Best RCAWD TRX4M Upgrades — Portal Axles, Brushless, Shocks & Steering
The Traxxas TRX-4M becomes much easier to upgrade when every part is chosen to solve a specific problem. RCAWD's current TRX4M range covers drivetrain, portal axles, suspension, steering, brass weight, bearings and driveline components, making it possible to build anything from a controlled technical crawler to a faster trail-oriented truck without treating every metal part as an automatic improvement.
The strongest upgrade path starts by deciding what the truck actually needs. More torque requires a different solution from more ground clearance. Steering precision is a different problem from suspension control, and additional brass weight should be placed deliberately rather than simply added wherever a replacement part exists.
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Best RCAWD TRX4M Upgrades — Quick Buying Guide
| Upgrade | Main Purpose | Best Fit |
|---|---|---|
| 10mm Widened Differential Portal Axle Assembly Set | 20mm total wider track, portal architecture and selectable diff setup | Technical crawler builds where axle architecture and stance are major project decisions |
| 24.4:1 High-Torque Brushless Motor Transmission | Low-speed-oriented brushless drivetrain | Crawler builds where reduction, torque and controlled wheel speed lead the brief |
| 16.6:1 Brushless Motor Transmission | Mixed crawling and trail gearing | Builders wanting brushless power without specialising entirely around low-speed crawling |
| 2-Speed Brushless Motor Transmission | Low and high gear in one brushless drivetrain | Trail-and-crawl builds using a compatible 3-channel radio system |
| 180 Motor with Metal Transmission | Brushed motor and all-metal transmission route | Builders wanting mechanical drivetrain changes without moving directly to brushless |
| Oil-Filled Front & Rear Shock Set | Suspension damping and spring tuning | Builds where suspension control needs more adjustment |
| Brass High-Clearance Links Set | Link clearance plus low-mounted weight | Bronco and Defender builds where lower-link clearance is a real limitation |
| Brass RC Steering Complete Set | Steering hardware and front-end mass | Crawler builds where steering hardware and weight placement are being developed together |
| 25T Servo with Aluminium Servo Arm | Steering actuation | RCAWD TRX4M Differential Axle builds specifically |
| #45 Steel Axles Driveshaft | Driveline durability | Modified drivetrains putting more load through the axle shafts |
| Full Bearings Set | Drivetrain service and refresh | Rebuilds where bearings are already being accessed or replaced |
| 24T / 12T Portal Axle Helical Gears Set | Portal axle internal gearing | Original TRX4M portal-axle applications requiring stronger replacement gearing |
What Should You Upgrade First on a TRX-4M?
The first upgrade should solve the first limitation you can actually identify.
If the truck becomes unstable on side slopes, widening the stance may be more useful than changing the motor. If the chassis repeatedly catches on breakover points, links and axle clearance deserve attention. If suspension movement is uncontrolled, shocks come before additional brass. If the drivetrain is already becoming the limiting factor, transmission and shaft upgrades make more sense.
This order matters because many TRX-4M upgrades interact with one another.
A wider axle changes track width. Extended hexes change the wheel position again. Brass adds mass. Different links alter geometry. Longer shocks change ride height and driveshaft angles. A more powerful motor can expose the next weak point in the drivetrain.
The best crawler therefore comes from a sequence, not from installing the largest number of metal components.
For the broader platform logic, see Best TRX4M Upgrades That Actually Improve Performance.
1. RCAWD Portal Axles — The Biggest Chassis-Level Decision
The RCAWD TRX4M 10mm Widened Differential Portal Axle Assembly Set with Diff Locker is not a cosmetic upgrade. It changes one of the core mechanical foundations of the truck.
RCAWD specifies a 10mm increase on each side, creating a 20mm total increase in track width. The set also includes two gear differentials and two diff lockers, allowing the differential configuration to be changed according to the intended terrain.
