Buying guides
Traxxas TRX-4 upgrades.
The right mods, in the right order, at verified prices.
The TRX-4 is the most feature-loaded trail truck in the hobby — portal axles, a two-speed transmission, and remote-locking differentials, all standard. Our first upgrades guide covers the shared SCX10 and TRX-4 basics; this guide is the TRX-4-only deep dive: the portal-brass system that is this platform's signature mod, the overdrive gear swap, the wheelbase trap that catches parts orders (313mm vs 324mm), and the stock features you should protect instead of replacing. Every price is pulled from our live catalog.
Before you order anything: know your wheelbase
The TRX-4 family runs two wheelbases. Short-wheelbase trucks (the Sport and most 312–313mm variants) and long-wheelbase trucks (324mm — Defender and the longer Bronco and Blazer bodies) take different links, driveshaft lengths, and chassis kits. Tires, wheels, servos, and portal parts are shared across the family; anything with a length in its name is not. Check your truck's wheelbase before ordering links or a chassis — it is the most common TRX-4 parts mistake, and the easiest to avoid.
Stage 1: tires and beadlock wheels
The stock tires are a durable all-rounder tread, which is another way of saying they are not great at anything. A soft-compound 1.9-inch tire is the single biggest capability gain available, and a true beadlock wheel keeps the bead clamped when a heavy truck leans on a sidewall at full lock.
MEUS Racing 1.9-inch MS6 Super Bouncer Tires with Silicone Inserts — $45.99
The performance pick: super-soft MS6 rubber with silicone inserts included, and a fitment list that names the TRX4 outright alongside the SCX10 and Capra. The inserts are half the upgrade — they let the tread wrap rock instead of bouncing off it.
INJORA Cling On 1.9-inch S5 Tires, 120mm (set of 4) — $29.99
The value pick: INJORA's S5 super-soft, sticky compound at 120mm tall, with foam inserts in the box. Sixteen dollars less than the MS6 set, and the tire most budget TRX-4 builds end up on.
TREAL 1.9-inch Aluminum Beadlock Wheels (set of 4) — $42.98
CNC aluminum beadlocks whose fitment names the TRX-4 directly. A full set of four in one box — no pair math, no mismatched second order.
SSD RC 1.9-inch Steel Beadlock Wheels (pair) — $24.99
The steel alternative: stamped-steel looks with machined aluminum 12mm hubs, sold in pairs — budget $49.98 to do the whole truck. Steel wheels add a little unsprung weight of their own, which stage three will teach you to appreciate.
The full field lives on our crawler tires page, and every TRX-4-fit part is gathered on the TRX-4 parts page.
Stage 2: a steering servo with real torque
One servo to upgrade — and two you should leave alone.
The TRX-4's steering servo is its most-replaced part, and sticky tires plus brass will finish a tired one off. It takes a standard-size servo, and the budget end of the catalog is unusually strong right now. The shift servo and the two locker servos are a different story: they are small, specific, and working fine — leave them stock.
GXservo DS3235MG 35KG Digital Servo — $15.49
Thirty-five kilograms of metal-gear torque, down from $23.24 at Banggood. The cheapest legitimate steering fix for any 1/10 crawler, and the servo our SCX10 guide builds around too.
GXservo QY3240MG 40KG Digital Servo — $16.49
One dollar more buys 40KG and a listing that names SCX10 and TRX4 fitment outright, down from $24.74. Our pick for TRX-4 builds that plan on portal brass and tall tires.
Set your steering endpoints after the swap — a stronger servo driving into the stops is just a faster way to strip gears. The whole field is ranked in our best crawler servo guide.
Stage 3: brass at the portals — the TRX-4's signature mod
Portal axles are the TRX-4's superpower and its temptation: the portal housings sit at the lowest, widest point of the truck, which makes them the perfect place to hang weight. Brass portal parts lower the center of gravity without a single gram up high, and the catalog's range runs from pocket money to maximum effort. Front axle first — it helps climbs most — then match the rear.
INJORA 41g Brass Portal Housings (pair) — $14.99
The entry step: 41 grams per piece in a direct replacement for the stock plastic outer portal housings, front or rear fit. Two pairs ($29.98) weights both axles for less than most single upgrades cost.
INJORA 49g Brass Portal Housings (pair) — $17.99
The middle step: 49 grams per piece in a black-coated finish. Three dollars a pair over the 41g version buys about twenty percent more of the thing you came for.
