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Building Stout Ford Half-Ton Bronco Axles for Off-Roading

Posted in How To: Transmission Drivetrain on November 21, 2016
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Why is this story titled “Short Range”? Because most would probably rather lick a hot branding iron than take an extended road trip in a single-cab, four-banger Ranger shod with 35-inch tires, 5.38 gearing, a rear spool, and no air conditioning. But, believe it or not, that’s exactly what we were aiming for with our 1998 Ranger: slow and technical trail capability sprinkled with some short-range “bouncing around town” ability.

And no, we didn’t actually do a solid-axle swap around a campfire, but this is—in our experience—where some of the best (or most ridiculous and 100 percent unattainable) plans are forged. For us, “campfire building” plays out the exactly the same way almost all the time: The lighter the cooler gets, the more solid, feasible, and cost-effective our ingenious (at the time) plans become. But when reality strikes the next morning, building a personal nuclear-powered submarine would likely be an easier proposition than whatever we devised the night before.

I’m not sure if it’s because we are sick of lying to ourselves or we have officially become seasoned campfire bench-racers, but we finally managed to forge a plan within the realm of reasonability from (nearly) start to finish. This time, while sitting around the fire at Rocky Mountain Terrain Park in Carthage, Maine, after a day of wheeling, the plan in question—revolving around stronger solid-axle options for our buddy’s 1998 Ranger—quickly took shape. Right out of the gate the discussion’s trajectory was headed down the same harebrained flight path as usual. However, the course deviated 180 degrees after another buddy piped up about excavating a Dana 44 front and Ford 9-inch rear axle set from under the rusty remains of a 1974 Bronco. We were pretty sure the overall width was in the ballpark. We knew they could be made to fit and were plenty stout for the intended application. To seal the deal, it came in at the right price, an 18-pack of a frosty adult beverage. The deal was locked in around the campfire, and the tired factory TTB Dana 35 front and Ford 7.5-inch rear axles were relieved of duty shortly thereafter.

Like any campfire build, there were some hurtles, but all in all, this is a relatively simple and straightforward build that a lot of readers could tackle at home. Since we were out of pocket $0 for the donor axles, our plan was to put the saved coin directly back into the axles and suspension. With conservative 35s as our target tire size, the goal was to keep the stance as low as allowable to maintain stability. With help from James Duff in the suspension department (more about that in Part 2) our solid-axle conversion should be a walk in the park. Conveniently, since the buddy who owns the Ranger is one of the lead technicians at one of the larger repair facilities in town, Auto Care Plus, all the work was completed in a nice, clean, well-equipped shop.

Since the Ranger’s wee 2.5L four-cylinder would be rendered next to useless by 35s with the original 3.50 gearing of the Bronco axles, taller gears got pushed to the top of the parts list. G2 Performance Series ring-and-pinions and install kits got the nod both front and rear; forged from 8620 steel and cut to factory specs, these gears represent an outstanding value for the money, helping keep costs down on what was originally planned out as a budget build. The ratio we chose was 5.38:1, which will give us a crawl ratio more than adequate and, in turn, may make those four little pistons under the hood seem a little larger than they actually are.

Rear 9-Inch
Instead of working with the rear’s 41-year-old, 100,000-plus-mile factory 9-inch centersection, our buddy decided to spend a little extra dough and got his hands on a brand-new nodular iron unit from G2. Reinforced with increased ribbing and added material in all the areas that count, it will no doubt handle anything the Ranger can dish out. Even though we are only stepping up to 31-spline axles from the factory 28-spline, we opted for the 35/40-spline-compatible carrier with the larger 3 1/4-inch bearing journals to lay the foundation for future axleshaft upgrades. To make this work, we needed the requisite Timken conversion carrier bearings to make up the difference in diameter, which we sourced through Quick Performance. For budget reasons—as well as simplicity’s sake in a mostly off-road rig—we also assembled our 9-inch carrier using a 4140 billet-steel G2 31-spline full spool for an inexpensive fulltime-locked rear differential. While it doesn’t get any more simple, rugged, or reliable than a spool for guaranteed all-wheel traction off-road, the handling quirks, tire wear, and ever-present tire squawk during parking lot maneuvers do not lend themselves well to everyday street driving. We didn’t care; we have chest hair.

