TRUTRAC AXLE SWAP

How precision and patience can bring your rig back to life for smoother runnings on the trail.

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, which 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 snowand 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 patterns 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.

4 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.

2 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.

3 Typical and annoying Dana design dictates that carrier bearing shims be placed under the pressedon 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.

5 Place the carrier caps in their proper locations (as can be seen with the “B” stamps aligning here), and tighten them to only a few ftlbs. as we need the bearing races to be able to slide a little.

8 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.

7 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.

6 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.