INJORA 104g Black Brass Outer Portal Housings (each) — $22.99
The maximum step: 104 grams per piece, the heaviest portal housing in our catalog. Sold per piece, so a full truck is a real commitment — this is the comp-leaning end of the range, and the truck will feel it on sidehills.
Hot Racing 78g Brass Differential Cover — $38.88
Weight at the other low point: a 78-gram brass diff cover that armors the differential while it anchors it. Pairs naturally with whichever portal housings you choose.
INJORA Heavy Brass 12mm Wheel Hex Extenders — $7.99
The taster: brass hex extenders in 5, 8.5, or 10mm widths that widen the track slightly while they add wheel-end weight. Not a substitute for portal housings — see the lowest-cost sheet — but eight dollars of honest progress.
The full weight bench is on our brass and weights page, and the physics is in our weight balance guide.
Stage 4: overdrive and drivetrain insurance
Overdrive is the TRX-4 mod that changes how the truck climbs, not just how it sits. Speeding the front axle relative to the rear makes the front tires pull the truck up and over ledges. It is an inside-the-axle job — pair it with the stage-three brass work on the same axle and you only open each differential once.
Treal TRX-4 Overdrive Ring and Pinion Gears 13T/33T — $26.98
Machined overdrive gears for the TRX-4 differential. The whole stage in one part — install in the front axle and feel the difference on the first steep face.
MEUS Racing Internal Spline Universal Drive Shaft — $11.99
A steel universal shaft listed for the SCX10 and TRX4 — the drivetrain insurance policy once grip and weight go up. Match the length to your wheelbase before ordering.
INJORA Metal CVD Drive Shafts for TRX-4 (2) — $16.99
The TRX-4-specific alternative: metal CVD shafts sold for this platform in a pack of two. Same job as the MEUS shaft — pick by wheelbase and availability.
New to the concept? Our overdrive guide explains how much to run and why.
Stage 5: shocks — an honest optional
Unlike most RTRs, the TRX-4's stock GTS shocks are genuinely good — this stage is a tuning choice, not a rescue. Go here if you want dual-rate springs for a heavier built truck, or if your stock shocks are tired. Ninety millimeters is the TRX-4's stock length; stay there unless you are deliberately changing ride height.
INJORA DRX Dual-Rate Spring Oil Shocks, 90mm (set of 4) — $25.99
Dual-rate springs and X-ring seals in a full set of four, ordered in the 90mm length for TRX-4 fitment. The value way to experiment with spring rates on a brass-heavy build.
Traxxas 8260X GTS Shocks, PTFE-Coated Aluminum (pair) — $49.95
The factory upgrade: Traxxas's own PTFE-coated aluminum GTS shocks with TiN shafts, 90mm, sold in pairs. The pick if you want the stock design at its best rather than a different design.
Stage 6: power — brushed torque or Fusion control
The stock Titan motor is torquey and honest, so power comes late in the order. Stay brushed for cheap grunt, or go Fusion for the near-silent, inch-at-a-time FOC throttle control that makes a heavy TRX-4 feel surgical on rock. One caution: the two-speed transmission stays either way — both routes keep it.
MEUS Racing 540 Brushed Motor 27T — $14.99
A 540 brushed motor sold for the SCX10 and TRX4 — a fresher, torquier drop-in for a tired stock motor at a throwaway price.
Hobbywing QuicRun Fusion SE 1200KV 2-in-1 FOC System — $82.98
The value brushless route: motor and ESC in one unit, FOC low-speed control, and one less component to package. The $82.98 is the landed total at AMain — $79.99 plus $2.99 shipping.
Hobbywing QuicRun Fusion Pro 2300KV 2-in-1 FOC System — $139.99
The flagship: more power, more tuning depth, and the system most built TRX-4s end up running. Buy it once, after the truck underneath deserves it.
The wider field is compared in our best brushless crawler motor guide.
Stage 7: winch, lights, and the chassis endgame
MEUS Racing Metal Winch with Controller — $39.99
A metal winch with controller, listed for the SCX10, TRX4, and Gen8 class of trucks. On a trail truck a winch is not jewelry — it is the recovery tool that gets a heavy rig out of the hole it dug.
14LED Light Kit for TRX4 — $19.99
A fourteen-LED lighting kit grouped for the TRX4. Evening trail runs are the TRX-4's natural habitat, and lights are the cheapest way to extend the day.
INJORA LCG Carbon Fiber Chassis Kit, 313/324mm — $65.99
The endgame: carbon LCG rails that reorganize the whole truck — and one of the few chassis kits that covers both TRX-4 wheelbases in a single listing. Build this when the truck has told you exactly what it wants to become.
