Warning! This page is for information only.   If you want to modify your steering and axles take you vehicle to a qualified fabricator and let them do the work.  If done improperly you could not only loose your life you many take others with you!  

Axle theory

This page is about front axles, the front axle decision is the most important decision you will make solid axle swapping your IFS truck.

First off, get rid of brand loyalty, that is the biggest mistake I see in solid axle swaps (looking at you Toyota guys). Branding is just plain stupid, frankensteins are the best, you can pick and choose the best OEM components for each part of your solid axle swap and have a bulletproof setup for wayyy cheaper then if you have some sort of bullshit brand loyalty thing going on. Some axles are just inherently flawed, weak and have no business being modified. I have seen “built” Toyota axles throw pinions on lightweight trucks with 22re’s when bound up and stock superduty axles under the same truck, powered by a V8, get undercut, bounce, hop and not break.  As a rule of thumb, if you want a strong axle just pull one out of a one ton truck and stick it in a small truck.

The second mistake is worrying about the width of the axle ie:  WMS. Fullsize axles are great on small and medium sized trucks, with factory rims (the best IMHO) they can often times not stick out far. Placing a narrow axle, with a similar WMS to your IFS is a waste of money and time. IFS trucks have wide frames for mounting the control arms, by placing a solid axle underneath, your tires will rub your frame and you cannon even turn full lock!

The third mistake is buying the wrong axle, many folks end up with bad axles because they did not research what axle makes for a good donor and get stuck with a junk axle. Buying the used, solid axle is one of the cheapest and easiest parts of a solid axle swap.

What is the meaning of High Pinion, Reverse Spiral, Reverse Rotation?

Ford was the first company to offer factory 4×4 trucks in 1959. A few years after the first factory 4×4 Ford launch, Dana, Fords axle supplier, released the first high pinion axle, 44RS, for production in January 1965.  This new axle has an oil slinger and passage tube to lubricate the pinion bearing which was submerged in previous designs. This axle has also been called the Dana 44 High Pinion, Dana 44 Reverse Rotation, Dana 44 Reverse Cut, Dana 44 High clearance and many more names.  The high pinion design offers a major strength increase over a standard rotation axle while in forward movement

-High pinion, this allows the for better driveshaft clearance, angles. This helps your U joints to last longer and keeps your driveshaft out of rocks. It is harder to package from an engineering perspective so many manufactures went with low pinion.

-High pinion applies torque to the correct side of the ring gear teeth when used in a front axle, the drive or “flat” side. Low pinion axles apply torque to the coast or “curved” side of the teeth, which is ~30% weaker because it is not triangulated properly. Low pinion axles apply torque to the correct side in rear applications and high pinions do so in the front. 

Imagine if all the water was on the dry, curved, side of the hoover dam and not the flat side, it would crack and water would flow out.

COMMON DONOR AXLES

Toyota mini-truck axle 79-85 passenger drop

Advantages: Strongest for the size, they are well engineered, can take good abuse and hold up, easily serviceable 3rd member, lightweight, strong axle shafts, strong lockouts.

Disadvantages: Expensive, rare, narrow Width, low pinion, small knuckle ball kingpins like to loosen and require periodic adjustment, small ball style knuckles that like to bend and difficult to service. Unlike a Ford 9″ third member they do not have the pinion in double shear, so they can deflect, strip pinion gears and throw pinions.

Toyota FJ80 FZJ80 91-97 passenger drop

Advantages: Most are High pinion, some come with E lockers, all feature a massive 9.5″ ring gear, serviceable 3rd member, strong kinpins with large knuckle balls, lightweight for its size, Reverse steer to help keep tie rod out of rocks, lockouts are an easy swap.

Disadvantages: Expensive, rare, reverse steer increases loading on tie rods doing go fast stuff. Unlike a Ford 9″ third member they do not have the pinion in double shear, so they can deflect, strip pinion gears and throw pinions.

Jeep Cherokee Fullsize 44 axle 1974-1983 passenger drop

Advantages: Cheap, no casting in axle tubes

Disadvantages:  Rare, low pinion, not so strong knuckles, undersized balljoints, hub nuts like to loosen and require periodic adjustment.

Jeep TJ 30 axle 1997-2006

Advantages: Cheap

Disadvantages:  Narrow, extremely small ring gear, super tiny axle tubes, no factory provision for locking hubs, undersized balljoints, low pinion, weak unit bearing design.

Jeep TJ 44 axle 1997-2006 driver drop

Advantages: High pinion

Disadvantages:  Narrow, expensive, rare, super tiny axle tubes, no factory provision for locking hubs, undersized balljoints, low pinion, weak unit bearing design.

Jeep JK 30 axle 2007-2015 driver drop

Advantages: Cheap, high pinion, stronger then previous Dana 30 models

Disadvantages:  Extremely small ring gear, super tiny and thin axle tubes, no factory provision for locking hubs, undersized balljoints.