Shortly after assembling our carrier, we looked into ordering a pair of chromoly axleshafts to put a “done” stamp on the rear. Here’s where the biggest hiccup in our plan erupted. Because the donor Bronco used a small-axle-bearing, 9-inch rear housing, it was not able to accept any of the larger, 31-spline, large-bearing aftermarket axleshafts without making a compromise. This left us with three options: We could run a conversion axle bearing of questionable longevity that would allow a 31-spline shaft to be run in a small bearing housing; we could weld on aftermarket big-bearing housing ends to the axletubes of the housing we had; or we could buy a brand-new housing and axle kit and call it a day.

Since the first option didn’t leave us with a warm and fuzzy feeling, and welding new housing ends onto the axletubes can get kinda tricky without a fixture to hold the ends square while welding heat is applied, we hit the easy button and got in touch with Currie Enterprises to get our hands on one of the company’s 1966-1977 Bronco Crate Rearends. The Currie kit comes with everything you need (minus the assembled carrier and brakes), including a Currie 9-Plus housing; 31-spline induction-heat-treated 1541 alloy axleshafts with bearings, seals, and backing plates preinstalled; and heavy-duty leaf spring pads and shock mounts. To button up our now totally new 9-inch, we bolted on Currie’s 11-inch drum brake kit, which comes with the brake shoes and hardware preassembled onto factory Ford backing plates.

Said and done, our 9-inch won’t know the Ranger is even atop it, let alone trying to kill it. True, the original plan of using the salvaged Bronco 9-inch didn’t pan out, but a little extra money spent here will pay dividends down the road—especially if the four-popper under the Ranger’s hood get swapped out for something more substantial.

Front Dana 44
Redirecting our efforts up front, the Bronco Dana 44 was stripped to a bare housing, media-blasted, and painted in preparation for assembly. For at least some level of steering when four-wheel drive is engaged, our front locker of choice was the supremely bulletproof Eaton Detroit Locker. If you’re not familiar with the Detroit, it’s is a fully-automatic locker that replaces your ring gear carrier in its entirety, and when torque is applied in a straight line, the ratchet mechanism of the Detroit locks both drive wheels. When you are turning or letting off the gas, it unlocks. During tight steering maneuvers when a full-time spool would cause the front end to push and give you the turning radius of an ocean liner, we have found the Detroit Locker will allow momentary unlocking and vehicle redirection simply by working the gas pedal. And since our Dana 44 has selectable hubs, the Detriot will go entirely unnoticed on the street with the hubs disengaged anyhow.

With our axle assembled and the ring-and-pinion engagement shimmed to perfection, we plunked in a set of forged, 30-spline G2 Tork front axleshaft kits, assembled with Spicer cold-forged 760X U-joints. Finishing touches included a complete Early Ford Bronco disc brake conversion kit from Bronco Graveyard, which includes everything needed to ditch the drum brakes in one convenient kit, and a set of G2’s new inexpensive, rugged, lifetime-warrantied locking hubs.

All told, we ended up spending more coin on these axles than we anticipated—and on top of that, the only part we actually used on the salvaged Early Bronco axles was the front Dana 44 housing. But look on the bright side: It wasn’t a fail. It was just a more-expensive win. Oh well. We’ll be making the axle-to-Ranger marriage in the next installment, so stay tuned!

The platform for our solid-axle swap was this much-loved yet well-used 1998 Ranger, a great package size for negotiating tightly wooded New England trail systems. Riding on a worn-out 4-inch-lift suspension, mostly spanked 33-inch mud terrains, and the tired factory locker(less) TTB Dana 35 front and 7.5 rear axles, it was due for a reboot.

One of the terrible yet sometimes handy things about living in New England is the abundance of rusted-out, vintage 4x4s just waiting to donate their drivetrain goodies. Our salvaged Dana 44 front and 9-inch rear, excavated from beneath this thoroughly Swiss-cheesed 1974 Bronco, were had for a song. Actually, it was an 18-pack of a frosty adult beverage that ultimately sealed the deal. You gotta love campfire negotiations!

Since we were stepping up to a 35-inch tire with no immediate plans to replace the tired little four-popper under the hood, we needed substantially taller gearing than the factory 3.50 ratio of the donor Bronco. Because of their outstanding value—and for what should prove an ideal crawl ratio—G2 forged Performance Series 5.38 ring-and-pinion sets and install kits got the nod here.