That additional width can improve lateral stability and creates more room for larger tyres, but it also needs to be considered before choosing wheel offset, extended hexes or other widening components.
RCAWD also offers the TRX4M Widen 10mm Differential Portal Axles Complete Set, another complete portal route that combines widening with metal axle hardware.
Best for: technical builds where axle architecture, stance and clearance are central to the project.
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2. Brushless Gearboxes — Choose the Ratio Before the Motor
RCAWD currently offers several TRX4M motor-and-transmission routes, and this is where choosing by purpose becomes particularly important.
The current brushless systems are offered around 2204 2800KV and 3500KV motor choices. RCAWD also states that the 24.4:1 and 16.6:1 brushless systems must be operated with a 30A brushless ESC rather than the original brushed electronics. Check the selected product variant carefully to confirm exactly which motor and ESC components are included.
24.4:1 High-Torque Brushless Transmission
The RCAWD TRX4M 24.4:1 High-Torque Brushless Motor Transmission Gearbox is the crawler-led choice in the range.
The 24.4:1 reduction is deliberately geared towards lower wheel speed and stronger reduction. RCAWD describes it as an underdrive configuration relative to the stock gearing, which makes its purpose clear: technical crawling rather than simply increasing speed.
This is therefore the brushless route to investigate when controlled movement on steep and broken terrain matters more than maximum trail pace.
16.6:1 Brushless Transmission
The RCAWD TRX4M 16.6:1 Brushless Motor Transmission Gearbox changes that balance.
RCAWD positions the 16.6:1 configuration as a compromise between usable torque and additional maximum speed, making it more appropriate for a truck expected to cover both obstacles and faster connecting terrain.
Again, the selected motor and ESC option matters. RCAWD currently lists 2800KV and 3500KV motor choices and states that a 30A brushless ESC is required.
Two-Speed Brushless Transmission
The RCAWD TRX4M 2-Speed Brushless Motor Transmission Gearbox is the most flexible drivetrain concept in the current RCAWD TRX4M range.
The low gear is intended for torque and technical running, while the high gear gives the truck a faster mode for flatter trail sections.
There is one important requirement: RCAWD states that the two-speed system is designed to operate exclusively with a compatible 3-channel transmitter. If the truck is still running a radio system without an available third channel, that needs to be solved as part of the conversion.
This is therefore the most logical drivetrain route for a builder who genuinely wants one TRX-4M to perform two different jobs rather than optimising it entirely around one fixed gear ratio.
3. Brushed Power Still Makes Sense — 180 Motor with Metal Transmission
Brushless is not mandatory simply because the catalogue offers it.
The RCAWD TRX4M 180 Motor with Metal Transmission combines a brushed 32T 180 motor with an aluminium transmission housing and metal internal gears.
RCAWD currently offers the transmission in two gearing routes: 16.6:1 and 9.77:1. That means the purchase is not simply brushed versus brushless; the gearing choice still determines how the truck behaves.
The 16.6:1 version retains more reduction, while the 9.77:1 option pushes further towards wheel speed.
This route is particularly logical when the builder wants stronger mechanical transmission hardware and a different speed character without redesigning the truck around a complete brushless electronics package.
4. Suspension — Shocks Before Decorative Metal
Suspension upgrades are most useful when they change control, travel or setup rather than simply replacing plastic with aluminium.
The RCAWD TRX4M Oil-Filled Front & Rear Shock Absorber Set with Replacement Springs provides 53mm and 59mm shock routes alongside multiple replacement springs.
That gives the builder more scope to tune ride height, damping and spring response rather than treating shock length as the only specification that matters.
RCAWD also lists a 50mm Oil-Filled Shock Absorber Set with Replacement Springs, as well as a Shock Absorber & Shock Flex Blades Set.
The correct length depends on the geometry already fitted to the truck. Longer travel is useful only when links, driveshaft angles, tyre clearance and body clearance allow the suspension to use it.
5. Steering — Upgrade the System, Not Just One Part
Steering is another area where individually attractive upgrades need to be considered together.
