Words and Photos by Bryan Irons @Bryanirons
No true off roader has gone for a trip in a newly acquired vehicle and proclaimed, “Perfect, I’m not going to change a thing.” Those people are what grizzled, dirt-eating wheelers term “quitters.”
We’re always looking for ways to enhance durability, driveability, off-road prowess or any number of reasons to drop more time, money, love and attention into our steel bundles of joy. Often, the very next upgrade is the axles.
These can be ordered to your exacting specifications. Your vehicle can be dropped off at a shop and modified, you can order all the upgrade components you want and spend some time in the shop, or like our predicament this time around, we have the money to spend on a traction adder, and we just want to get back on the trail.
What we have in front of us is a Dana 44 that a friend of ours started upgrading, but lost his way. The intention was to swap out the original open differential and install something with more traction. The 4.10:1 gears had been installed some time ago and were in great shape with the ratio working for the rig and tire size combination. Once the axle was out and opened up, he lost track of shims and tolerances, and decided that we could help. What are friends for? Luckily, he had left the pinion shaft and pinion bearings untouched, so we accepted his offer of a rejuvenated beverage fridge in our shop as partial payment.
In the heartfelt path of “there’s a butt for every seat,” we feel the same way when it comes to traction adders in differentials, except open differentials can all stay at the mall. For this situation, an Eaton Truetrac was selected to suit the mild off-roading and daily driver application this rig was going to see.
The Truetrac is a helical gear design that attempts to keep both wheels with an equal amount of torque applied to them, until that amount greatly varies between both sides of the axle. On the street, we have run Truetrac’s with no adverse handling repercussions and they provided ample torque when among the dirt and rocks. They really shine on snow- and ice-covered roads, but if your adventures see you pushing massive amounts of power, mammoth sized tires, or you hang a tire in the air frequently, there are better choices.
We certainly trust the Truetrac for exacting tolerances, but the installation kit reeked of no-name brand bearings and shims made of Play-Doh and dreams. There’s no point in throwing trash parts in an axle since an axle requires precision measurements. Trust us, you will spend more time chasing gear patters and oil leaks if questionable parts are assembled. A call to Randy’s Ring and Pinion was made to receive a new “carrier installation kit” for around $140, which included new shims and quality Timken bearings.
So, with a less than optimal starting point and fresh parts on hand, we went into the shop on a mission to get a butt out of a sling and back into the dirt. Follow us along here and see what tools and methods we used to get this poor Dana axle back under our buddies’ truck.
Randy’s Ring and Pinion - https://www.randysworldwide.com/
Eaton Detroit Locker - https://www.eaton.com/
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Bryan Irons
Our housing was in good shape, but we had no clue where or how many shims were needed to not only set the carrier bearing preload, but also the backlash distance between the ring and pinion gears. This shouldn’t need to be stated, but DO NOT mix and match ring and pinion gears. If you do, you will be able to count the self-destruct sequence time down to the meters (not miles!)
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Bryan Irons
Every Truetrac we have run to date has been a smooth installation due to the tight specifications and top-notch quality control at the factory.
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Bryan Irons
Typical and annoying Dana design dictates that carrier bearing shims be placed under the pressed-on bearings. Without a special bearing puller to prevent damaging the bearings while pulling them on and off, we have found that buying a second set of bearings and using a flap wheel to open them up for a slip fit is the best way to complete the setup of the axle. Don’t use the old bearings and hone them, go buy a new set – and thank us later.
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Bryan Irons
With the setup bearings made, we installed them without any shims and placed the carrier into the housing. Omit the ring gear for now, too.
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Bryan Irons
Place the carrier caps in their proper locations (as can be seen with the “B” stamps aligning seen here), and tighten them to only a few ft-lbs. as we need the bearing races to be able to slide a little.
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Bryan Irons
With a dial indicator and screwdriver, pry the carrier back and forth reading the total distance traveled. This will be your total shim pack thickness AT ZERO PRELOAD. This will be important later on.
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Bryan Irons
With your total pack thickness measured, you now need to make up this thickness in shims from the included kit. This Mitutoyo micrometer we use is extremely accurate, but not completely necessary as a set of calipers can be used to get the job done. We like to place the carrier back in the housing with all the shims under one side just to make sure we have a snug fit.
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Bryan Irons
This is also time to mount the ring gear to the carrier. Use a file or stone to knock any burrs down before bolting it up.
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Bryan Irons
Some ring gears are a slight press fit onto the carriers. If this is the case, heat up the ring gear in an oven for a good 30 mins to get it to expand. Avoid the temptation to draw the ring onto the carrier with the bolts. Make sure to use a good thread-locking compound on the bolts.
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Bryan Irons
With everything bolted up (and back to room temperature) place the carrier assembly back into the axle with half the shims selected under one bearing, and the other half under the other. Tighten the bolt to the factory torque setting and measure the backlash as shown. Cross reference them with the factory allowance, or if you started with a complete housing, measure the backlash before taking the axle apart. Move the shims from one side of the axle to the other until you are within spec.
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Bryan Irons
Once happy, it’s time to remove the setup bearings and install the proper ones. Before placing the shims under the new bearings, make sure to add .005” to .007” of shims to each shim pack to add preload on the bearings. This is very important as if there is no preload, the bearings will be destroyed very quickly from rattling around. There are multiple ways to press bearings on, but a hammer is NOT one of them. A local shop can even be called upon to press them on.
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Bryan Irons
The carrier should be more difficult to get into the housing now with the preload on the bearings. Nothing a soft mallet cannot handle. If you find the carrier “dropping” into the housing or having to use excessive force to get it place into the housing, it’s time to take a step back and rethink your measurements.