Traxxas Slash 2WD Short Course Truck Gearing Guide

Traxxas Slash RC Gearing & Optimization Guide

Optimizing your gear ratio is one of the most effective ways to balance speed, torque, and electronics longevity in your Traxxas Slash 2WD Short Course Truck. The relationship between your pinion gear (attached to the motor) and your spur gear (attached to the transmission) dictates how hard your motor has to work — and on a 1/10 short course truck platform with a 2.72 internal transmission ratio, even a single-tooth pinion change shifts your final drive ratio by 3-5%.

The Traxxas Slash 2WD is one of the most popular bashing and entry-level racing platforms in the 1/10 short course class. Because the Slash uses a relatively tall internal transmission ratio and rides on large 2.2/3.0 truck tires, gearing decisions have an outsized effect on motor temperature, runtime, and acceleration off the line. Most stock Slash setups ship with an 86T spur and a 23T or 28T pinion paired with the Titan 12T brushed motor, but brushless conversions and racing setups frequently move to higher tooth-count pinions to take advantage of the wider RPM band.

🛠️ Essential Tools Required for Gearing Changes

• Hex drivers (1.5mm, 2.0mm, or 2.5mm depending on the Traxxas Slash variant)
• Paper strip (for setting precise gear mesh)
• Infrared temperature gun (crucial for monitoring motor heat after each run)
• Threadlock (for the pinion gear grub screw)
• Pinion gear puller (recommended when swapping gears on a hot motor shaft)

📋 Comprehensive Gearing & Temperature Guide

1. Understanding Pinion vs. Spur Gear Adjustment

Changing your gears alters your final drive ratio. Installing a larger pinion gear or a smaller spur gear increases top-end speed but increases the load on the motor, causing it to run hotter. Conversely, a smaller pinion or larger spur increases torque and acceleration while lowering top speeds and keeping your motor cool. On the Traxxas Slash, this trade-off is amplified by the fixed 2.72 internal ratio — small external changes have a direct thermal consequence.

2. How to Set a Perfect Gear Mesh

Improper gear mesh will quickly strip your spur gear or bind your drivetrain.

1. Loosen the motor mount screws slightly.
2. Place a small strip of standard notebook paper between the pinion and spur gear teeth.
3. Press the gears tightly together and tighten the motor mount screws.
4. Roll the paper out. The paper should have clean, crisp crinkles without ripping.

Recommended Pinion & Spur Chart

All combinations use a 86T 48-pitch spur. FDR is calculated as (spur ÷ pinion) × 2.72 internal ratio.

Understanding Pinion & Spur Gears

Stepping up one pinion tooth on a Slash drops your FDR by roughly 4-5%, which translates to a measurable top-speed increase but also raises motor and ESC temperatures. Stepping down by one tooth gives you noticeably punchier corner exits and lower temps, at the cost of top speed on the straights. The 86T 48-pitch spur is the de facto standard; swapping to a lighter aluminum spur hub will shed rotational mass and improve throttle response without changing the ratio itself.

Rollout Targets

Rollout on a Slash is calculated using the outer diameter of the rear tire (typically 4.3 inches on SCT BFGoodrich tires) and the final drive ratio. Because short course tires are tall and heavy, a lower rollout (around 1.85 to 2.05 inches per motor revolution) is preferred for technical tracks, while open parking lot bashing tolerates a taller rollout of 2.3 inches or more.

Motor Temperature Management

Slash motors should be pulled off the track and checked with an infrared thermometer the moment runtime ends. A brushless 17.5T should stay under 160F (71C); a brushed Titan 12T should stay under 180F (82C). If you see numbers above those thresholds, drop one or two pinion teeth before the next run. ESCs typically run 10-20F cooler than the motor; if the ESC is hotter than the motor you likely have a binding driveline or a slipping slipper clutch wasting energy as heat.

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