Christian Hazel
Brand Manager, Four Wheeler
Photographers:
Ben Battles
Of all the vintage pop-top rigs we see on the trail, the early Broncos are still some of our favorites. But like any horse getting long in the tooth, the old Broncos' legs just aren't what they used to be.
Back in the day ... hell, even back six or seven years ago, 33s were commonplace and 35s were considered a monster of a tire. The Dana 44 front and 28-spline Ford 9-inch rear axle found in later Broncos had little trouble coping with these moderately sized tires considering the off-road demands of the day. What was considered extreme wheeling back then is mild wheeling today. And those 33s that adorned every trail killer have given way to 37s, 39s, and even 40s. What's a Bronco guy to do?
When a buddy posed this question to us regarding running 37s on his '75 Bronco, our knee-jerk reaction was to point him straight at a pair Dana 60s. But then we got to thinking. With the right mix of aftermarket components, it's possible to make the stock axles survive running 37s or 38s. Heck, if he's careful, it's not out of the realm of possibility to keep 'em alive with 40s. So before you go and pull the trigger on your game pony, check out how we fix the deficiencies of the factory axles with the help of Jeff's Bronco Graveyard, Offroad Design, Reid Racing, and Drivetrain Warehouse.
Knuckles & Steering
Want to spot a Dana 30 from a Dana 44 from across the parking lot? Dana 44s have ball-joint knuckles, while Dana 30s have kingpin knuckles. Neither proves very impressive on the trail. The relatively weak castings of the factory knuckles are only the tip of the iceberg. Sharp eyes will note the lack of a flat top that can be machined for high-steer arms, often necessitating complicated bent drag links to work with lifted suspension. Thankfully, Reid Racing has upgraded knuckles for both the six- and five-lug Ford Dana 44 spindles, and Offroad Design makes beautiful high-steer arms that fit like a glove and that keep proper steering geometry with regard to Ackerman angle.
Although the six-bolt-knuckle Bronco Dana 44 front axles (right) came with drum brakes, it's possible to upgrade them to disc brakes and even aftermarket knuckles with Chevy, Dodge, or Jeep parts. Not so with the Ford-only '76-'79 five-bolt knuckles (left).
Front Axleshafts
We're all about one-stop shopping where we can find it. It cuts down on incorrect parts showing up at your door, and helps ensure your assembly goes smoothly. That's why you'll see the name Drivetrain Warehouse throughout this story. The stock shafts do OK with small tires, and can even hold their own with aftermarket rubber up to about 33 inches in diameter. However, once you add a locker and start getting after it, the limits of the stock shafts will be found in a big hurry.
Offroad Design has an incredibly nice set of four-hole high-steering arms that take advantage of Reid's fourth bolt hole. ORD's machining is spot-on, with the knuckles simply dropping right onto the studs. Normally there's some inconsistency and you've got to resort to the dead-blow hammer to make things fit. Not so here. The ORD arms have the right tapers drilled for use with stock tie-rod ends, or they can be drilled for 3/4-inch rod ends. Careful consideration was given to maintaining the full range of steering, spring, and component clearance when ORD designed these arms.
Front Gears & Locker
A Dana 44 will survive a surprising amount of abuse, but like anything, it has its limits. Big tires make big stresses, so if you're going to upgrade one part of the equation, you've got to upgrade the other parts as well to keep your axle assembly balanced. Otherwise, you create a fuse that, when blown, isn't going to be pretty. We tapped the Drivetrain Warehouse stockroom for the parts and pieces we'd need to complement our Superior front shafts.
Like the rest of the components going into our Bronco front axle, only a top-notch ring-and-pinion kit got the nod. Once gear ratios climb, pinion strength suffers. Genuine Gear's G2 ring-and-pinion is a precision piece that should help offset the inherent weakness of the smaller 4.88:1 ratio pinion. The Genuine Gear installation kit came with high-quality Timken bearings and all the shims, bolts, slingers, and marking compound we'd need to set up our own gears.
