Gear & Axle - Pros & Cons - Four Wheeler Magazine

Ken Brubaker Senior Editor, Four Wheeler

Every OE axle has advantages and disadvantages. With that said, it helps to know what an axle’s strong and weak points are so you know what you can leave alone and what needs to be addressed.

To delve into this we pointed our truck to Custom Differentials in Bloomsdale, Missouri. This 20-year-old shop is owned by Jeremy and Pat Naeger, and these brothers have 45 years of combined experience in all things axle-related. Their fully equipped shop allows them to work on all sizes of axles, from the small stuff to heavy-duty commercial and industrial axles. Custom Diff-built axles have appeared under numerous vehicles featured on the pages of Four Wheeler and Jeremy is a Top Truck Challenge Champion and participant in Top Truck Champions’ Challenge.

We spent some time at Custom Diff, talking about and inspecting six popular axles found in fullsize trucks and SUVs in an effort to identify the major pros and cons of each. The six axles we selected are a mix of front and rear axles that are very common OE axles that many of you might have under your rigs. We’ve listed what rig each axle is most commonly found under, but some may be found under other rigs (including non-fullsize rigs) as well, sometimes with slight variations. What you’ll see as you read on is that some have more good attributes than bad, while others require a fair amount of attention. Here’s what we found.

Dodge Dana 60 Front Axle
Found in: ’94-’02 Dodge Ram ¾- and 1-ton trucks

Pros:

• Thirty-five spline inner axleshafts (though some ’94-’97 axles were 30 spline).
• Stout ring-and-pinion.
• Stout ring-and-pinion bearings.

Cons:

• Unit bearing failure. These expensive bearings can fail in as low as 80,000 miles in stock applications and far less in axles fitted with larger tires. Fix: One option is to replace the factory units with Moog unit bearings. They’re more expensive than a factory unit bearing, but they come with a three-year warranty. Another option is to install a hub conversion kit like Dynatrac’s Free-Spin kit that includes beefier, serviceable bearings.
• Ball joint failure. Similar to unit bearings, larger tires cut the life of the ball joints dramatically. Fix: Moog makes lifetime warranty ball joints, or you could install heavy-duty units like Dynatrac’s ball joints.
• Axleshaft U-joint failure. The design of the Dodge Dana 60 allows the axleshafts to spin whenever the truck is moving, which can cause the U-joints to wear at a faster rate. Fix: Spicer makes an alloy U-joint that is much stouter than stock and it comes with a lifetime warranty. Another option is the previously mentioned hub conversion kit that allows you to unlock the frontend.
• Axle-mounted shift actuator failure. These axles use an axle disconnect system and it could be operating slowly, incompletely, or not at all. Fix: Begin by checking the vacuum hoses for damage from engine oil or dry rot. If the vacuum lines are OK, it could be worn out internal items like needle bearings and/or bushings. Sometimes parts of the system can be repaired, while other times the entire unit may need to be replaced. The company 4x4 Posi-Lok also makes a cable-operated system to replace the actuator.
• The passenger side axletube can bend. This is due in part to the design of the axle, which incorporates an opening for the axle disconnect system. When the axletube bends it can also damage the axle disconnect system. Fix: Most Dana 60 owners don’t bother beefing the Dodge housing, but it can be done externally.
• Rust on the stub shaft threads. Trying to remove the castle nut with rusty stub shaft threads can gall the fine threads. Fix: Use penetrating oil and then clean the threads prior to removing the nut. Unfortunately if the threads are damaged the stub shaft must be replaced.

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Chrysler 9.25 Rear Axle
Found in: Dodge ½-ton trucks from the early ’70s to current

Pros:

• Large ring gear.
• Large ring-and-pinion bearings.
• Large wheel bearings.
• Strong housing that is not prone to bending.
• Thirty-one spline axleshafts.