Stock features worth protecting
The two-speed and the locking differentials
They are the reason to buy a TRX-4 over simpler trucks. Anything that removes them — a single-speed conversion, a radio without the aux channels to run the locker and shift servos — is a downgrade wearing an upgrade's clothes. Our TRX-4 vs SCX10 guide covers what they do for you on the trail.
The stock radio system
The included radio already drives the extra channels the lockers and two-speed need. Replace it only with a system that keeps those functions — our crawler radio guide flags which ones do.
The stock GTS shocks
Good enough that stage five is optional. Fresh oil and the right spring preload will carry most trucks for years.
A sample build, priced
The core build — $135.44 total
MEUS MS6 tires with inserts ($45.99) + TREAL beadlock wheels ($42.98) + GXservo QY3240MG 40KG servo ($16.49) + INJORA 41g brass portal housings on both axles (two pairs at $14.99 = $29.98). Grip, steering, and the signature portal weight, sorted in one order.
The full path — $271.39 total
Add the Treal overdrive gears ($26.98), the INJORA DRX 90mm shocks ($25.99), and the Hobbywing Fusion SE system ($82.98) to the core build. That is a genuinely different truck from stock — for roughly half the price of a second one.
Lowest Cost Build Sheet
The same stages at the floor. Two of the four core slots swap; the servo in the main sheet was already within a dollar of the cheapest legitimate option.
The core build, cheapest route — $74.46 total
JConcepts-style 1.9 tires 123x49.5mm ($21.99, in place of the MS6 set) + INJORA W1909 stamped steel beadlocks ($28.99 for four, in place of the TREAL wheels) + GXservo DS3235MG ($15.49, in place of the 40KG) + INJORA brass hex extenders ($7.99, in place of portal housings). Tires at AliExpress · Wheels at INJORA · Servo at Banggood · Hex extenders at INJORA
The swaps, honestly
The budget tires are a JConcepts-pattern set, not genuine JConcepts — good rubber for the money, a different tire. And hex extenders are a partial substitute, not an equal one: they add grams at the wheel hex, while portal housings add 41g or more per corner inside the portal itself. If one slot keeps its main-sheet part, make it the housings — two pairs at $29.98 bring this sheet to $96.45 and keep the mod that defines the platform.
TRX-4 upgrade FAQ
What is the first TRX-4 upgrade I should buy?
Tires. The TRX-4 is a capable truck held back by a compromise stock tread. A soft, sticky 1.9-inch set transforms it — the MEUS Racing MS6 Super Bouncer tires with silicone inserts ($45.99 for four) name the TRX4 in their fitment, and the INJORA Cling On 1.9 ($29.99) is the value alternative. Everything else in this guide works better once the tires hook up.
How much brass should I put on my TRX-4?
Start at the portals, front axle first. INJORA's 41g brass portal housings ($14.99 per pair) are the entry step; the range runs to 104g-per-piece housings ($22.99 each) for maximum low weight. Portal brass is the TRX-4's signature upgrade because the weight lands at the lowest, widest point of the truck — it calms the top-heavy feel without raising the center of gravity. Do the front pair first, drive it, then match the rear.
What servo does the TRX-4 need?
A standard-size steering servo — and more torque than stock. The two budget standouts in our catalog are the GXservo DS3235MG 35KG ($15.49, down from $23.24) and the GXservo QY3240MG 40KG ($16.49, down from $24.74), the latter sold specifically for SCX10 and TRX4 fitment. Keep the stock micro servos for the two-speed shift and differential lockers — those are TRX-4-specific jobs, and they are why you should not casually replace the stock radio system.
Is overdrive worth it on a TRX-4?
Yes, if you climb more than you trail. The Treal overdrive ring and pinion gear set (13T/33T, $26.98) speeds the front axle relative to the rear, so the front tires pull the truck up and over obstacles instead of the rears pushing it into them. It is a gears-out job, so do it when you are already servicing a differential — many builders pair it with the brass portal swap on the same axle.
How much does it cost to upgrade a TRX-4?
The core build in this guide — MS6 tires ($45.99), TREAL beadlock wheels ($42.98), the 40KG servo ($16.49), and brass portal housings on both axles (two pairs at $14.99, $29.98) — totals $135.44. Adding overdrive gears ($26.98), dual-rate oil shocks ($25.99), and a Hobbywing Fusion SE brushless system ($82.98) takes the full path to $271.39. Buy in stage order; every stage is a complete, satisfying stopping point.
A quick note on links
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