Ford 9" Axle Housings That'll Bulldoze Dirt and Crunch Rocks
If you wheel long enough with the lovable Ford 9", you'll want to upgrade the axle housing.
The 9" has some great things going for it, but a fresh, wheeling-ready axle housing can make a big difference in setting up your axle and making it last.
So let's take a look at some 9" housings and what you want to think about when you buy one.
How Ford 9" Axles Break
While the 9" is strong, it won't hesitate to shred itself if you're hard on it.
If you're rockcrawling it, you can grind a hole into it.
If you're jumping or having hard landings, you can bend the housing, even if it's trussed.
We've also seen and heard of:
- Shredding gear teeth
- Grinding up the stock posi
- Busting the pinion bearing support
- Twisting axle splines
- Bent leaf spring perches
- Cracks around the third member face
- Blown out carrier bearing caps
- Twisted axle housings
- Broken carrier cross pins
Now, not all of these are 9" housing problems, but some certainly are! While we have some issues where parts just don't hold up to the horsepower, there are also lots of cases where a weak or bent housing can cause binding and breakage in other parts.
Why Get a Fabricated Ford 9" Housing?
There are a ton of fabricated 9" housings out there!
People want'em. The 9" has always been an extremely common, easy to build axle due to it's long use by Ford in a ton of vehicles.
Stock 9" housings are cheaper if you have one, but fabricated housings are just better.
You should buy a fabricated Ford 9" housing if you want:
- A lighter axle: We think picking off pounds is one of the best ways to wheel better and without breakage. Little savings add up.
- More strength: It should go without saying that a 4x4 9"aftermarket housing will be stronger than stock.
- More ground clearance: This is built in to any housing used for wheeling.
- A clean (unbent!) housing for welding on brackets: Is your stock housing bent? Do you care about cutting stuff off it and pitting from rust?
- Easier fab: While you should always be careful about warping when welding an axle housing, the thicker tubes on a fabricated housing are far less likely to bend than the stockers.
The Ford 9" Housing vs. the Ford 8" Housing
The Ford 8" is very similar to a 9", although it is weaker and usually cheaper.
They look so similar that you should make really make sure that you aren't buying an 8" if you're taking a look at an axle.
Here's how to tell them apart quickly:
- The 9" has a vertical rib on the third member. Put yourself in front of the pinion and look at the third. If there is a vertical rib to the left of the pinion, it's a 9" axle. (The rib make the 9" stronger.)
- The socket trick: Put a 3" extension on a socket for the 9" third member studs. If the socket+extension won't fit then you have a 9". In other words, if you can't use the socket+extension on the bottom studs, it's a 9" housing.
- Without a carrier, you can measure the distance between the two bottom studs. On a 9", this will be 10". On the 8" this will be 8 3/4".
- The 9" axle housing is rounder at the top and the bottom, the 8" has longer flat spots on top and bottom and looks a little more oblong. Yeah, we know that this is pretty useless unless you've seen lots of 9" axles or you can compare them.
The Ford 9" Housing vs. the Ford 8.8" Housing
The Ford 8.8" is not the same as the Ford 8"! Also the 9" is not just an 8.8" rounded up!
The 8.8" and the 9" are similar, but harder to confuse than a 9" and an 8". It's noteworthy that a 31 spline 3.25" axle-tube Ford Explorer 8.8" axle is pretty close in strength to a 9". Overall strength is really dependent on the spline count and the 28 spline 8.8s don't really cut the mustard.
The most obvious differences between a Ford 8.8" and a Ford 9" are:
- The third member is not removable in the 8.8". This is super obvious.
- The 1995 and up 8.8s have disc brakes. '91-'94 8.8s have 10" drums. All 9" have drums, unless they've been swapped.
- Yeah, you should really just look at the third!!!
How Many Bolts Does a Ford 9" Housing Have?
The third member bolts on to the 9" axle housing with 10 nuts. The 9" housing uses 10 studs with a 3/8"-24 thread. You'll need a 9/16" socket and wrench to remove the third member.