Jeep JK 44 axle 2007-2015 driver drop

Advantages: Cheap, high pinion, stronger then previous Dana 44 models

Disadvantages:  Super tiny and thin axle tubes, no factory provision for locking hubs, undersized balljoints.

F100 & F150 44 axle 1976-1977 driver drop

Advantages: Disk brakes, Strong Axle, Welded radius arm wedges, High pinion

Disadvantages:  Rare, weak knuckles, undersized balljoints, hub nuts like to loosen and require periodic adjustment.

F100 & F150 44 axle 1978-1979 driver drop

Advantages: Disk brakes, High pinion

Disadvantages:  Rare, weak knuckles, weak cast radius arm mounts for a really weak axle tube, undersized balljoints, hub nuts like to loosen and require periodic adjustment.

F250 44 axle 1978-1979 driver drop

Advantages: One ton disk brakes, high pinion, strongest axle tubes ever to come on a Dana44 (1/2″ wall), heavily reinforced ribbed differential casting, strong spindle.

Disadvantages:  Rare, expensive, thin knuckles, undersized balljoints, hub nuts like to loosen and require periodic adjustment.

F350 60 axle 1978-1979 driver drop (was the best prior to 05+ superduty)

Advantages: One ton disk brakes, 35 spline inner, high pinion, strongest axle tubes (1/2″ wall), heavily reinforced ribbed differential casting, kingpins, strong spindle, locking hubs.

Disadvantages:  Extremely rare, expensive, thin knuckles, 30 spline outers, hub nuts like to loosen and require periodic adjustment.

F350 60 axle 1985-1991.5 driver drop

Advantages: One ton disk brakes, high pinion, 35 spline inner, strong axle tubes, reinforced ribbed differential casting, kingpins, strongest serviceable hubs to date, locking hubs.

Disadvantages: Expensive, 30 spline outers, narrow drivers axle tube, hub nuts like to loosen and require periodic adjustment.

Dodge Dana 44 axle 94-01 driver drop

Advantages: cheap, common

Disadvantages: Central axle disconnect weak, low pinion, small 32 spline inner shafts, cast axle tube can break, undersized balljoints, small brakes, poor unit bearing design, weak axle tubes. No capability for locking hubs.

Dodge Dana 60 axle 94-99 driver drop

Advantages: cheap, common

Disadvantages: Central axle disconnect weak, low pinion, cast axle tube can break, undersized balljoints, small brakes, poor unit bearing design, weak axle tubes, no oem capability for locking hubs, small 32 spline inner axle shafts.

Dodge AAM axle 03-05 driver drop

Advantages: cheap, high pinion

Disadvantages: Undersized balljoints, poor unit bearing design, weak axle tubes, no capability for locking hubs, undersized balljoints.

2001-05  Ford super-duty axle driver drop

Advantages: Cheap, common, locking hubs, good brakes, high pinion, locking hubs

Disadvantages: Undersized balljoints, poor unit bearing design, narrow drivers axle tube, weak 30spl outer axles and locking hubs.

2005+  Ford 60 super-duty axle (SUPER 60)(the best you can get and longest running design to date, DANA and Ford got it right with this puppy)

Advantages: Cheap, common, high pinion, strong ball-joints (bout damn time), strong knuckles, strong unit bearing design (yay), strong 35 spline axles, big brakes, factory 35 spline lockouts, stout axle tubes.

Disadvantages: lots of casting material to cutoff for a custom application, weird bolt pattern, extreme drivers side drop and nonexistent drivers axle tube.

Back when I did my solid axle swap, in 2010, there were less “good axles” to choose from we had the 1978-79 F250 Dana 44’s for a stout 3/4 ton axle with 1/2″ thick wall tubes and the F350 78-79 for its kingpins, stout design and long driverside axle tube. A good 78 79 Dana 44 axle cost around $600-1000 and a Dana 60 version of around $1300-1900.

Today, that has changed thanks to International’s major design failure with the 6.0L diesel engine in Superduty Ford trucks. You can find a front for $600-800 and a set, with rear axle, for around ~$1000-1200.

Ford and IH rushed this POS engine to market, they wanted to have the most powerful, cheapest and most emissions complaint engine to date; so they cut corners.

Checkout the absolutely insane architecture of the ford 6.0L, it only has four headbolts per cylinder, like a gasoline engine. No diesel engine with only four head bolts per cylinder has been reliable ie: Cat 3116, Detroit 8.2L.

Since there are many, many junked 05+ superdutys the axles are plentiful and cheap, yay!

The 05+ superdutys are the best out there

-35 spline factory outers

-Massive balljoints

-large axle tubes

-Rear Sterling axle is stout thanks to its long pinion.

-High pinion

So what makes a good axle?

-35 spline vs 30 spline speaks for itself, most Dana 60’s only have 30 spline outers, but not the superduty Dana 60.

Knuckle size, small knuckles will tear balljoint holes, crack and break.

Look at how thick the casting is around the balljoints and perimeter of the knuckle.

