Overview
The ARRMA Pinion Gear, 25T HD Mod1 Safe-D5 is an essential replacement or upgrade component for serious RC enthusiasts running ARRMA brushless speed trucks and monster trucks across the UK. This tough steel pinion gear is precision manufactured to deliver smooth, reliable operation in extreme RC conditions, whether you're bashing at high speeds or pushing your vehicle to its limits on the track. If you own an ARRMA 1/5 or 1/7 scale brushless RC vehicle, carrying a spare pinion gear in your RC tool box is smart maintenance planning — gears are high-wear consumables that may need replacement after intense driving sessions.
Designed specifically for 5mm motor shafts, this 25-tooth Mod1 pinion gear features ARRMA's acclaimed Safe-D5 profile, which is engineered to prevent catastrophic drive loss if the set-screw ever backs out during aggressive driving. This is a genuine ARRMA part, manufactured to the same exacting standards as the original equipment supplied with ARRMA's flagship brushless trucks, including the Kraton 8S, Outcast 8S, Big Rock, Felony, Infraction and Limitless models. Whether you're a competitive racer fine-tuning your gearing ratio or a weekend basher looking for a replacement part, this pinion gear delivers the durability and precision you'd expect from ARRMA's engineering.
The combination of strong steel construction, precision-manufactured wide tooth profile, and the innovative Safe-D socket design makes this one of the most reliable pinion gears available for high-performance 1/5 and 1/7 scale RC trucks. It's the kind of component that separates reliable, trouble-free running from unexpected breakdowns mid-session.
Key Features
- Strong and durable steel construction — This pinion gear is manufactured from high-strength steel that resists wear, stripping and deformation even under the extreme stresses of brushless motor power and aggressive acceleration in 1/5 and 1/7 scale RC trucks.
- Precision-manufactured wide tooth profile — The tooth design is engineered for smooth, quiet meshing with the spur gear, reducing noise and vibration whilst maintaining consistent power transfer and improving overall drivetrain efficiency.
- Safe-D5 socket design — The distinctive D-shaped hole matches your motor's D-profile shaft, ensuring that drive and brakes are not lost if the set-screw backs out during intense driving or after impacts. This is ARRMA's answer to pinion gear failures caused by loose fasteners.
- Compatible with 5mm motor shafts — Engineered to fit standard 5mm diameter motor shafts found on ARRMA brushless motors, ensuring perfect fitment and reliability across the ARRMA brushless vehicle range.
- Precision-manufactured threaded set-screw hole — The M4 x 4mm set-screw hole is precisely threaded to prevent stripping and ensure a secure, repeatable fastening that holds even under continuous high-speed running.
- E-clip retention included — Supplied with a 3.2mm E-clip for additional motor shaft pinion retention, providing a secondary safety measure to keep the gear firmly attached to your motor shaft.
Technical Performance
This 25T Mod1 pinion gear delivers the technical excellence expected from ARRMA's precision manufacturing. The Mod1 pitch specification is standard across ARRMA's drivetrain components, ensuring perfect meshing with compatible spur gears. The 25-tooth configuration is ideal for speed-oriented setups on 1/5 and 1/7 scale brushless vehicles, offering a balance between acceleration and top-end velocity. The wide tooth profile isn't just about durability — it fundamentally improves power delivery by increasing the contact area between pinion and spur gear teeth, reducing stress concentration and minimising the likelihood of tooth stripping during aggressive acceleration. The Safe-D5 socket design is a genuine innovation in RC drivetrain safety; by locking the pinion gear to the motor shaft's D-profile, it prevents the catastrophic loss of drive that occurs when traditional round-hole set-screws back out. Steel construction ensures the gear retains its dimensional accuracy and tooth profile geometry even after hundreds of running hours, unlike inferior materials that deform under continuous high-speed stress. This is a component engineered for the demands of 8S LiPo brushless RC trucks — vehicles capable of extreme acceleration and sustained high-speed running that would quickly reveal weaknesses in inferior pinion gear designs.
What's in the Box
- 1 x 25T Mod1 Safe-D Pinion Gear (steel, precision manufactured)
- 1 x Set Screw - M4 x 4mm
- 1 x E-Clip - 3.2mm
Frequently Asked Questions
- What ARRMA RC vehicles are compatible with this 25T Mod1 pinion gear? — This gear is a standard or optional part for the 1/5 KRATON 8S, 1/5 KRATON 8S EXB, 1/5 OUTCAST 8S AVC, 1/5 OUTCAST 8S EXB, 1/7 BIG ROCK 6S, 1/7 FELONY 6S AVC, 1/7 INFRACTION 6S AVC, 1/7 LIMITLESS 6S, and various other ARRMA brushless trucks. Check your vehicle's parts manual to confirm fitment for your specific model and year.
- Why would I need to replace my pinion gear? — Pinion gears are high-wear consumables on RC vehicles. After extended high-speed running, particularly on 8S brushless trucks, the teeth gradually wear, reducing efficiency and potentially causing slipping or noise. A new pinion gear restores smooth, quiet drivetrain operation. Additionally, if you've experienced a motor failure or collision, the pinion gear may have been damaged and requires replacement.
- What does the Safe-D5 design actually do? — The Safe-D socket has a D-shaped hole that matches your motor's D-profile shaft. Unlike traditional round-hole pinion gears that can slip if the set-screw comes loose, the Safe-D design locks mechanically to the motor shaft itself, preventing loss of drive even if the set-screw backs out. This is a game-changer for reliability on high-power brushless RC trucks.
- Is this suitable for beginners? — This is a replacement or upgrade part, not a complete drivetrain system, so it's most relevant to experienced RC enthusiasts who already own an ARRMA brushless truck. Beginners should purchase a complete Ready to Run (RTR) vehicle, but will find this useful later when they need replacement drivetrain components.
- What motor shaft size does this fit? — This pinion gear is designed for 5mm diameter motor shafts, which is standard on ARRMA brushless motors. Verify your motor shaft diameter before purchasing.
- Should I use the set-screw, E-clip, or both? — ARRMA supplies both the M4 x 4mm set-screw and the 3.2mm E-clip for redundancy and maximum security. Best practice is to use both — tighten the set-screw firmly and install the E-clip over the motor shaft end to prevent pinion gear rotation or axial movement.
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 Pinion Gear, 25T HD Mod1 Safe-D5 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.
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