Cons:

• C-clips retain the axleshafts.
• Aftermarket 3.55 and 3.90 ratio gears can be noisy. Factory gears are quieter, but more expensive.
• Trac-Loc limited-slip differential failure. The clutches are small and they tend to chatter and break. The clutch retaining clips dislodge and can damage the passenger side bearing cap. Fix: The Trac-Loc can be rebuilt, but it’s better in the end to replace it with a quality aftermarket limited-slip differential or locker.
• Pinion bearing failure. This is due to a design flaw that doesn’t provide proper oiling. Fix: There’s not a lot of options here, but a larger diff cover to increase the fluid capacity can help keep lube temperature down.

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Ford 8.8 Rear Axle
Found in: ’82-up F-150 pickups

Pros:

• Good strength-to-weight ratio.
• Tough, reliable housing that isn’t known for bending.
• Thirty-one spline axleshafts.

Cons:

• C-clips retain the axleshafts.
• Traction-Lok limited-slip differential failure. It’s very weak, doesn’t have many clutches, the cases wear, and there are no retaining clips for clutches Fix: Install an aftermarket limited-slip or locker.
• Diff lube leaks from the pinion yoke splines. This is due to the design of the pinion yoke, which doesn’t create a snug fit. Aftermarket yokes often have the same problem. Fix: Silicone the splines inside the yoke.

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GM 8.25 IFS Axle
Found in: ’88-up ½-ton IFS trucks and SUVs

Pros:
It’s light weight.

Cons:

• The 8.25 differentials from ’88-’98 used an overly complex thermal linear actuator (TLA) to engage the front axle disconnect and it is prone to poor operation and failure. In ’99 GM started using a new actuator that solved the problem. Fix: The manual, cable-operated 4x4 Posi-Lok is one option, or the guys at Custom Differentials can retrofit the new actuator to the older diff for approximately $250.
• Axle seals in the pre-’99 version are prone to leakage. GM switched to an improved system in ’99 that significantly reduced leakage, but unfortunately they’re not backwards-compatible.
• The retaining clip on either of the two threaded nuts that hold preload pressure on the carrier can break allowing the threaded nut(s) to unscrew, which allows the carrier to walk side-to-side. This problem is very likely in AWD vehicles because the frontend is under load all the time. Fix: There is nothing that can be done proactively (short of disassembling the differential and inspecting the clips) to stop the clips from breaking and it is likely that the resulting damage will require a total rebuild of the axle
.

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GM 8.5 Rear Axle
Found in: many ’78-up Chevy ½-ton trucks and SUVs

Pros:

• Like the small-block Chevy of differentials, the “10-bolt” has strong aftermarket support.
• The ’88-up version has the largest wheel bearings of all 8.5 axles.
• With strong aftermarket support you can make everything better except for ring-and-pinion size.
• The ’99-up version received larger carrier bearings.

Cons:

• C-clips retain the axleshafts.
• Weak housing, which if it bends can destroy the open or Gov-Lok differential.
• The Gov-Lok differential is very weak and when it breaks it can destroy the axle internals and even break the carrier in half.
• Smallest ring-and-pinion out of most ½-ton axles.

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AAM 11.5 Rear Axle
Found in: some ’00-up GM ¾- or 1-ton, Dodge ’03-up ¾-ton and all dualie 1-ton

Pros:

• Full-float design.
• Large quantity of these axles in use.
• Larger version of the Gov-Lok differential in the GM axles, the factory Dodge limited-slip differential is an AAM unit.
• These axles will go well over 100,000 miles before needing a rebuild, even under hard use.
• All are equipped with disc brakes.
• Great load carrying capacity.
• Large ring-and-pinion.
• Large, strong wheel bearings.
• The axle holds up well when fitted with larger tires.
• Good aftermarket support.

Cons:

• Parts are more expensive than comparable axles.
• The GM Gov-Lok has a high failure rate.
• These axles have a quirk where lube can leak from between the sleeve and the yoke. Fix: Unfortunately, the best fix is to replace the yoke with a new one. The price varies on these depending on what yoke is used.

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