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Time to wrap up our TRX-4 Sport kit build. We’ll paint the clear body, assemble and install the Expedition Rack and a bunch of detail parts, get the radio gear dialed in, and then we can drive. If you're just joining us, you can catch up by reading Part 1 or Part 2, Part 3, Part 4, and Part 5 to see how we got here. If you’d like to follow along with the manual, you can view it as a PDF here.

The TQi radio system we installed back in Part 3 is the 6507R version, which includes the 6511 Traxxas Link module, so we can program and adjust the radio system via Bluetooth and the Traxxas Link smart-device app. We’ll use the app to “tell” the receiver it’s installed in a TRX-4, and the correct settings for the T-Lock servos will be uploaded automatically.

The receiver is not assigned to a model, so the app will ask you to select the model you’ve installed the receiver into. Just swipe until you reach your model, or the one closest to the configuration you want. Since we installed T-Lock differentials in our Sport, we chose the TRX-4 Chassis Kit because it’s T-Lock equipped.

The app will ask if you want to rename the model. We switched “Chassis Kit” to “Sport.” Hit “Save,” and we’re back at the home screen. Notice that the picture in the upper left corner has changed to the TRX-4 Chassis Kit.

Verify that the T-Lock switch is properly selecting the locked and unlocked settings, and the steering is turning left and right to match wheel inputs. The transmitter’s Steering Trim knob is used to center the front wheels if they’re not quite pointing straight ahead when the wheel is at neutral. If the wheels are too far off center to correct via the trim knob, return the knob to the centered position, then remove and reinstall the truck’s servo arm as close to centered as you can. Then it’ll be close enough to fine-tune with the Steering Trim knob.

Before painting the clear body, clean the inside with warm water and dish soap to remove any mold release, dust, or finger prints that might interfere with the paint. After drying the body thoroughly, you can stick the window masks in place, inside the body. Use your thumbnail or a credit card to burnish the edges down fully and ensure a bleed-proof seal. The Sport’s polycarbonate body requires special paint, which you can find at your local hobby store. This paint bonds to the clear plastic to resist chipping or flaking when the body flexes and endures impacts.

Clear RC bodies are painted on the inside. For best results, spray two light coats to get full coverage. This is an outdoor job, of course, and if there’s a breeze, position yourself so any overspray blows away from you. It’s also smart to wear a painting mask—that goes for any spray-painting task. The Sport kit includes black decals to cover the fender flares, but instead of applying the decals, we painted them black with a neat trick. Using a fresh blade in your hobby knife, gently cut slice the overspray film along the fender line, then peel it off of the fender. Now you can brush- or spray-paint the fender, and the masking film will give you a nice, crisp line when you peel the rest of the body. We painted the bed black using the same trick as the fenders. The window masks can also be removed in this step, and you can apply the window-molding decals.

Instead of decals, the grille and tailgate are molded parts, ready to accept optional LED lights. The body is pre-cut to accept the inserts, they just plug right in. The optional 8084 LED headlight / tail light set and 8028 power supply are all you need to light up your TRX-4 Sport kit

The grille and tailgate secure from the inside of the body with screws, so there’s no tape to fuss with. Anchor points for LED wires and components are built in, making it easy to do a neat installation if you get the optional light set.

The scale accessories look great by themselves, but with just a little more work you can add some really amazing detail. All it requires is some ordinary model paint and inexpensive fine-point brushes. The fire extinguisher looks great with just a little black and silver paint for the handle and hose. The “metal” bands are chrome tape (check the RC airplane finishing section at your hobby store), and the black band was sliced from a strip of electrical tape.

The Expedition Rack is a quick build. The axe and shovel are designed to fit the rack one way, as shown. They fit onto pins so they don’t rotate in the holder. The body is pre-drilled for the Expedition Rack, and is secured from the inside with molded retainers. They side retainers are labeled RIGHT and LEFT with arrows showing which way they should face, so installation is super easy. You can also see the molded-in loops that will hold the LED wires if you install the optional light kit.

With that, the TRX-4 Sport build is complete! It’s super-satisfying to say “I built it myself,” and there’s no better way to understand and appreciate the engineering built into your machine. If you’re ready to add a TRX-4 to your RC collection (or another TRX-4, for you super-fans), and building it yourself looks like fun, go for it!