If your ARRMA Infraction 3S has a broken rear chassis section, you’re not alone. Chassis breakage is one of the most frustrating issues for bashers and street racers, especially as these cars hit higher speeds in 2026. This guide walks you through every step of ARRMA Infraction chassis repair for a broken rear, covering tools, parts, pro tips, and upgrade options. You’ll finish knowing exactly how to swap out the rear section and get your Infraction 3S running true again.
ARRMA Infraction 3S: Rear Chassis Weak Points and Failure Scenarios
The rear of the ARRMA Infraction 3S is susceptible to cracking or snapping at the suspension mounting points and behind the center driveshaft, especially after high-speed impacts or repeated jumps. Most failures occur on the V2 and V3 models (2023–2026), which use a 6061-T6 aluminum chassis plate, 3mm thick, measuring 550mm long and 170mm wide.
With a stock 3200Kv brushless motor and a 15T pinion, the Infraction 3S reaches up to 50mph on 3S LiPo. At those speeds, a curb hit or failed drift puts enormous leverage on the rear section. Gravel bashing and street launches also stress the aluminum around the rear gearbox housing. Over time, even small flex or micro-cracks propagate, leading to a full break or a twist that throws off alignment.
In our experience, the most common breakage is at the rearmost mounting holes, but some chassis develop hairline cracks near the rear brace or diff mounts. If you’re running big power upgrades or heavier wheels, the risk increases. Once the rear is compromised, you’ll notice the rear end sitting crooked, diff misalignment, or a drivetrain grind. Immediate repair is required to avoid further drivetrain or suspension damage.
→ ARRMA Infraction 3S, This is the most popular 1/8 on-road platform for street bashing and drifting in 2026, making repair resources and parts easy to find.
Tools, Parts, and Prep: What You Need for a Successful Chassis Swap
You’ll need a few core tools and the right replacement parts to do an ARRMA Infraction chassis repair for a broken rear. Start with a quality 2mm and 2.5mm hex driver, a good #1 Phillips, long-nose pliers, and a small hobby knife for wire management. A powered driver speeds things up but always finish bolts by hand to avoid stripping aluminum. You’ll also want blue threadlocker, isopropyl alcohol for cleaning, and a non-marring mallet for gentle persuasion during reassembly.
The main part is the replacement chassis. For the Infraction 3S V2/V3, the ARRMA ARA320563 (6061-T6) is the OEM part, weighing about 400g. Aftermarket options from GPM, Hot Racing, or Just Bash It RC use 7075-T6, which is 30% stiffer and more resistant to bending, but can transfer more shock to plastic parts. If your rear diff case or suspension hangers are damaged, buy those as well: the ARA320605 rear gearbox housing, ARA330679 suspension mount, and a fresh set of M3x10, M3x12, and M3x18 screws (ARRMA AR724505, ARAC9440 sets work).
Don’t forget to have threadlocker for metal-to-metal bolts, and dielectric grease for the diff input. For electronics, a LiPo-safe soldering iron is handy if you encounter frayed wires. Lay out your workspace with trays for screws and subassemblies. Mark screw positions on a spare body post or print a screw map if you’re new to teardown work. Finally, check your LiPo voltage before starting, especially if you plan to bench-test after the repair. A healthy 3S is 12.6V fully charged.
→ LiPo Balance Charger, Essential for keeping your 3S or 6S packs safely maintained before and after repairs.
Step-by-Step: How to Replace the Broken Rear Chassis Section
Start by disconnecting your battery and removing the body shell, wheels, and front bumper. Use your hex driver to remove the center driveshaft (two grub screws at each end), and set aside the dogbones. Next, unscrew the rear wing, diffuser, and wheelie bar if you use one. These are attached with M3x12mm and M3x18mm bolts.
Remove the rear shock tower (four 2.5mm hex screws on top), then unscrew the lower shock mounts from the arms. If you see bent hinge pins or broken rod ends, replace those now. With the rear assembly exposed, unscrew the gearbox case from the chassis (six 2.5mm hex screws underneath and two above). Carefully wiggle the rear diff housing free. Check the condition of the input bearing (usually a 10x15x4mm, ARRMA AR610005), and replace if gritty or loose.
Now, strip out the center electronics tray. Disconnect the ESC and servo leads, unscrew the receiver box, and lift out the servo. If your servo is tired or showing slop, install a metal gear upgrade while you’re in here. The
→ Metal Gear Servo, A high-torque, metal-geared servo increases steering response and holds up to hard landings, especially during and after a chassis swap.
stock ADS-15M (15kg/cm at 6V) is just adequate, but a 20kg or 25kg model transforms handling.