If it isn't obvious, studs make it much easier to pull the the third member off, since it's fully supported by the studs while you slide it off.
The pinion support is typically secured with either 5 bolts or 5 studs.
The ring gear in a 9" axle bolts to the carrier with 10 7/16"-20 bolts. They usually come in 7/8" , 1" and 1-1/4" lengths, depending on the carrier that you use (1" for stock/open).
Why Is the Ford 9" Axle Special?
The Ford 9" has been around a long time: Production started in 1957 and went until 1986. It has been used and upgraded in every vehicle imaginable, from drag cars to Jeeps on the Rubicon.
They are cheap to acquire and have a huge aftermarket of parts that you can choose from.
You don't even need a 9" to start with:
You can buy every single part of a 9" on the Internet if you want!
Ford 9" Third Member
One of the most popular reasons for using the 9" is the drop-out third member.
While most axles have a removable cover on the back of the axle, the 9 inch's centersection can be easily removed by pulling your driveshaft, unbolting the 10 nuts that secure the third, unbolting the axle flanges, and slightly pulling out the semi-floating axle shafts.
It's a simple, strong design that makes it easy to swap gears, install a locker, or mess with something inside your diff.
No Carrier Breaks
The fact that the 9 inch has no carrier breaks means buying parts for it is much easier. Generally, carrier breaks are not difficult to deal with but they can be annoying and cost you extra cash if you have the wrong carrier. With the 9":
- You don't need to worry about thick or thin ring and pinion gears.
- You don't need to decipher axle codes, do research, or count ring and pinion teeth to see what your ratio is (assuming you're swapping gears) to determine your carrier break.
- You don't need to worry about whether lockers will fit.
- Any junkyard 9" will have the same carrier as any other 9".
A Zillion Parts
The Ford 9" has probably one of the most extensive selections of parts you could ever want. It's easy to build a complete axle from parts you buy online, or order a prebuilt axle to your door.
Because there are so many parts out there, your 9" can grow with your wheeling. Start out with 31 spline shafts, then go to 40 spline!
Superior Ring and Pinion Tooth Contact
Pinion to ring gear contact is better than it is on a Dana 60. This doesn't mean that your gears will never chew themselves up, but it's a better baseline of strength.
Huge Range of Gear Ratios
There are tons of gear ratios available for the 9", from 2s through 6s. This has to do with the huge aftermarket and makes it easy to change gears since there's no carrier break.
What to Look For in a Fabricated Ford 9" Housing
There are lots of Ford 9" housings out there to choose from. We're going to take a look at a few variations so that when you buy, you'll know what to look for.
Some features to look at include:
- Thick axle tubes: These replace the thin sheetmetal tubes of stock 9" housings.
- Axle width: It's easy to get housings with several different widths to fit your 4x4.
- Equal length axle shafts OR centered pinion: Equal shafts for carrying a single spare or a perfectly centered driveshaft.
- Thick, machined faceplate: This is where your third member goes.
- Keyed axle tubes: To prevent spinning.
- Space for a 10" ring gear: Want to run a bigger, stronger ring gear in your Ford 9"? No problem!
Ford 9" Axle Housings You Can Beat On
Trail Gear Rock Assault 9 Ford 9" Axle Housing
The Rock Assault 9 is probably one of the most "convenient" axles to buy if you want a variety of options delivered to you your door with a click. It comes completely bare or fully loaded - let's take a look at the housing specs first:
These housings are highly configurable on ordering so that you can get an axle that'll bolt into your rig in a weekend...
Without any machining!
The faceplate on these is a milled 1/2" plate. Like the RuffStuff housing below, the pumpkin is 1/4" thick and gusseted internally to put up with the twisting and abuse you'll put the housing through off road.
You've got three width options with this axle:
But make sure you know that Trail-Gear assumes your use of its unit hubs and 1/4" disc brake hats. These widths are WMS (Wheel Mounting Surface) to WMS, so the axle will be a little bit narrow to account for those other components.