For a clean slate we decided to spend a little extra dough on one of G2’s nodular iron differential carriers, which feature increased ribbing and material nearly everywhere. They are offered in two carrier bearing sizes: one for 28- and 31-spline axleshafts, and the other for 35- and 40-spline shafts. To set the stage for future powertrain upgrades, we chose the big one. To make it work with the 31-spline shafts we wanted to run, we got our hands on the requisite conversion carrier bearings. This is where our plan hit a pothole.

Since running 31-spline shafts in the small-bearing housing ends of our Bronco housing meant either using conversion axle bearings of debatable longevity, or the tricky procedure of welding on new large Torino-style housing ends, we hit the easy button and ordered up one of Currie’s 1966-1977 Bronco crate rearends. The Currie 9-Plus heavy-duty housing that comes with the package is built to factory dimensions and ensures we are starting with a much stronger and 100 percent straight platform. We had Currie leave the spring perches and shock mounts off so we could burn them in according to our Ranger’s factory spring/shock locations.

Included with the Currie crate rearend is a set of 31-spline performance axleshafts fully loaded and ready to slide in with the backing plates, bearing retainers, seals, and wheel studs all preinstalled. Forged from 1541 alloy steel and induction heat treated, they’ll be oblivious to the fact that our Ranger is attempting to murder them.

Comparing the factory 28-spline Bronco shafts to our new 31-spline Currie shafts, you can almost hear James Earl Jones reciting Arby’s “We have the meats” slogan. The strength added by stepping up in spline count is pretty obvious. Along with the shaft diameter and stronger material, the fully assembled Currie performance axleshafts also give you thicker quarter-inch bearing backing plates, as well as thicker wheel flanges.

The single domino effect of swapping 9-inch housings was that our original small-bearing drum-brake backing plates no longer fit. Currie offers several disc and drum brake options, but to help keep costs down we chose the company’s standard 11-inch drum brake kit to button things up. The kit comes with new 11-inch drums and with all the brake parts fully assembled onto reconditioned and powdercoated factory-Ford backing plates. About as easy as it gets.

With our third member locked, loaded, dialed in, and bolted in, we were ready to rock and roll with final assembly. Currie preinstalls the mounting studs for the third member, and everything from here forward is a simple bolt-in. We also took the opportunity to run the hard lines for the brakes while the entire housing was out in the open and easily accessible.

Outside of our 30-spline Detroit Locker, G2 was a cost-effective one-stop-shop for our Dana 44 front axle centersection build. We also ended up using G2’s Hammer heat-treated aluminum diff guard to protect the work and money put in here, as well as G2’s impressive (both in cost and construction) new locking hubs.

Just like the rear, we were able to get the pinion depth, bearing preload, and backlash of our G2 ring-and-pinion dialed to perfection relatively easily and quickly. Worth a mention if you’re tackling a similar job at home: A Yukon Gear & Axle carrier bearing puller made all the difference in the world. We wouldn’t be caught setting up a differential without one now.

Making the connection between the Detroit Locker and the G2 hubs is a set of 30-spline G2 Tork axleshafts. Available separately or in assembled kit form with Spicer 5-760X U-joints (shown), the forged, induction heat treated Tork shafts are built to exceed the strength of O.E. shafts without the high cost of going chromoly. Like the rest of the G2 parts we used here, they represented a pretty smart value for our Ranger.

Since sticking with the original Bronco drum brakes on our Dana 44 front axle really wasn’t an option, we sprang for a 1966-1975 Early Bronco front disc brake conversion kits from Jeff’s Bronco Graveyard, to which we added new Timken wheel bearings. In the kit you will find everything you need to ditch the drums, including hub/rotor/wheel stud assemblies, caliper brackets, caliper hoses, spindles, spindle bolts, and rebuilt and loaded calipers—whole shootin’ match. Finally, we buttoned up the axle with a set of G2’s new locking hubs.

Shining like a gold-tooth grin, our Early Bronco axles are said, done, and ready to be slung up underneath our Ranger. True, we kinda shot holes in the budget by scrapping the salvaged 9-inch, but thanks to some of G2’s high-value parts, we were still able to keep overall build costs reasonable. With the help of a radius-arm suspension system from James Duff, our solid axle conversion will become more than a campfire pipedream in Part 2.


Currie Enterprises
Corona, CA 92880
Cleveland, OH 44114
Spicer (Dana Aftermarket Group)
Toledo, OH
G2 Axle & Gear
Compton, CA 90220
Quick Performance
James Duff
Sequim, WA 98382
Bronco Graveyard
Yukon Gear and Axle
Auto Care Plus

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