With the chassis bare, compare your new and old plates. If your new chassis is aftermarket, check hole alignment and countersink depthsome cheap clones need touch-up with a hand deburrer. Clean all contact areas with alcohol. Begin reassembly by reversing the teardown: seat the rear gearbox first, torque screws in a cross pattern, then reinstall the electronics tray, shocks, and drivetrain. Use blue threadlocker on all metal-to-metal screws. Don’t overtighten; the Infraction’s aluminum will strip if you overdo it. Reinstall wheels, wing, and wheelie bar. Do a bench test (no wheels) for servo centering and throttle response, then drop the car to the ground and check ride height and rear symmetry. If you see sag, tweak the shock collars or refill the shocks (stock oil: 600cSt, 70mm eye-to-eye).
Key Differences That Actually Matter: Stock vs Aftermarket Chassis, and What to Watch For
Stock ARRMA chassis use 6061-T6 aluminum, which offers a balance of bend resistance and vibration absorption for street bashing. In contrast, high-end aftermarket plates (typically 7075-T6) are both lighter and stifferby up to 30%though they cost $30–$60 more as of 2026. That stiffness can reduce flex and keep geometry intact after a hit, but it sometimes transfers force into plastic differential cases, leading to breakage elsewhere.
Aftermarket chassis often have additional bracing holes, countersunk sides for low-profile hardware, and anodized coatings for wear resistance. Some even shave a few grams (e.g., a GPM 7075 plate at 370g vs 400g stock). However, some budget replacement plates have poor tolerances: misaligned holes make gearbox and arm installation tricky, and excess burrs can cut wiring sheaths or create stress risers that cause premature cracks.
The length and thickness matter too. Infraction 3S plates are 3mm thick and 550mm long. If you try to use a Senton or Typhon 3S plate (521mm long), nothing lines up in the rear. Always check the part number: ARA320563 for Infraction 3S; don’t confuse it with ARA320517 (Typhon/Senton/Granite). Mounting hardware also differs, as Infraction’s rear requires longer M3x18mm bolts for the gearbox and M3x12mm for the wing stay, while Typhon uses shorter screws. Make sure to inspect all fasteners for threadwear and replace as needed.
Finally, if your rear break was caused by a severe impact, check the rear suspension arms, hinge pins (ARRMA AR330523), and rear hub carriers (ARA330563). A bent hinge pin or cracked hub quickly ruins new chassis work. If you’re running high-power setups (e.g., 4S conversions), use alloy rear braces and upgraded diff cases to prevent future failures. For more on chassis and drivetrain compatibility, see our Mojave/Kraton/Typhon suspension tuning article.
Side-by-Side Specs: Stock vs Aftermarket Infraction 3S Chassis
| Feature | Stock Infraction 3S (ARA320563) | 7075 Aftermarket (e.g., GPM/HR/JBI) |
|---|---|---|
| Material | 6061-T6 Aluminum | 7075-T6 Aluminum |
| Thickness | 3mm | 3mm (some 3.5mm options) |
| Length | 550mm | 550mm |
| Weight | 400g | 370g–390g |
| Anodizing | Clear/Silver | Usually Colored (Blue/Red/Black) |
| Brace/Hardware Holes | Stock locations only | May include extra holes for braces |
| Price (2026 USD) | $55–$65 | $82–$110 |
| Fit Tolerances | Factory precise | Varies by brand (GPM/HR best) |
| Flex Resistance | Moderate | High |
| Compatibility | Infraction 3S only | Infraction 3S only (sometimes Typhon/Senton 3S w/ mod) |
Real-World Performance: Testing on Asphalt, Gravel, and Backyard Bashing
After a chassis swap, testing your Infraction 3S on different surfaces reveals how the repair holds up. On smooth asphalt, a proper install keeps the car tracking straight even at full throttle (50mph+), with no weird rear wiggle or diff whine. Listen for drivetrain noise: a misaligned rear can quickly shred the plastic diff case or chew up the center driveshaft coupler.
On loose gravel, the rear end faces bigger impacts from small stones and sudden traction loss. With a stock chassis, we’ve seen microflex that sometimes leads to a rear end “walk” where the back drifts away under acceleration. Upgraded 7075 plates keep the rear rigid, but sometimes transmit more shock into the rear diff or suspension blocks, which can lead to cracks there if you’re running heavy wheels or a 4S power mod. Check hardware after your first bashing sessionloose screws here spell trouble later.
Backyard jumps and off-road launches are where chassis repairs really get tested. Even though the Infraction is designed for street, plenty of us send these cars off small ramps. If your repair is solid and the hardware torqued right, the car lands flat and doesn’t develop a rear-end squeak or bounce. If you notice new noise, recheck rear diff mounting and shock pivots.
In all cases, keeping electronics safe is crucial. After a hard impact or chassis swap, inspect servo and ESC wires for pinches or insulation cutsthese are common failure points after wrenching. For those running bigger batteries, like a 6S LiPo (though 3S is stock), watch the chassis for flex and the electronics tray for stress cracks. Using a balance charger after big runs keeps packs healthy and avoids puffing.
→ 6S LiPo Battery, For power-hungry upgrades or testing chassis strength, a 6S LiPo pushes performance and exposes any weak points in your repair or mods.
