The TRX-4M might be the most upgraded RC truck on the market right now — and for good reason. Traxxas built a surprisingly capable 1/18-scale platform at an accessible price, and the aftermarket has absolutely exploded around it. Whether you just unboxed yours or you’ve been crawling it stock for a few months, this guide tells you exactly what to buy first, what to skip, and what a full build actually costs.
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TRX-4M Quick Specs & Versions
Before spending money on upgrades, it helps to know exactly what you’re working with. The TRX-4M runs a Titan 180 brushed motor (87-turn), shaft-driven full-time 4WD with permanently locked diffs via spools, a steel ladder frame, 4-link suspension with oil-filled shocks, and a 7.4V 750mAh 2S LiPo with USB charger — all included in the box.
One thing worth clarifying: the stock radio is a TQ 2-channel transmitter, not a TQi. That means no Traxxas Link app, no cruise control, and no diff lock switches. Those are TRX-4 (1/10) features. The TRX-4M is simpler, and for most crawling purposes, that’s fine.
| Spec | Details |
|---|---|
| Scale | 1/18 |
| Motor | Titan 180 brushed, 87T |
| Drive | Shaft-driven 4WD, locked diffs |
| Axles | Straight solid axles (portals available as upgrade) |
| Battery | 7.4V 750mAh 2S LiPo, iD connector |
| Shocks | GTM oil-filled (QC inconsistent — see below) |
| Weight | ~468–483g without battery |
| Base Price | $159.99 |
Available versions — all share the same chassis and upgrade compatibility:
- TRX-4M Land Rover Defender (#97054-1) — $159.99, 8 color options
- TRX-4M Ford Bronco (#97074-1) — $159.99, 6 color options
- TRX-4M Chevy K10 High Trail (#97064-1) — $179.99, +35% ground clearance
- TRX-4M Ford F-150 High Trail (#97044-1) — $179.99, +35% ground clearance
- TRX-4MT F-150 Monster Truck (#98044-1) — $199.95, 8 shocks, upgraded servo
- TRX-4MT Chevy K10 Monster Truck (#98064-1) — $199.95, same platform
The High Trail and MT editions are worth the $20–$40 premium if you plan to crawl outdoors on real terrain. For indoor and desk crawling, the standard Bronco or Defender is perfect.
Browse the TRX-4M on Amazon to compare current pricing across versions.
Day One Upgrades — Do These Immediately
Two upgrades pay for themselves within the first few sessions. They address the TRX-4M’s most obvious stock weaknesses and cost under $60 combined.
Brass Portal Covers & Knuckles ($15–$35)
Weight is the most important variable in rock crawling, and the TRX-4M is genuinely too light out of the box at under 500 grams. The high-mounted ABS body creates a top-heavy center of gravity that causes the truck to tip over on moderate side hills and struggle for traction on loose terrain. Brass components at the axle level — the lowest point on the truck — fix both problems simultaneously.
A typical brass axle kit includes steering knuckles, C-hubs, diff covers, and a steering link. Together they add 52–68 grams exactly where you need them most. Individual pieces run $5–$15 each; complete kits from COOWOO, Linsvirgo, or Yeah Racing bundle everything for $15–$35.
For the highest quality individual pieces, INJORA and Treal Hobby are the go-to brands. The community particularly recommends brass steering knuckles (13–22g per pair) and brass diff covers (19–24g per pair) as the highest-impact individual pieces.
Adding brass portal covers to my TRX-4M was like flipping a switch. The truck that used to tip over on moderate side hills suddenly planted itself and crawled up. Weight is everything in crawling, and at 1/18 scale the TRX-4M is desperately light stock. Brass fixes that.
➡️ Shop TRX-4M brass portal covers on Amazon
➡️ Shop TRX-4M brass steering knuckles on Amazon
Bearing Kit ($8–$12)
The TRX-4M ships with plain plastic bushings at all 22 drivetrain locations — an unusual cost-cutting decision for a Traxxas product. Replacing them with sealed steel ball bearings is the cheapest meaningful upgrade on the entire platform: under $10 from INJORA or Treal, under $15 from Fast Eddy or the official Traxxas kit (#9745X at $20–$25).
The difference is immediately noticeable. The truck rolls more freely, the motor runs cooler, battery life improves, and low-speed crawling feels more precise. It takes about 30 minutes to install and requires no new parts beyond the bearing kit itself.
➡️ Shop TRX-4M bearing kit on Amazon
These two upgrades cost under $60 total and transform the TRX-4M from a capable toy into a genuine crawler. Everything after this is enhancement, not correction.
Crawling Performance Upgrades
Once the foundation is solid, these upgrades progressively unlock better capability on technical terrain.
