INJORA 24T/10T Underdrive Helical Gear Set for TRX4M RC Crawler (1 Set)
INJORA 24T/10T Underdrive Helical Gear Set for TRX4M RC Crawler (1 Set)
This 24-tooth ring and 10-tooth pinion helical gear set from INJORA is a steel underdrive upgrade for 1/18 TRX4M RC crawler axles. CNC machined from 20CrMo alloy steel, it replaces stock plastic gears to provide a 16.7% underdrive ratio, which can improve climbing performance when installed on the front or rear axle.
What This Gear Set Brings to Your TRX4M
Helical gears offer greater strength and smoother operation than factory spur gears because their angled teeth engage gradually. With CNC-machined 20CrMo alloy steel construction, this set delivers less vibration, less noise, and less wear compared to stock plastic gears. By installing this gear set, you introduce a 16.7% underdrive to the chosen axle, which reduces wheel speed there relative to the other end. Typically, underdriving the rear (or overdriving the front) helps the front wheels pull faster, allowing the rig to climb better and reduce the tendency to roll over on steep inclines.
Technical Details
| Gear Type | Helical ring and pinion |
| Tooth Count | 24T ring / 10T pinion |
| Material | 20CrMo Alloy Steel |
| Machining | CNC |
| Underdrive | 16.7% |
| Compatibility | INJORA TRX4M front or rear axle |
| Quantity per Axle | 1 set (ring + pinion) |
Installation Tips to Get It Right
Each axle requires one set of gears (one ring and one pinion). Important: do not mix gears from this set with gears from any other set, even if the tooth counts appear the same — tooth profiles may differ. After installation, if you notice free play between the pinion and ring gear, add one or two shims between the pinion gear and the bearing to push the pinion teeth deeper into the ring gear teeth.
How does underdrive affect climbing?
Installing this gear set on the rear axle underdrives the rear, effectively overdriving the front. This causes the front wheels to rotate faster than the rear, pulling the vehicle forward over obstacles and reducing the chance of flipping backward on steep climbs. Alternatively, installing it on the front axle underdrives the front, which can be used to balance handling in technical sections.
Answers to Common Questions
Does this gear set fit my TRX4M?
Yes, it is designed specifically for the 1/18 TRX4M RC crawler, front or rear axle.
What material are these gears made of?
They are CNC machined from 20CrMo alloy steel, known for strength and durability.
Can I mix this set with other gears?
No, INJORA advises not to swap gears from different sets, even if they have the same tooth count, as tooth profiles may differ.
What if the gears feel loose after installation?
You can add one or two shims between the pinion gear and the bearing to reduce free play.