Buying Guide: Which Chassis, Parts, and Upgrades for 2026?
If you’re buying a replacement chassis in 2026, stick to known brands and always match the part number to your exact Infraction 3S model. For daily bashers or first-time repair jobs, the OEM ARRMA 6061-T6 chassis (ARA320563) is the safest bet: it fits perfectly, includes all needed holes, and costs $55–$65. For racers or those running higher power, a 7075-T6 version from GPM or Hot Racing ($82–$110) delivers stiffer handling and longer life, especially if you’ve broken multiple plates in the past.
Budget plates from eBay or AliExpress might save you $20, but we’ve seen too many with misaligned holes, poor countersinks, and soft alloys that bend fast. If you choose aftermarket, inspect machining and anodizing finish before installing. For hardware, buy a full screw kit (M3x10 to M3x18), and don’t cheap outARRMA or Tekno brand screws hold torque better than generic ones.
Upgrade while you’re inside: swap the stock servo for a high-torque metal gear version (20–25kg), and consider alloy rear braces or diff cases for added strength. For those pushing voltage (4S or 6S mods), check ESC and motor temps after the first few runs, and always run a LiPo balance charger to maintain battery health. If you’re new to RC wrenching, ARRMA’s exploded diagrams and community YouTube guides are invaluable. For more on battery and connector upgrades, see our battery compatibility guide.
Frequently Asked Questions
How do I know if my Infraction 3S chassis is really broken?
The most obvious signs are a visible crack or bend behind the rear diff, rear end sagging, or the drivetrain binding in reverse. If the rear sits uneven or the wheels toe out suddenly, inspect for hairline cracks near the gearbox mounts or mounting holes.
Can I repair a cracked chassis or do I have to replace it?
Minor cracks can sometimes be braced with an aluminum plate and M3 screws, but any full break or severe bend requires replacement. Running with a compromised chassis risks drivetrain and suspension damage, so full replacement is safer for performance and longevity.
What’s the difference between 6061 and 7075 aluminum chassis plates?
6061-T6 is softer but absorbs vibration better and is stock on the Infraction 3S. 7075-T6 is 30% stiffer and lighter, used in high-end upgrades, but can transfer more shock to plastic parts, sometimes causing diff or arm damage in big crashes or jumps.
Do I need to remove all electronics to swap chassis?
Yes, the receiver box, ESC, and servo all mount to the chassis and must be removed for a full swap. Take care not to damage wires or connectors, and use isopropyl alcohol to clean old tape residue before reinstallation for best wire management.
Which screws and hardware should I replace during a chassis repair?
Always replace any stripped or bent screws, especially M3x12mm and M3x18mm used in the rear gearbox and suspension mounts. Stock ARRMA hardware is stronger than generic screws and holds torque better, reducing future loosening or breakage.
Is it safe to run a 4S or 6S battery on a repaired Infraction 3S?
The stock Infraction 3S electronics are rated for 3S LiPo (11.1–12.6V). Running 4S or 6S requires upgraded ESC, motor, and sometimes drivetrain components. Only do this if you’ve reinforced the chassis, rear diff, and used high-torque electronics to prevent immediate breakage.
Will an upgraded metal gear servo help after a chassis repair?
Yes, a metal gear servo provides more precise steering, resists slop, and holds up better to crash impacts or rough landings. Upgrading during chassis replacement makes sense, as access to mounts is much easier when the car is fully apart.
Final Verdict: The Right Way to Repair and Future-Proof Your ARRMA Infraction 3S
Repairing a broken rear chassis on your ARRMA Infraction 3S is one of those jobs that separates casual bashers from true RC enthusiasts. If you take the time to prep thoroughly, use quality replacement parts, and upgrade weak points like the servo and hardware, your car won’t just get back on the roadit’ll run straighter, handle better, and last longer, even as the speeds and jumps get bigger in 2026.
We’ve run these cars hard on every surface imaginable: city parking lots, cracked asphalt, loose gravel, and backyard jumps. A careful chassis repair (especially with upgraded 7075 alloy) restores full alignment, virtually eliminates flex, and protects your investment from future breakage. But don’t skimp on the details: inspect every hinge pin, check the rear diff for smoothness, and always use blue threadlocker on metal-to-metal bolts. If you’re new to wrenching, ARRMA’s modular design makes the repair very manageable, as long as you stay organized with your hardware.
Don’t forget the upgrade opportunities a teardown provides. Swapping the stock servo for a high-torque metal gear unit, adding an alloy rear brace, and using a solid LiPo charger to maintain your packs all contribute to a more reliable RC experience. For most users, the stock 6061 chassis is a perfectly solid repair, but if you’re chasing high speeds, running 4S or 6S, or just want zero flex, step up to 7075. Either way, with the right approach, your Infraction 3S will be ready for anything you throw at itcurbs, jumps, or 60mph drifts included.
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