See how thin the casting areas are on Chevy kingpin knuckles.

The disadvantage of the Superduty axles are:

-Short Drivers side axle tube, can make packaging difficult for anything but coilovers.

-Metric everything including the bolt pattern. Remember, there are two types of countries: Those that use the metric system, and those that have landed on the moon.

-The long pinion on the Sterling rear axle can make packaging a driveshaft with a short wheelbase vehicle impossible.

So what would be the ideal solid axle?

-High pinion, double shear pinion, removable 3rd member (lightweight), giant open kingpins.

Well, it does not exist but you can get damn close with an ULTRA-14HP and some custom stuff……

EXOTIC AXLES:

For the guys n gals that like them thicc, these axles are not highway friendly, made by the lowest bidders, but when you gotta run the big tires, these are the shit yo. Military axles may be the strongest and many of the trucks that run them are capable of  driving high speeds, but continuously driving above 50MPH will cause major issues, especially in the summertime and a guarantee in the southwest.

Unimog 404 Portal axle

Advantages: Most produced portal axle in the world, lightweight, simple design, factory mechanical lockers.

Disadvantages: Undersized upper kingpin that wears out fast, poor casting design that can crack at wheel ends, drum brakes, does not enjoy running at high speeds, loves to randomly blow out hub seals.

 Unimog 406, 419, FLU portal axle

Advantages: Robust, factory mechanical lockers, giant kingpin ends, newer ones have disk brakes

Disadvantages: Heavy, expensive, does not enjoy running at high speeds.

Rockwell 2.5 ton Toploader axle

Advantages: Common, inexpensive, kingpin, close knuckle ends, big axle shafts.

Disadvantages: Open diff, Antiquated, hates sustained highspeed driving, eats through seals.

Rockwell 5 ton Toploader axle

Advantages: Common, kingpin, close knuckle ends, big axle shafts.

Disadvantages: Heavy, open diff, hates sustained high-speed driving, runs hot, antiquated design, often leak and eat through seals(pinion, hub), replacement air wedge brake parts extremely expensive.

Meritor RF-611 FMTV Bevel axle

Advantages: Common, Robust kingpins, great steering angle,  lightweight and high clearance thanks to bevel gear reduction in hubs.

Disadvantages: Runs hot with sustained high-speed driving, replacement wedge air brake parts extremely expensive, difficult to service.

AXLETECH 4000 MRAP Planetary axle

Advantages: Common, excellent steering angle, high clearance thanks to planetary gear reduction in hubs, uses conventional air brakes, air locker.

Disadvantages: Heavy, Difficult to service, runs hot with sustained high-speed driving.

50 Ton Clark Planetary

Advantages: Monster trucks!

Disadvantages: Creates its own gravitational pull.

Aftermarket axle housings and carriers:

In my opinion, based on installing and running aftermarket 3rd members and axles into hundreds of off-road vehicles under companies I have worked for, you cannot beat the maintenance free nature of OEM, used axles.

Why?

-Cheaper

-In many cases they are more reliable. The OEM axles are supplied in hundreds of thousands of units, designed by professional Tier 1 automotive suppliers using FEA and tested millions of miles before they ever make it on a vehicle.

-Aftermarket axle stuff leaks, overheats, wears out in a few thousand miles and can fail in deadly ways.

-Aftermarket axles are good for the race coarse, stock axles are good for not killing a bus full of nuns.

AFTERMARKET AXLE shafts:

Many times, “cheap” aftermarket axle shafts are weaker than regular OEM axle shafts due to they way they are manufactured. They have improper fillet radaii and create major stress concentration. Often times the metallurgy is poor; information is fake and incomplete.  Look for manufactures that neck down at the same level as the inside cuts of the spline, are made in first world country’s, and have professional, independent, 3rd party data to back up the strength of the shafts.

Steering:

Factory steering is usually the best for geometry but not the strongest and places your steering in the way of obstacles.

Many aftermarket companies offer solutions (high steer, double shear and relocation kits). Some are horrible as the place the steering in single shear, and/or relocate the steering arm in a crazy location. Anything single shear is a no-no, keep all your steering double shear always when using heims.

Knuckle steering kits are great but usually if they use the factory knuckle steering holes, anytime it is moved it screws up the Ackermann steering geometry which will cause your turning radius to decrease and tires to slip and fight eachother when turning. Your Ackermann should be modified when you change wheelbase from the factory vehicle the axles were donated from. The line between pivot point at the balljoint and your tie rods should intersect at your rear axle.

Good examples of double shearing and/or relocating  your steering.

This will increase strength, relocate your steering out of harms way and provide factory like handling characteristics.

Poor examples of relocating steering (in terms of geometry).

This one places your Ackermann out into the space on the sides of you vehicle, very bad… these are sold like hotcakes.. for some reason.

This will cause your vehicle to wander on the highway, not want to return to center after turning and have a horrible turning circle with your tires fighting each-other.

Likewise, a homebuilt example

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