be gone
6. New tabs for everything
7. Do this upgrade when linking the truck
 
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bri_man57

Need to Build
Jul 11, 2005
2,533
31
48
32
Ventura, California
He is running f31s so he would need to relocate the axle perches to the top anyway. Wouldn't want to run 31s in spring under.

It's easy to want to go crazy at the beginning of a build, been there, done that. My take is explorer rear ends are not a bad gig. I had a ranger 8.8 (28 spline) with a full case Detroit locker in it that never gave me a lick of trouble. Drove to the desert and back countless times, not 1 issue. I'm not easy on my truck, not race hard on it, but not easy. I don't land on the throttle from a jump though.

The c clips don't bother me, I feel like the crosshaft bolt breaks, allowing the cross shafts to move, then the c clips drop. All the failures out group has had was from that. I think since mine had a full case locker, that stuff was different and probably why I never had an issue.

I have also read that stock 8.8 axles are made from a stronger material than junkyard 9" axles are.

If I were going to build an axle from scratch (axles, brakes, gears, locker) it would be a 9" no question. If I was trying to slap a better rear end in, 8.8 that already has gears. Like said, don't dump a bunch of cash into an 8.8

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96f-u250

Senior Member
Sep 27, 2013
801
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VenTurA 805!
if you go with the 8.8, get it from an e-150, its a couple inches wider than the f-150 and you can upgrade the front to 5x5.5
 

doyouquaxu

Asshole Member
Feb 12, 2007
32,313
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Texas
If your end goal is to race, do a 9" swap. Also, your F31 Deavers won't hold up to the rigors of racing. You'll need to G50 pack at least, or a Giant 64 kit if you can do a full replacement leaf system (I'm not up to date with the rules of the class you're looking at). Both the F31 and G50 springs are designed for spring over applications similar to stock, so you'd have to weld the spring perches on once and be done for both sets. The Giant kit is spring under like the Explorers are from factory.

I ran an explorer 8.8 in the back of my first ranger with F31 Deavers and it was awesome. Simple swap, like stated because the two rigs are so similar. My second ranger had a Giant 64 kit and a full size 8.8 from an F150 or something. Still was a pretty straight forward swap, just had to get the driveshaft end from the donor truck's driveshaft to put on my ranger's so it would bolt up. Brake line fittings are all the same size iirc. Both are fucking cheap options to pick up from a junk yard on 1/2 off weekends. Lots of aftermarket support, and replacement parts for trail fixes are at every autoparts store.

My last truck ran a custom 9" housing built by Camburg and finished by Currie Enterprises. The custom route is awesome because it's exactly what you need, but is expensive. I bought parts during holiday sales, off ebay, and giving good old fashioned hand jobs for parts discounts. It was built to the exact width I wanted, the gears I wanted, diff I wanted, set up for the links or leaf springs I wanted, and completely perfect. Really fucking expensive though. Easily over 3k for everything.
 
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randomname

member
Mar 30, 2019
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Utah
He is running f31s so he would need to relocate the axle perches to the top anyway. Wouldn't want to run 31s in spring under.
To run spring under is the F31 just not enough? Would I have needed that G50 or the Giant 64s? Or is it not really necessary if you get the rear set up correctly?

My plan is to build in stages, and I've heard you can send in the springs to Deaver and they can upgrade and tune them (to basically a G50) for when you go full cage and start adding the weight of the fuel cell, tires, tools, etc. in the rear.

Anyway, so I have found an Explorer at the junk yard, it's a 2004 I think with 4.10 ratio. I do want to run 35's so I wanted to change the gearing to 4.88. So I should just get that, swap it in with a normal spring over config, and be done with it for now? When I get the rear set up with a full cage than I'll worry about dumping money into it?
 
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garrettw

Member
Mar 23, 2015
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San Clemente, CA
So I should just get that, swap it in with a normal spring over config, and be done with it for now? When I get the rear set up with a full cage than I'll worry about dumping money into it?
👍🏻 Do it. Odds are you’ll have more fun in the desert with that setup than on a set of jackstands waiting for parts. And when it comes time to upgrade, cut the back off and link the fucker. As for “doing it right the first time” talk to Geoff at Giant about that, if I woulda listened to him my truck probably would have seen dirt this season😅
 

bri_man57

Need to Build
Jul 11, 2005
2,533
31
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Ventura, California
F31s are not made to be ran spring under, they don't have near enough arch. If you did spring under, you would have a stupid low ride height. People that run spring under have springs that enough arch to do so. The benefit of spring under isn't because it's spring under, it's because the springs have so much arch that you HAVE to run spring under. G50s are spring over, giant 64s are spring under but come with all custom brackets. Regarded as the best set of leaf springs for rangers as well as other trucks, but you're gonna pay for it.

I'm not knocking your build plans, everyone sees these types of trucks and wants to race. My recommendations lately come from a spot of not wanting someone to get in over their head and not use their trucks cause they are waiting for parts. You want to race 7100, awesome. Are you building to that stage right now? (Be honest with yourself)

I wanted to race back in the day, but after realizing how much coin it takes to maintain these things, the time involved, how much it costs being an adult, I just don't see me racing off road. I much prefer cruising around the open desert.

If it were me, unless you are going full race truck build immediately, slap in an 8.8 with at least 4.10 gears, don't spend any money on it after that, then build a 9" in the background. If you truly end up racing, a few hundred bucks on a rear end to keep you going won't kill the budget. Keep it together, keep it in the dirt. You'll have more fun.

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