How to Build the TRX-4 Sport Kit: Part 3
Assembling the Chassis and Installing the Electronics
We're making good time on our TRX-4 Sport kit. If you're just joining us, check back for Part 1 or Part 2 to see our progress so far. Now it’s time to put the chassis together and install the electronics. If you’d like to follow along with the manual, you can view it as a PDF here.
The main chassis assembly is straightforward—just sandwich a few parts between the steel rails and bolt on the shock towers and floor pans. Note that the rear shock tower is offset toward the front of the damper crossmember, rather than mounting in line with it. It's easier to assemble one side of the chassis first. Take your time and double-check the screw sizes and positions as you go. This way if you make a wrong step, you won't need to loosen the entire chassis to move a part around. Once you've completed one side, adding the second rail takes no time at all.
Rear shock tower is offset toward the front
Adding the second rail is a snap
Here is a shot of the completed chassisNow that the chassis is complete, we need to install the transmission that we built in Part 2. The transmission keys to slots in the center skidplate and secures in place with screws that go in from the top. With the transmission in place, we can now move on to the electronics. For info about our servo, speed control, motor, and radio system choices, visit Part 1.
Drop the transmission into place
TRX-4 electronicsThe motor plate has fixed positions for the motor, so you don’t need to worry about setting gear mesh—just choose the correct holes for the pinion tooth count. The kit’s 17-tooth pinion uses the “C” holes. Refer to the manual for the correct holes for alternate gear combinations. If you don't see a gear combination listed, it probably won't fit due to clearance issues. Make sure that you align the pinion with the spur gear before installing the gear cover.
Keyed holes make setting the gear mesh simple
Use hole "C" for the stock 17-T pinion gear
Align the pinion and spur gears before installing the cover
When installing the receiver, place it in the front as shown below. This will give you more room to stow the wiring. It also aligns the receiver's set button with the opening in the box lid. We’ll divert from the manual here, because we're installing the 2262 BEC which includes a taller receiver box lid. The taller cover also includes a separate opening for the BEC plug. Now that the receiver is mounted, we can install the servo and speed control.
Mount the receiver as shown
2262 BEC kit
The BEC includes a taller lidThe 400 Red servo requires the powerful 2262 BEC in the TRX-4. It ensures the servo receives full power without dropping the receiver voltage. Install the servo so the wire exits to the left side of the chassis. The XL-5 HV mounts securely to bosses in the floor pan. Tuck the wire under the mounting tab, and route the wire as shown in the manual so it won’t get pinched under the battery tray when it’s installed later.
Servo wires exit to the left
Wiring diagram
Tuck the wire as shownThe BEC installs on top of the receiver via a pre-cut foam pad. Once that's in place it's time to mount the servos from the 8195 differential kit.
Mount the BEC on top of the receiver
Mount the differential servos in the bracketThe servos install alongside the transmission, and the wiring is a simple matter of matching the plugs to the numbered receiver ports per the instructions. Stuff the wires into the box, make sure the blue o-ring seal is in place, and then install the lid. The battery tray slots into the chassis rails and bolts to the top of the transmission. That completes the chassis build.
Plug the wires into the receiver
Caraefully seal the receiver box
Install the battery tray
Here's a look at the completed chassis with the electronics installedThat's all for part 3 of our TRX-4 Kit build. Coming Up in Part 4: shocks and axles! Missed a step? Click on the links to go back to Part 1 or Part 2.
