Traxxas Ring Differential / Pinion Gear Differential (Rear) TRX6879R

Overview

The Traxxas Ring Differential / Pinion Gear Differential (Rear) TRX6879R is a precision-engineered transmission component designed for serious RC enthusiasts who demand high performance from their Traxxas models. This is not a complete vehicle, but rather a critical upgrade or replacement part for the rear differential system on a wide range of Traxxas 4WD models, including the popular Slash 4X4, Rustler 4X4, Stampede 4X4, and numerous other brushless RC vehicles. Whether you're a competitive racer looking to fine-tune your setup, a weekend basher who wants to maximise performance, or someone undertaking maintenance on an existing RC car, this differential gear set is an essential accessory for UK RC enthusiasts.

What makes this differential truly stand out is its spiral-cut design combined with CNC machining from solid steel. Unlike cheaper straight-cut alternatives, the spiral-cut teeth are engineered to minimise backlash while maximising traction through increased surface contact area. This makes the TRX6879R ideal for high-torque, high-speed brushless applications where reliability and performance are non-negotiable. The spiral-cut design delivers smoother operation, reduced wear, and more efficient power transfer from your brushless motor to the wheels, which translates to better acceleration, more predictable handling, and longer component lifespan.

This rear differential gear set is compatible with an impressive array of Traxxas models, making it one of the most versatile transmission upgrades available for Traxxas 4WD vehicles in the UK RC market. From the legendary Slash 4X4 in all its variants (Brushless, Ultimate, VXL) to the high-performance Rustler Ultimate VXL, the powerful Ford F-150 Raptor R, the motorsport-inspired Ford Fiesta ST Rally, the XO-1 hypercar replica, and many more, this single part number opens up performance possibilities across multiple platforms.

Key Features

• Spiral-Cut Gear Design — The teeth on both the ring gear and pinion gear are machined with a precise curved profile rather than a straight cut. This spiral design minimises backlash (the gap between meshing teeth) which would otherwise cause power loss, clunking, and reduced efficiency. More importantly, it maximises the contact area between the teeth as they mesh together, which dramatically improves traction and distributes load more evenly across the gear surfaces, resulting in less wear and longer component life.
• CNC-Machined Steel Construction — Both gears are precision-machined from a single solid block of high-quality steel using computer numerical control technology. This manufacturing process ensures absolute accuracy, consistent tooth profiles, and superior material quality compared to injection-moulded plastic alternatives. Steel construction provides the durability and strength necessary for high-torque brushless applications where plastic components would simply fail.
• 37-Tooth Ring Gear and 13-Tooth Pinion Gear Combination — This specific gear ratio has been engineered by Traxxas for optimal performance in their 4WD vehicles. The ratio between these two gears determines how power is distributed and affects acceleration, top speed, and overall drivetrain efficiency. This factory-spec ratio is trusted by competitive racers and weekend bashers alike across the UK RC community.
• Reduced Backlash Technology — By cutting the teeth with a slight curve rather than straight edges, Traxxas engineers have created a differential that operates with minimal play between components. Reduced backlash means more responsive handling, tighter turning, and more efficient power delivery to the wheels, which translates to better lap times in racing or more precise control during freestyle driving.
• High-Torque and High-Speed Optimised — This differential is specifically engineered for brushless motors which deliver significantly more power than brushed alternatives. The gear set can handle the sustained high torque outputs of modern brushless systems without degradation, making it suitable for both high-acceleration runs and sustained high-speed driving. This is a genuinely performance-focused component, not a budget alternative.
• Broad Model Compatibility — The TRX6879R is compatible with an extensive range of Traxxas vehicles including Slash 4X4 variants, Rustler 4X4 variants, Stampede 4X4 variants, Ford F-150 Raptor R, Ford Fiesta ST Rally, Ford GT, Chevrolet Corvette Stingray, Toyota GR Supra GT4, Factory Five Hot Rod Coupe, Hoss 4X4 VXL, and XO-1. This broad compatibility makes it an excellent choice for shops, teams, and multi-vehicle enthusiasts who need a single part number for multiple platforms.
• Enhanced Surface Area for Improved Traction — The curved spiral design creates more surface area where the ring and pinion gears actually make contact compared to straight-cut gears of the same size. This increased contact area distributes the enormous forces generated by brushless motors more effectively, reducing stress concentration and improving overall reliability during demanding driving.

Technical Performance

The Traxxas TRX6879R represents the pinnacle of differential technology for 1/10-scale Traxxas vehicles. The precision engineering begins with the selection of material—a solid block of high-grade steel provides the hardness and strength necessary to withstand the forces generated by modern brushless motors without deformation or tooth stripping. The CNC machining process cuts both the 37-tooth ring gear and 13-tooth pinion gear with extraordinary precision, ensuring that every tooth profile is identical and properly positioned. This level of manufacturing consistency is impossible to achieve with older production methods.

The spiral-cut tooth design is where the real performance gains materialise. As the pinion gear meshes with the ring gear, the curved teeth gradually engage and disengage rather than making sudden contact like straight-cut designs. This gradual engagement dramatically reduces the shock loads transmitted through the drivetrain, which translates directly into improved reliability and reduced noise. The increased surface contact area also means that the load is distributed over more tooth material, allowing the gears to handle higher torques without deformation. For brushless RC vehicles like the Slash 4X4 and Rustler 4X4 which produce tremendous torque, this engineering advantage is absolutely critical. The spiral-cut design minimises backlash to near-zero levels, which means there is virtually no dead zone between when you input steering or throttle commands and when the vehicle responds. This responsiveness is essential for competitive racing where milliseconds matter, and also improves the overall feel and control of the vehicle during casual driving. The gear ratio of 37 to 13 has been extensively tested by Traxxas engineers on all compatible platforms to provide the optimal balance between acceleration and top speed. This ratio ensures that brushless motors can deliver their full power potential without the differential becoming a bottleneck in the drivetrain. Whether you're running a Traxxas 4-Tec 2.0 Brushless AWD, a Slash Ultimate 4X4 VXL, or any other compatible model, this differential will unlock the true performance capabilities of your brushless motor system.

