Rock Crawling Adventures

A Father-Son RC Project

Authors

Andrew Dunn

Alasdair Dunn

Atticus Dunn

Published

February 4, 2026

Introduction

Platform: Traxxas TRX-4M (97054-1) → Injora BUG18 Beetle

Welcome to our upgrade roadmap for turning a stock TRX-4M into a serious rock crawling rig. This guide documents a father-son project designed around learning together, building skills, and having fun along the way.

Why This Project

Alasdair and Atticus have always been fascinated by vehicles—not just playing with them, but understanding how they work. We wanted a low-cost way to take things apart and put them back together, learning mechanical skills along the way.

The TRX-4M is small enough to work on at a desk, but complex enough to teach real concepts: suspension geometry, gear ratios, center of gravity, electronics.

The Traxxas TRX-4M turned out to be the perfect platform:

  • Strong aftermarket support with multiple manufacturers making high-quality upgrade parts
  • Modular design that’s meant to be disassembled and modified
  • Active community with plenty of guides, videos, and forums
  • Reasonable scale for young kids to handle and help work on

The Journey

The upgrades are organized into seven epochs—each a distinct build session with its own theme, parts list, and milestone. The progression is intentional: we start with the foundation (chassis, suspension, bearings), add capability (electronics, wheels), then tune for performance (gears, weights).

Primary Use: Indoor/backyard crawling with rock park visits

NoteEarly Brushless

We moved the brushless upgrade from Epoch 7 to Epoch 2—and went with the premium Roverin M30 G2 FOC sensored system for the best possible low-speed control. Epoch 7 is now marked as “Completed Early.”

Summary: The Complete Journey

Table 1: Upgrade roadmap summary
Epoch Name Focus Cost Cumulative
1 Big Build Day BUG18 Body + Chassis ~$143 ~$143
2 New Brain Day Electronics (Brushless) ~$190 ~$333
3 Big Wheels Day Lift + Tires $63-85 $396-418
4 Rescue Rig Day Winch + Lights $44-50 $440-468
5 Rock Ready Performance $40-45 $480-513
6 Heavy Metal Brass Weights $60-90 $540-603
7 Lightning Upgrade Brushless — Completed in Epoch 2

Epochs 1-2 (Running & Driving): ~$333 Epochs 1-5 (Fully Capable): ~$480-513 All Epochs (1-6): ~$540-603

What the Crawler Has After Epochs 1-2

  • New beetle body (Alasdair’s choice)
  • LCG aluminum chassis with multiple shock mount points
  • FOC sensored brushless power—the best low-speed control available for micro crawlers
  • 40.3:1 underdrive gearing—59% slower than stock for maximum crawl control
  • IP67 waterproof electronics—can handle Michigan snow and puddles
  • 200% drag brake—controlled descents, no runaway truck
  • Bluetooth app tuning—adjust parameters without programming cards
  • 6-channel radio with speed limiting for safe toddler driving
  • Brass weight at lowest points (shock ends)
  • Sealed bearings throughout

How to Use This Guide

Each epoch chapter includes:

  • Overview of what you’re doing and why
  • Bill of Materials with part numbers, links, and costs
  • Q&A answering common questions for that epoch
  • Resources with video guides and community discussions

The reference section at the end covers electronics deep-dives, parts sourcing, and compatibility notes.

Local Places

Community Resources

The TRX-4M has an active online community. These are good places to find build inspiration, troubleshooting help, and upgrade discussions.

Reddit

  • r/rccars — General RC community; good for broad questions
  • r/crawling — Dedicated to rock crawling; more focused discussions
  • r/SCX24 — Axial’s 1/24 scale competitor; similar scale, many overlapping techniques

Tip: Search “TRX-4M” within these subreddits for platform-specific posts.

YouTube Channels

These channels regularly cover TRX-4M builds and upgrades:

Forums

Last updated: February 2026