The RCAWD TRX4M Brass RC Steering Complete Set combines replacement steering hardware with additional front-end mass.
The RCAWD TRX4M 25T Servo with Aluminium Servo Arm provides a matching steering-actuation option, but there is an important compatibility limitation: RCAWD currently states that this servo fits the RCAWD TRX4M Differential Axle only.
The RCAWD TRX4M Servo Links & Servo Arm gives another mechanical route into the steering system.
Servo spline, axle architecture, steering links and mounting therefore need to be checked together. Do not assume that every steering component is interchangeable between the stock axle and every aftermarket axle configuration.
6. Brass Weight — Put It Where It Solves a Problem
Brass can help a crawler by moving mass lower in the chassis, but weight is not automatically beneficial simply because it is made from brass.
The RCAWD TRX4M 132g Front & Rear Portal Axle Brass Counterweight Set represents a substantial low-mounted weight change and should therefore be treated as a tuning decision rather than an automatic first upgrade.
The Brass High-Clearance Links Set combines two objectives: improved lower-link clearance and additional low-mounted mass.
RCAWD currently lists this particular high-clearance link set for the TRX-4M Bronco 97074-1 and Defender 97054-1, so High Trail or other configurations should not be assumed compatible without checking the current product page.
The Brass Steering Links & Brass Diff Cover provides another route to concentrating weight around the axle and steering area.
These parts make most sense when the builder already knows where the truck needs weight. Adding every brass option simultaneously can make it difficult to understand which change actually improved — or harmed — the vehicle.
7. High-Clearance Links — Geometry Before Appearance
High-clearance links are easy to recognise visually, but their main purpose is geometric.
The RCAWD TRX4M Brass High-Clearance Links Set is designed to improve chassis ground clearance around the lower links while simultaneously replacing lighter stock material with brass.
That makes it particularly relevant when the truck repeatedly catches its lower links on rocks or sharp breakover transitions.
If the stock link geometry is not actually causing a problem, however, this upgrade can wait. A good crawler build is often easier to tune when the driver changes one limitation at a time.
8. Driveshafts, Bearings and Gears — The Reliability Path
Not every upgrade needs to change the truck's appearance or crawling geometry.
Once power, vehicle mass and tyre grip increase, driveline components deserve more attention.
The RCAWD TRX4M Center Driveshaft Set addresses the central driveline.
The RCAWD TRX4M #45 Steel Axles Driveshaft targets the axle-side drivetrain.
The RCAWD Full Bearings Set makes most sense during a planned rebuild or when the truck is already being dismantled far enough to service the rotating hardware.
For portal-equipped builds, the 24T / 12T Portal Axle Helical Gears Set uses #45 steel helical gearing and is listed by RCAWD for the original TRX4M portal axle.
This category becomes particularly relevant after power and grip upgrades. More available torque only helps if the rest of the drivetrain can transmit it consistently.
9. Brass Wheel Hexes — Small Part, Big Geometry Consequences
Wheel hexes look simple, but changing their dimensions can affect stance, scrub radius, tyre clearance and overall track width.
The RCAWD TRX4M Brass Wheel Hex H7 × 10mm Extend Width is a deliberate widening component. RCAWD specifies a 6mm width extension and an 11g set weight for this version.
The RCAWD TRX4M 7mm Brass Wheel Hex provides another fitment route.
These should be chosen after the axle width and wheel offset are understood. Combining 20mm-total widened portal axles, extended hexes and aggressive wheel offset without planning can create far more track width than the original build intended.
Three RCAWD TRX4M Build Paths That Make Sense
| Build Direction | Start With | Add Next |
|---|---|---|
| Technical Crawler | 24.4:1 Brushless Transmission | Widened Portal Axles, compatible link geometry and suspension tuning |
| Trail + Crawl All-Rounder | 2-Speed Brushless Transmission | 3-channel radio, oil-filled shocks, steering and driveline tuning as required |
| Durability-Focused Rebuild | 180 Motor & Metal Transmission | Steel Axle Driveshafts, bearing set, portal gears where applicable |
What I Would Not Upgrade All at Once
A complete metal build may look impressive, but it can make tuning harder.
