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JK Wrangler Front Axle Fail - Jp Magazine

Christian Hazel Brand Manager, Four Wheeler Photographers: John Cappa

Have a JK Wrangler? Running big tires and heavy wheels? Wheel it? Yes? You’re hosed. Lately it seems that nine out of 10 JK Wranglers with bigger tires or heavy armor have a bent front axle. That goes for 2WD all the way up through the Rubicon models. It’s more prevalent in the heavier four-door Unlimiteds, but the two-doors aren’t immune. Furthermore, stuff like the front ball joints, track bar bracket, and sway-bar brackets are normally hashed. The rear axles are a different story, so we’ll focus on the fronts here.

jk Front Fail wrenching On The Trail Photo 32444597

When the JK Wrangler came out in 2007 it addressed a lot of the shortcomings of its TJ predecessor. Better suspension and steering geometry, improved stability and handling, and even upgraded axle strength (in some areas) are all now in its playbook. The pedestrian Dana 30 front is high-pinion for better gear tooth contact in a front application. The Rubicon Dana 44 front is high-pinion with a bigger 8.8-inch ring gear, a larger pinion, and larger 1350-size axle U-joints. Both use the same knuckles with much better steering geometry and huge 12-inch brakes. Sounds good, right? Well, it’s all packed into a housing that’s as frail as a 90-year-old woman. Thankfully, the aftermarket has addressed many of the issues and there are solutions. But there’s no free lunch. Before throwing metric tons of money into your factory Mopar axles, consider your ultimate build plans, wheeling style, and level of abuse so you can build appropriately the first time.

Other Stuff
Many other aftermarket manufacturers are jumping on the JK axle-fix wagon. Here are just a couple offering components to upgrade and bolster the JK front axle.

JKS Manufacturing: Heavy-duty brackets
Skyjacker: Bolt-on lower control arm skidplates
RCV Performance: CV-style chromoly axleshaft assemblies
Poly Performance: Heavy-duty replacement ball joints; 3-inch axletube kit; heavy-duty brackets
Reid Racing: Heavy-duty replacement knuckles
Superior Axle & Gear: Chromoly axleshafts

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The unitbearings aren’t an inherently weak component in the JK front axle. Dynatrac’s Jim McGean says his company has done calculations that determine rim offset with heavy tires is more damaging to the bearings than impact. So if you’re running wheels with shallow offset and heavy tires, the increased leverage is more likely to effect wear or damage than jumping and or regular off-road abuse. Either way, periodically check your unitbearings.

The JK Dana 30 uses 1.16-inch, 27-spline shafts with 760X-sized U-joints. The Rubicon 44s run 1.31-inch, 30-spline shafts with a larger 1350-size joint. Dynatrac’s McGean warns the Rubicon Tru-Lok electric front locker employs an offset centerpin, so unique-length axleshafts are required if retaining the stock locker. Some aftermarket shafts don’t address this issue, so check against the stock shaft length before you plunk in your new units. Furthermore, McGean warned us the cost of a replacement Tru-Lok has skyrocketed to $1,800 MSRP. If you buy aftermarket shafts to work with your Tru-Lok you can’t use them with an aftermarket locker, so if gnarly wheeling with big tires is your forte, you may want to consider upgrading the locker when you buy your shafts.

Mel Wade of Off Road Evolution says his company’s Magnum 44 axletube sleeves increase strength 30 percent. The sleeves employ dual greasable seals to help keep debris out of the axletubes and are an inexpensive way to bolster the strength of the stock Dana 30 or Dana 44 axle. We’ve seen bent passenger-side long-tubes on stock JKs, so at only $159.99/pair, if your housing isn’t already bent we think they’re a great solution to the budget-minded JK owner not planning on huge tires or extreme wheeling.

Another weak point in the JK Dana 30/44 housings is the spindly inner knuckle C. To bolster the factory housing, Off Road Evolution offers its C2 Gussets that weld to the upper and lower portions of the inner C. The C2 gussets run $89.99 for a full set of four. The company also offers 3⁄16-inch control arm skids that weld on to the 0.125-inch-thick factory brackets to help prevent damage and improve strength.

Despite gusseting and sleeving, severe use on a heavy vehicle can eventually lead to catastrophic failure of the housing. As the front axle articulates, the four-link brackets torque and twist the axletube. With time and heavy use the steel of the stock tubes can fatigue and crack, shatter, or simply snap.

On the factory axles (top), many shops report cracked or broken track bar brackets, broken sway-bar tabs, and even ripped lower control arm brackets. The ProRock housings (bottom), whether standard or Unlimited, feature Dynatrac’s hugely thick inner Cs, heavy-duty brackets, and centersection that has a heavy-duty casting and more ground clearance than a Dana 30.

To control quality, in the past Dynatrac built the entire axle assembly. That’s still true with the ProRock 60, but with the pressing need of the JKs, the company now offers the Dana 44 in different levels from bare to loaded with aftermarket gears, locker, and shafts ready to accept your JK knuckles and brakes. All ProRock axles use Dynatrac’s much-improved 3⁄16- to 1⁄4-inch brackets. The ProRock 44 uses the same pinion angle relative to caster (6 degrees separation) as the standard Rubicon housing. With factory Mopar ball joints, you can get this housing for under $2,000. However, if severe wheeling or taller suspension is in the works, the ProRock Unlimited can be had with either 3x0.375- or 3x0.500-inch tubes and increases the pinion angle relative to caster (10 degrees separation).

We’ve spoken with JK owners who balk at the cost of a replacement housing, but in our opinion it’s a requirement if you’re seriously wheeling a heavy JK with 35-inch or larger tires. One key factor for this is axletube strength. Compare the factory 2.5-inch-diameter, 0.250-inch-wall factory tube (right) with Dynatrac’s 3-inch-diameter, 0.375-inch-wall tube of the ProRock Standard (center) and 3-inch-diameter, 0.500-inch-wall tube of the ProRock Unlimited (left).

Many JK owners experience death wobble after running larger wheels and tires for a while. If adjusting the toe setting to 1⁄8-inch toe-out or upgrading the factory steering stabilizer doesn’t help, chances are that the factory ball joints are toast. The stock Mopar ball joints wear quickly, so it makes little sense to us to purchase replacement factory parts for $220 when Dynatrac’s ProSteer ball joints are available for $599 by themselves, or can be had as an upgrade to any ProRock housing for $499. The ProSteer joints are greasable, rebuildable, and have a heat-treated billet-steel body with Teflon-coated internals that will last infinitely longer than any factory replacement.

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JK Wrangler Front Axle Fail - Jp Magazine

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