Arrma’s lineup of Boost RTR kits are some of the best beginner models we’ve seen in many years. This suite of 2WD trucks provides plenty of smiles per mile, all while staying extremely easy to drive and even easier to work on. Though the 2WD trim is a good deal of fun on its own, Arrma offers their Traction Boost upgrade set for enthusiasts looking to take the next step with their Boost truck by converting it to four-wheel drive. This traction upgrade kit comes with everything you need to convert your Boost Truck from 4×2 to 4×4. Let’s jump in and take a closer look at the installation process and our thoughts on this upgrade set.
As mentioned, Arrma includes everything you will need to convert your Boost truck from two-wheel to four-wheel drive. The kit contains a fully built front differential pre-filled with oil and pre-installed outdrives encased in an easy-to-install cage along with two outer axles and a center driveshaft. The driveshaft comes with two different lengths for the front section, the shorter being intended for the Granite and Vorteks models and the longer being intended for the Senton. All of this comes neatly packed and fitted into a clean cardboard box along with a decal sheet and matching instructions. I found the instructions to be helpful but slightly sparse in the details of certain steps, hence why I decided to write this guide.
Loosening the Front
Before starting the installation process, be sure to remove all four wheels. We may only be working on the front end, but removing both the front and back wheels will make the overall job a little bit easier. Once the wheels have been removed, it’s time to remove the screws from the lower shock mount and the upper link where it meets the steering knuckle. Completely remove these screws so the steering knuckle can dangle freely. Do this for both sides.
Replacing the Spindles
Once the knuckles can dangle freely, we need to replace the front spindles with the new outer axles. Take a set of pliers and carefully remove the wheel hex. After removing the hex, carefully remove the pin and place it aside. Do this for both sides. After applying a little bit of pressure to the spindle it should pop free from the steering knuckle.
Once the spindle has been removed, simply replace it with the new outer axle. In the instructions this was shown as a simple swap of parts, but in practice I found that the inner diameter of the inner bearing was fairly tight on the new outer axles. This is actually a good thing as it means Arrma did a good job with their design tolerances and limited the amount of slop in these crucial parts. Though this is a welcomed feature, it does make fitting the bearing slightly tricky since it can’t be easily slipped on. I was able to successfully fit the inner bearing onto the axle by first placing the bearing as snuggly as I could. I then used a pair of channel lock pliers to apply slight pressure very carefully to the bearing on either side, alternating side to side until the bearing was fully seated. To reiterate—I want to put emphasis on careful and very slight pressure; we don’t want to ruin the bearing or new axle, after all.
Once the bearing was fully seated the new axle slotted right into place within the steering knuckle. After swapping in the new outer axles, simply replace the pins, reinstall the wheel hexes, and replace the upper link and lower shock mount screws. The wheel hexes will keep the axles in place while we work on installing the differential.
When performing any kind of upgrade or maintenance work, it’s always a good idea to set parts aside in a tray or parts dish so they don’t roll off the table or get misplaced. This can be anything from an unused cup or tin to a dedicated tray just for this purpose. Recently, I’ve really enjoyed using our own RCCA-branded parts trays made by RPM.
Installing the Diff & Driveshaft
Now it’s time to install the front differential. Arrma notes the four screws that need to be removed in the instructions, all located on the bottom side of the truck. In order to loosen the diff housing, we need to remove these screws. Each one of these screws is rather long, so be sure to take care when removing them. Just take your time and be sure your hex tool is properly seated in place before loosening.
Once all four screws have been removed, we can easily pivot the diff housing up and out of the way. Doing this will reveal the placeholder that Arrma installs at the factory. Remove this placeholder and discard.
Before installing the diff, add some grease around the bevel gear, making sure to spin it as you go to apply the grease to the pinion bevel as well. The differential comes pre-built and pre-filled with oil, but some added grease on the external gears will ensure the diff has a long service life. After grease, simply place the diff into the diff housing. The diff cage drops right into place, with driveshaft spline facing inward and the flat side of the cage towards the bottom of the housing. Be sure to slot the outdrives into the outer axles as you do this and the whole thing should drop right into place. Once it’s installed, simply replace the diff cover and reinstall the diff cover screws.
After we’ve buttoned everything up, we only need to install the center driveshaft. As noted, the kit comes with two different-length front sections. If you have a Senton, use the longer piece. If you have a Granite or Vorteks, use the shorter one. Place the spring onto the tip of the front shaft and place the splines into the sleeve of the rear section. This inner spring keeps tension on the driveshaft and ensures proper performance, so don’t forget it. Install the driveshaft front-first and finish by notching the rear into place. Arrma designed this driveshaft with heavy-duty splines to keep it in place. Simply match up the splines and drop it into place.
Arrma includes a very basic set of tools with the Boost RTR kit. Although they will work for small jobs, it’s highly recommended that you have a good quality set of hex drivers when performing this upgrade and other more involved maintenance tasks. Removing the 2-inch-long diff housing screws with the tiny included L-handle hex key would be absolutely no fun, so be sure you have some quality drivers on-hand to make the work, and your life, that much easier.
Converting the truck from 2WD to 4WD provided an instant improvement in traction and handling. The beauty of the truck’s stock 2WD design is that it’s simple and easy to maintain, but after upgrading to the 4×4 setup it’s hard to imagine wanting to go back. The chassis is truly a 4×4 design and this traction upgrade set helps the truck to reach its full potential. With the added grip and improved performance, the truck brings that much more enjoyment when taking it out for bash sessions.
I hope you found this brief guide helpful. If you’re looking to get the most out of your own Arrma Boost truck, I highly recommend you consider installing one of these upgrade kits. As always, thanks for reading. I’ll catch you in the next one.
4×4 Transmission Upgrade Set: Arrma Boost
Text and Images by Lauren Short