You've got 4 total options for axle tubes:
- 1/4" wall tubes in 3" and 3.5" diameters
- 3/8" wall tubes in 3" and 3.5" diameters (we like light rigs, but are partial to beefy axle tubes)
This housing has a slight pinion offset of 2 1/8". This means that you can install axle shafts that are equal lengths, reducing the number of spares you need on the trail.
Like any good aftermarket housing, this one fits both 9" and 10" gearsets.
This axle comes in a number of different configurations. Here are three:
Rock Assault 9 with Bearing Pockets
This option gives you a bare housing. You'll notice that many 9" housing do not come with much on the ends, meaning that you'll need to figure out bearings and brake brackets.
Fortunately, this housing come with the bearing pockets already added at your required width.
No machining or worrying about welding pulling things out of alignment.
Rock Assault 9 with Axle Shafts
If you're just upgrading a 9" and you already have some parts sitting in your shop, check out the Rock Assault 9 that also comes with axle shafts.
Axles are Trail-Gear's 35 spline 4340 chromoly full floating shafts and they come in a variety of lengths.
Rock Assault 9 Roller Kit
If you're piecing together a 9 inch rear and you need a bunch of components, check out the Roller Kit. It has everything you need to actually roll your rig around the garage! (Hence the name.)
With this kit you get:
- A Rock Assault 9 axle housing
- Unit bearing hubs
- A seal housing kit
- Unit bearing pockets
- 14" brake discs
- Brake hats
- Wilwood calipers
- Caliper mounts
This is a pretty easy way to get most of the parts you need to build your 9"!
RuffStuff Specialties Ford 9" Axle Housing
This housing from RuffStuff is built for abuse!
Let's start with the beef, starting from the inside out:
The faceplate is 3/8" milled plate, cut to fit your 9" diff. They mill after welding so you don't end up with studs pointing at all angles.
The pumpkin is made from bent 1/4" steel that's internally gusseted. RuffStuff has made the centersection large enough that you can stuff in 10" gears if you want.
The axle tubes are actually keyed into the axle plate. This'll eliminate spinning tubes and creates a stronger welded joint.
If you want strength in a 9" housing, the standard is 3/8" thick steel tube in a 3.5" diameter. For flexibility, other manufacturers offer tube in smaller diameters, but RuffStuff only does the 3/8" wall/3.5"OD tube.
The axle is 72" overall and does not include any provisions for bearings.
One interesting feature is that you can order this axle in a couple of different faceplate configurations. One allows you to have a centered pinion and one allows you to have equal length axle shafts. Can't have both!
RuffStuff will also add on a bunch of other parts/reinforcement to this housing, including a top truss, back truss, armor, and/or a vent.
Plus, this housing is made in the USA with USA steel!
Currie Ford 9" Centurion Axle Housing
If you're that looks more "normal" than a fabricated rear, Currie has a line of 9" housings that'll do the job. This one is for '66-'77 Broncos with the Centurion housing.
The Centurion line is intended to follow the original Ford 9" housing appearance while still being suitable for hard duty.
The housing itself comes with billet large bearing ends.
This setup also comes with 31 spline Currie axles.
Currie F9 9" Axle Housings
If you want to go Currie, but you want the next step up, take a look at the F9 series of Ford housings.
These housings come with several different axle tubes from "small" to monstrous!
The tube sizes you can get are:
Most of these housings are available in both a steel and chromoly version.
These housings all have a 3/8" milled faceplate for mounting your third. The pumpkin on each unit is 3/16" thick - a little thinner than the 1/4" on the RuffStuff housing.
The axle tubes key into the centersection to eliminate tube spinning, plus the pumpkin, faceplate, and tubes have a ton of internal gussets to tie everything together.
Currie usually custom builds these housings to your specs so that you can get exactly the width and pinion offset that you want.
Of course, all these housings will fit the 10" ring gear.
Last updated: October 24, 2019