What's in the Box

• 37-tooth spiral-cut ring gear (steel, CNC-machined)
• 13-tooth spiral-cut pinion gear (steel, CNC-machined)

Frequently Asked Questions

• What vehicles is the Traxxas TRX6879R compatible with? — This differential is compatible with an extensive range of Traxxas models including the Slash 4X4 (all variants including Brushless, Ultimate, and VXL versions), Rustler 4X4 (all variants), Stampede 4X4 (all variants), Ford F-150 Raptor R, Ford Fiesta ST Rally (brushless and standard), Ford GT, Chevrolet Corvette Stingray, Toyota GR Supra GT4, Factory Five Hot Rod Coupe, Hoss 4X4 VXL, and the XO-1. This broad compatibility makes it an excellent upgrade option for anyone with multiple Traxxas 4WD vehicles.
• Is this a complete differential assembly or just the gears? — The TRX6879R contains the ring and pinion gears only. It is a gearset replacement component, not a complete differential housing assembly. You will need your existing differential carrier or housing to install these gears. If your differential housing is damaged or worn, you may need to source a complete differential assembly instead.
• What is the difference between spiral-cut and straight-cut differential gears? — Spiral-cut gears feature teeth with a curved profile that mesh gradually as they engage, whereas straight-cut gears have flat, perpendicular teeth that make sudden contact. Spiral-cut designs minimise backlash (the gap between teeth), reduce noise, distribute load more evenly across the gear teeth, and improve efficiency. Straight-cut gears are simpler to manufacture but produce more shock loads, more noise, and wear faster under high-torque conditions. For brushless RC vehicles which produce significant power, spiral-cut gears are the superior choice and are absolutely recommended.
• Why would I need to upgrade or replace my differential gears? — Differential gears wear over time with use, especially under high-torque brushless motor power. Signs that your differential needs replacing include: grinding noises from the rear end, loss of traction or sudden spinning out, visible damage or chipping on the gear teeth, or simply wanting to upgrade to better-performing spiral-cut gears if your vehicle originally came with straight-cut components. Regular maintenance including differential oil changes helps extend gear life, but replacement is eventually necessary for any heavily-used RC vehicle.
• Will these gears improve my RC car's performance? — If you are upgrading from straight-cut or worn gears, then yes, you will definitely notice improvements. Spiral-cut gears deliver sharper acceleration response, better traction, smoother operation, and reduced noise. If you are replacing worn spiral-cut gears with new ones, you will restore your vehicle to like-new performance. If your vehicle already came with new spiral-cut gears in good condition, performance gains would be minimal unless the existing gears are damaged or worn.
• Are these gears suitable for brushless motors? — Absolutely. In fact, spiral-cut gears like the TRX6879R are specifically engineered for high-torque, high-speed brushless applications. Brushless motors produce substantially more power than brushed motors, generating forces that would damage cheaper gear designs. The spiral-cut design and solid steel CNC-machined construction of the TRX6879R are perfectly matched to the demands of brushless RC vehicles like the Slash 4X4 Brushless, Rustler Ultimate VXL, and Ford F-150 Raptor R.
• How difficult is it to install these gears? — Differential gear installation requires moderate mechanical skill and some specialised tools including a gear puller to remove the old gears from the differential carrier, and careful assembly to ensure proper mesh and backlash adjustment. If you are comfortable performing basic RC vehicle maintenance, you may be able to complete this job at home with proper guidance. However, if you are uncertain, many UK RC shops offer installation services, or you can send your vehicle to a local Traxxas service centre. Improper installation could result in differential damage, so take your time and follow detailed assembly instructions.
• Do I need to change my differential oil after installing new gears? — Yes, it is highly recommended to change your differential oil when installing new gears. Fresh differential oil will help the new gears run smoothly and quietly, and will remove any metal particles from the installation process. Use Traxxas-specified differential oil at the correct weight for your application (typically 50-weight for standard conditions).
• What is the gear ratio of this differential? — The TRX6879R provides a 37:13 gear ratio (37-tooth ring gear divided by 13-tooth pinion gear equals approximately 2.85). This ratio balances acceleration and top speed effectively across all compatible Traxxas 4WD models and is the factory-standard ratio for these vehicles.
• Can I use these gears as a performance upgrade even if my original gears aren't damaged? — While the primary purpose of this product is replacement and repair, if your vehicle originally came with lower-quality straight-cut gears, upgrading to these spiral-cut gears would provide performance improvements including sharper handling response and reduced noise. However, the cost-to-benefit ratio means most users install these when replacement is already necessary.

Why Buy from RC Model Shop?

RC Model Shop is a trusted UK RC retailer and authorised dealer for all the brands we stock, including Traxxas, ARRMA, Losi, FTX, Hobbywing, Spektrum and more. Based in Walsall, we have a physical store where customers are welcome to come in, view products and purchase in store. Whether you are a seasoned competitor, a weekend basher, or just discovering the world of RC for the first time, our team of experienced RC enthusiasts is here to help you find the perfect setup and provide ongoing support. Order the Traxxas Ring Differential / Pinion Gear Differential (Rear) TRX6879R today with confidence, knowing you are buying from an authorised retailer with genuine products, expert knowledge and a commitment to customer satisfaction. Shop online or visit us in Walsall — we look forward to helping you get the most out of your RC experience.