Tires & Wheels ($20–$55)
The stock tires are permanently glued to lightweight plastic wheels with no beadlock capability — which means no tire swapping, no wheel weight, and no tuning. Upgrading to 1.0″ beadlock wheels with aftermarket soft-compound tires changes all three.
For tire compound, INJORA’s S5 Super Soft Sticky rubber is the clear community favorite. Their King Trekker (T1014, 58×24mm, ~$12–$16 for 4) is the best-selling 1/18 crawler tire on the market — excellent grip-to-durability balance, fits stock wheelbase without rubbing. The larger Swamp Claw (T1019, 64×24mm) offers maximum traction for mud but may require bumper trimming on standard-wheelbase versions.
Tire choice makes or breaks crawling performance — our RC crawler tires guide covers 1.0, 1.9, and 2.2 sizes in detail if you want to go deeper.
For wheels, the weight debate is simple: heavier wheels sit at the lowest point of the truck and directly improve stability. INJORA aluminum beadlocks (~$16–$22/set of 4) are the value pick. INJORA brass beadlocks (~42g each, $35–$45/set) or Treal brass Type C (~50g each, $50–$65/set) add up to 200g of wheel weight — effectively doubling the brass upgrade impact.
➡️ Shop TRX-4M 1.0 beadlock wheels + tires on Amazon
Servo Upgrade ($16–$35)
The stock 2065T servo has a plastic gear train — only the main gear is metal — delivering about 3.5 kg-cm of torque. It will eventually strip gears, especially after adding brass weight. This isn’t a matter of if, it’s when.
The Traxxas 2265 ($25–$35) is the easiest fix: direct drop-in, all-metal gears, aluminum case, 5.4 kg-cm (2.3× stock). Zero modifications, no new mount, works perfectly with the stock ECM. For maximum performance on a budget, the INJORA INJS2065 ($16–$28) delivers 7 kg-cm with a coreless motor and waterproof construction — but requires an INJORA servo mount (usually included in kit listings).
If the TRX-4MT’s upgraded servo intrigues you, that’s the 2065R — same form factor as stock with all-metal gears, roughly the same torque. Better durability than stock, but the 2265 at only $10 more offers twice the torque.
➡️ Shop TRX-4M servo upgrade on Amazon
Suspension Tuning
The GTM shocks that ship with the TRX-4M are theoretically oil-filled — but quality control is inconsistent enough that multiple reviewers, including The Drive, have opened brand-new shocks to find them completely dry. Before blaming handling on other factors, check whether your shocks actually have oil in them.
For crawling, you want 20–30 weight silicone shock oil: 20wt for maximum droop and articulation on technical rock gardens, 30wt for all-around trail use. Aftermarket aluminum oil-filled shocks from Treal (53mm, $20–$28) or INJORA (53mm, $18–$25) solve the QC problem entirely and add tuneable coilover adjustment. Their 59mm long-travel versions effectively raise ride height and increase suspension travel — a mild lift without a dedicated lift kit.
For springs specifically, RCAWD sells a three-hardness spring set ($15–$22) compatible with stock shocks if you want to tune damping without replacing the entire shock assembly.
➡️ Shop TRX-4M shock upgrade on Amazon
Additional Brass Weights
Beyond the axle kit, the community has identified several additional brass weight locations that further improve balance:
Brass wheel hex extensions (Treal, 10mm): 17g per piece × 4 wheels = 68g of unsprung weight addition at ~$18–$22. Brass skid plate (INJORA #4M-67, 53g): protects the transmission and adds weight low on the chassis, ~$12–$16. Brass high-clearance links (8-piece set): ~38g total at ~$15–$20.
A fully brass-out build without brass wheels adds roughly 237–253 grams. Add brass beadlock wheels and you’re looking at over 400 grams of added mass — nearly doubling the stock unloaded weight. The sweet spot most builders land at is 100–150g of brass, which transforms handling without over-weighting the motor and servo.
➡️ Shop TRX-4M brass diff covers on Amazon
Electronics Upgrades
LED Light Kit ($20–$30)
This is the upgrade that converts skeptics. Plug in the Traxxas Pro Scale LED set and suddenly the TRX-4M has fully functional working headlights, tail lights, brake lights, and hazard flashers — all controlled automatically by the ECM-2.5 based on throttle inputs. No extra controller, no wiring complexity: one wire, done.
Each kit is body-specific: Defender (#9784), Bronco (#9783), K10 (#9883), F-150 (#9884). All run $20–$30 at retail. Traxxas also sells a roof-mounted LED light bar (#9789, ~$15–$20) that mounts directly to the roof rack accessory.
I spent a Saturday afternoon installing a roof rack, LED lights, and a mini winch on my TRX-4M. Total cost: about $35. But the result looked like a miniature version of a real overland rig. My wife — who has zero interest in RC — actually said “that’s really cool.” That’s when you know the scale details are working.