I would avoid combining widened axles, extended wheel hexes, every available brass component, longer shocks and a major drivetrain change in one step unless the final geometry has already been planned.
That approach changes track width, total mass, weight distribution, suspension behaviour and drivetrain load simultaneously. If the crawler becomes better, it is difficult to know why. If it becomes worse, the same problem applies.
A cleaner upgrade sequence is:
- identify the current limitation;
- change the component directly responsible;
- drive the truck again;
- observe the new limitation;
- then choose the next upgrade.
This keeps the build understandable and usually produces a more coherent crawler.
RCAWD as a System Upgrade Route
RCAWD's TRX4M catalogue is particularly useful when the aim is to develop specific mechanical systems: transmission, portal axles, steering, suspension, links and driveline hardware.
That allows the stock TRX-4M to remain the foundation while individual systems are changed only where the build requires them.
This is different from replacing an entire chassis architecture in one step, and it can be particularly effective when the builder already likes the stock body and basic platform but wants to develop its mechanical behaviour progressively.
For the broader decision process, our Best TRX4M Upgrades That Actually Improve Performance explains which upgrade areas normally deserve attention first.
Which RCAWD TRX4M Upgrades Should You Buy First?
If the truck is primarily a technical crawler, I would start with the axle, gearing and suspension decisions before adding cosmetic metal.
If slow-speed control and reduction are the priority, the 24.4:1 Brushless Transmission is the most crawler-focused brushless drivetrain route to investigate.
If the truck needs to cover both obstacles and faster trails, the 2-Speed Brushless Transmission offers the more flexible concept, provided the build also has a compatible 3-channel radio.
If stance and axle architecture are the priority, start with the 10mm-per-side Widened Differential Portal Axle Assembly Set before choosing wheel hexes and other widening components.
If the stock suspension is the limitation, start with the Oil-Filled Shock Set and tune the truck before adding unnecessary weight.
And if the drivetrain is being rebuilt for durability, the transmission, steel shafts, bearings and portal gears form a far more coherent package than changing unrelated cosmetic parts.
Final Thoughts
The strongest RCAWD TRX4M build is not the one with the most RCAWD parts.
It is the one where every upgrade supports the same goal.
The 24.4:1 brushless transmission makes sense for a crawler-led build. The 16.6:1 system offers a more mixed crawling and trail direction. The two-speed brushless gearbox makes sense when one truck genuinely needs two different driving personalities.
Widened portal axles can fundamentally change stance and clearance, while oil-filled shocks, links and steering hardware allow the suspension and front end to be developed around that foundation.
Brass deserves particular restraint. Use it where lower weight placement solves a real balance problem, not simply because a metal replacement exists.
And once power, grip and vehicle mass increase, remember the less glamorous parts: shafts, bearings and internal gears are what allow the rest of the build to keep working together.
Choose the problem first. Then choose the RCAWD part that solves it.
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Further Reading
- Best TRX4M Upgrades That Actually Improve Performance
- Real Scale Dynamics — RC Crawler Upgrades for Performance, Looks, Weight Balance and Realism
- BATRAZZI RC Crawler Wheels & Tyres Guide
Image Credit: RCAWD.
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Editorial Note: This is an independent product-range and upgrade-path guide rather than a hands-on review. The focus is on choosing RCAWD TRX4M components by function, compatibility and build direction rather than treating every available replacement part as a necessary upgrade.
Accuracy Disclaimer: This article is based on manufacturer and retailer information available at the time of writing. Specifications, compatibility, variants and product details may change. Always verify current information and exact TRX-4M fitment with the manufacturer or retailer before purchase.
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