As you can see on the right, a factory Spicer open diff carrier and an easy-to-install lunchbox locker can become the weak link if your Dana 44 is running a real quality set of axleshafts and U-joints. To help guard against another catastrophic failure like this-and to provide traction to both front tires-we opted for a Detroit Locker. Its tough construction and trouble-free operation should provide years of service.
A Little History
Wondering what axles your Bronco came with? Here's a little helper.
Front
Axle: Dana 30
Found In: '66-'711/2 models
Notes: Drum brakes, small 260X-sized U-joints. Can be upgraded with aftermarket shafts and disc brakes, but it's better in the long run to swap in a later Bronco Dana 44.
Axle: Dana 44
Found In: '711/2-'75 models
Notes: Drum brakes, 297X/760X-sized U-joints. Six-bolt spindles easily converted to disc brakes. '711/2-'721/2 spindles utilize outer axle seal that presses into back of spindle. '721/2-'75 utilize outer seal that presses onto stub shaft.
Axle: Dana 44
Found In: '76-'77 models
Notes: Disc brakes, 297X/760X-sized U-joints. Five-bolt spindles are unique to '76-'79 Ford 1/2-ton Dana 44 axles so crossover of brands (Chevy/Dodge/Jeep) not possible.
Rear
Axle: Ford 9-inch
Found In: '65-'75 model
Notes: Small bearing housing ends with 3/8 bolts (backing-plate mounting-hole measurements 35/16x2 inches). 10x21/2-inch drum brakes. Driver-side shaft length 271/8 inches; passenger-side length 295/8 inches.
Axle: Ford 9-inch
Found In: '74-'75 models
Notes: Medium duty, large bearing housing ends with 3/8 bolts (backing-plate mounting-hole measurements 39/16 x 2 inches). 10x21/2-inch drum brakes. Driver-side shaft length 271/4 inches; passenger-side length 293/4 inches.
Axle: Ford 9-inch
Found In: '66-'75 models
Notes: Standard duty, large bearing housing ends with 1/2-inch bolts (backing-plate mounting-hole measurements 31/2x23/8 inches). 11x13/4-inch drum brakes. Driver-side shaft length 2615/16 inches; passenger-side shaft length 291/4 inches.
Axle: Ford 9-inch
Found In: '76-'77 models
Notes: Heavy-duty housing, large bearing housing ends with 1/2-inch bolts (backing-plate mounting-hole measurements 31/2x23/8 inch). 11x21/4 inch drum brakes. Driver-side shaft length 273/16 inches; passenger-side shaft length 2911/16 inches.
Rear Axle Upgrades
Although the '76-'77 heavy-duty housings left the factory with larger 31-spline shafts, most Broncos are packing spindly 28-spline shafts. While they'll do for moderate wheeling, it's a sure snap in the making to run them with big tires and a locker in the rocks. Once again, Drivetrain Warehouse had the parts in stock we needed to upgrade not only the shafts but the factory gray steel carrier as well.
The Five-Bolt Curse
When we decided to convert our buddy's front axle from six-bolt to five-bolt we didn't know what we were getting ourselves into. We thought we'd just drop by the local wrecking yard and nab the five-bolt spindles, backing plates, and other stuff we'd need to make the swap. Long story short, after much scrounging through boneyards, craigslist, and eBay, we dropped by Jeff's Bronco Graveyard. That is to say, we dropped by Jeff's Web site. There, staring us in the face was a complete kit for the five-bolt Ford Dana 44 axle with everything we'd need and more. The company is super-knowledgeable about these trucks and quickly had everything we needed out the door to us.
The Jeff's Bronco Graveyard Extreme Outer Rebuild Kit (PN 12213) included everything we needed to convert our buddy's six-bolt Dana 44 with the exception of the caliper brackets. But wouldn't you know, JBG had a set of those as well. The kit is too nice for words, and includes new spindles, Timken bearings, seals, studs, ball joints, calipers, high-performance cross-drilled and slotted rotors, spindle nuts and washers, and everything else you see in the photo.