Aftermarket LED options from INJORA ($12–$18) cost less but lack the seamless plug-and-play ECM integration. For the Traxxas ecosystem, the official kits are worth the premium.
➡️ Shop TRX-4M LED light kit on Amazon
Brushless Conversion — Worth It?
Let’s be direct: a rock crawler doesn’t need high-end speed capability. The entire point of crawling is ultra-slow, ultra-controlled movement over obstacles. So why would brushless matter here?
The answer is motor cogging. Brushed motors exhibit a jerky, stepped power delivery at very low throttle percentages — exactly where you spend most of your crawling time. Brushless motors with Field-Oriented Control (FOC) eliminate cogging entirely, delivering linear, silk-smooth throttle from 0% to 100%. The improvement in precise low-speed control is genuinely impressive.
The Traxxas Brushless Power System (#6250, $119.95) is the premium plug-and-play solution: 3350Kv outrunner motor, FOC-enabled ESC, retains all three driving modes and Pro Scale lighting compatibility. For a simpler brushed upgrade, the INJORA 180 PRO 48T motor (~$15) is the most popular budget motor swap — more torque than stock, works with existing electronics.
Most TRX-4M owners don’t need brushless. Start with brass and better tires. If crawling becomes a serious hobby and the brushed motor’s low-speed behavior starts frustrating you, then invest in brushless. Jumping straight to a $120 brushless system on a first crawler is rarely the best use of the budget.
Scale Accessories — Make It Look Real
Must-Have Scale Parts
The TRX-4M’s greatest charm is its scale presence — and these accessories push it further without requiring technical skill to install.
Roof rack: Traxxas’s official Bronco rack (#9715, ~$10) is the easiest entry point. Aftermarket metal racks with climbing ladders (Levigo, ~$15–$22) add 72g of useful weight and look genuinely impressive. LED light bar (#9789, $15–$20) pairs perfectly with the roof rack. INJORA metal trailer ($35–$50, 543g) has become one of the most popular accessories in this scale — the 543 grams it adds at the rear completely changes how the rig looks and handles on flat terrain.
For recovery accessories, GLOBACT 10-piece crawler accessory sets ($10–$15) include shovels, oil drums, antennas, and recovery boards — the kind of detail that turns a toy into a display piece.
➡️ Shop TRX-4M scale accessories on Amazon
For more scale accessory ideas, check our RC crawler accessories guide.
3D Printed Parts
The TRX-4M 3D printing community is insane. Across Thingiverse, Printables, and Cults3D, hundreds of designs exist specifically for the TRX-4M — and the list grows every week.
Popular categories include interior kits (dashboards with LCD cutouts, bucket seats, roll cages visible through tinted windows), body accessories (exhaust pipes, snorkels, mudflaps, hood scoops), functional upgrades (snow tracks, working winches, trailers with real bearings), and chassis improvements (custom servo mounts, shock towers for lifted builds).
I found a full interior kit on Thingiverse, printed it for about $2 in filament, and suddenly my Bronco had seats, a dashboard, and a roll cage visible through the windows. If you have a 3D printer, the TRX-4M is the most rewarding platform to print for.
If you don’t own a printer, Etsy sellers offer printed TRX-4M parts for $5–$20 per piece. Search “TRX-4M 3D printed” and you’ll find roll cages, bumpers, roof racks, interior kits, and more.
Hard Bodies
The TRX-4M’s stock bodies are already ABS hard plastic — a genuine advantage over the soft Lexan shells used on most RC crawlers. “Hard body upgrade” in TRX-4M terms means either alternative body styles or cage/competition bodies.
The INJORA IR60 Pickup ($33.99) is the most popular aftermarket body — ABS, 78g, available in 7 colors including metallic options, includes bed rack and grille options. The MEUS Racing Ripper V2 Nylon Cage ($30–$50) uses PA66 injection-molded construction for protection during aggressive crawling. For builders who want maximum scale detail and protection, the MEUS Racing MB18 Pro ($80–$120+) combines an aluminum body with premium CNC components.
➡️ Shop TRX-4M hard body options on Amazon
Build Tiers — How Much Should You Spend?
| Build Level | Upgrades Included | Total Cost | Crawling Ability |
|---|---|---|---|
| 🟢 Essential | Brass axle kit + bearing kit | $30–$55 | Good — stock weakness corrected, noticeably better traction and stability |
| 🟡 Performance | + Beadlock wheels & soft tires + servo upgrade + aluminum shocks + LED lights + brass hex extensions | $130–$220 | Great — full crawler capability, reliable steering, proper suspension |
| 🔴 Full Scale Build | + Brushless power system + scale accessories + alternative body + portal axle kit + additional brass | $375–$625+ | Amazing — competition-ready, fully detailed overland rig |
The TRX-4M is a truck that grows with you. Start basic and add over time. Many owners in r/traxxas proudly report spending more on upgrades than the truck’s retail price — that’s not a problem, that’s the fun.
New to crawling? Our RC crawlers complete guide covers everything from choosing a truck to building a course.
TRX-4M vs Axial SCX24 — Quick Comparison
| Feature | TRX-4M (1/18) | SCX24 (1/24) |
|---|---|---|
| Scale | 1/18 | 1/24 |
| MSRP | $159.99+ | ~$129.99+ |
| Size | ~10.3–11″ long | ~8″ long |
| Weight | ~468–483g | ~250g |
| Out-of-box performance | ✅ Better | Adequate |
| Scale realism | ✅ More presence | Good |
| Pure crawling (stock) | ✅ Stronger | Limited by weight |
| Pure crawling (modified) | Strong | ✅ Worm gears hold hills |
| Aftermarket parts | Growing fast | ✅ Larger, more mature |
| Indoor/desk crawling | Good | ✅ Smaller footprint |
| Battery life | ✅ 1hr+ (750mAh LiPo) | ~30 min |
| Best For | Trail running, outdoor crawling | Desk crawling, competition |
Both are fantastic. The TRX-4M is better for outdoor trails and scale presence. The SCX24 is better for desk crawling and technical competition courses where its worm gear drivetrain provides hill-holding that the TRX-4M’s spur gear system can’t match.
Browse the Axial SCX24 on Amazon if you want to compare both before deciding. Many enthusiasts end up owning one of each.
The TRX-4M is one of our top picks in our beginner’s guide for first-time RC buyers — it genuinely covers the whole spectrum from beginner-friendly to deeply customizable.
FAQ
Q: What is the first upgrade for a TRX-4M?
Brass axle weights — specifically a combo kit with steering knuckles, C-hubs, diff covers, and a steering link. This single upgrade adds 52–68 grams of weight at the lowest possible point on the truck, dramatically improving stability, traction, and low-speed grip. Pair it immediately with a bearing kit ($8–$12) for smooth drivetrain operation. Combined cost: under $50, combined impact: transformative.
Q: How much brass weight should I add to my TRX-4M?
The community sweet spot is 100–150 grams of added brass for a well-balanced crawler. This typically means a full axle kit (52–68g) plus brass hex wheel extensions (68g) or a brass skid plate (53g). You can go heavier — a full brass-out build with brass beadlock wheels adds 400g+ — but returns diminish and the extra mass starts stressing the motor and servo. Start conservative and add based on your terrain.
Q: Are TRX-4M upgrades compatible with the TRX-4?
No — the TRX-4M (1/18 scale) and TRX-4 (1/10 scale) use entirely different hardware. No parts cross between the two platforms. The TRX-4M has its own dedicated upgrade ecosystem built around 1.0″ wheels, sub-micro servos, 180-size motors, and its specific chassis dimensions. The TRX-4 upgrades won’t fit.
Q: Can the TRX-4M handle real outdoor trails?
Yes, with caveats. The standard-wheelbase Bronco and Defender perform well on moderate outdoor terrain — dirt paths, gravel, light rock. Tall grass and deep mud are problematic due to the truck’s small size and limited ground clearance. The High Trail editions with their 40mm ground clearance and larger tires handle outdoor terrain meaningfully better. Adding brass weight and upgraded tires makes any version significantly more capable outdoors.
Q: Is the TRX-4M worth upgrading, or should I buy a TRX-4?
Both questions deserve a “yes.” The TRX-4M is absolutely worth upgrading — its aftermarket is vast, upgrade costs are low, and a $200–$300 investment turns a $160 truck into a genuinely impressive crawler. The TRX-4 (1/10) offers inherently more capability — portal axles, 2-speed transmission, TQi radio, diff locks — but at 3× the price. If you’re new to crawling, start with the TRX-4M and upgrade progressively. If you already know you want a serious trail machine and budget allows, the TRX-4 is the natural next step.
Conclusion
Brass weights and bearings are transformative. Everything else is a bonus. For under $55, you fix the TRX-4M’s two biggest stock weaknesses and end up with a truck that dramatically outperforms what you unboxed. The full upgrade path — beadlock wheels, upgraded servo, aluminum shocks, brushless power, LED lights, scale accessories — builds out one of the best project trucks in the hobby at any price point.
The TRX-4M’s real magic is that each upgrade is an event. Adding brass, swapping tires, plugging in LED lights — each one changes how the truck looks or performs in a way you can immediately feel. That’s why people spend more on upgrades than the truck itself. It’s not a problem. It’s the point.
Start with brass portal covers and knuckles — you’ll understand why within five minutes of driving.
