GPM Racing 20CRMNTI Steel M1.5 Spur Gear 35T+ Transmission Input Gear 20T (1.0 Mod) for Traxxas 1/6 4WD XRT 8S-78086-4 (XRT3520S)

Aftermarket steel spur and input gear for TRAXXAS XRT 8S

This aftermarket gear set is an RC-scale replacement designed for select TRAXXAS XRT and X-Maxx 8S platforms. The kit uses 20CrMnTi steel for the major gears and adds a 7075 aluminium fixed mount plus bearings to form a three-point support, which improves load distribution and transmission stability compared with the original two-point support design.

The set combines a 35T spur gear with M1.5 module and a 20T transmission input (motor) gear with M1.0 module in an integrated motor-gear and input-shaft arrangement that removes the older 2.5mm locating pin. Key measured values supplied by the manufacturer include a 35T spur with a 6mm diameter D-shaped motor hub opening, 14mm tooth width and approximately 55.4mm outer diameter, and a 20T motor gear with 1.0 module.

Use this kit where the goal is to reduce wear and improve gear mesh consistency under high torque from 8S-power setups. Note the part is specifically not suitable for TRAXXAS 1/5 X-Maxx 8S Monster Truck-77096-4 as stated by the manufacturer.

Packing includes

• Spur Gear 35T M1.5 – 1pcs
• Transmission Input Gear 20T (1.0 Mod) – 1pcs
• Aluminium 7075 Mount – 1pcs
• Bearing 6x13x5 – 1pcs
• Shim 6x8x3.5 – 1pcs
• Shim 6x8x7.5 – 1pcs
• Set Screws 5×5 – 1pcs

Original Name / Part No:

7785X+7786X

Compatible Models

• TRAXXAS 1/6 4WD XRT 8S-78086-4
• TRAXXAS 1/5 X-Maxx 8S Monster Truck-77086-4
• TRAXXAS 1/6 XRT Ultimate 8S-78097-4
• TRAXXAS 1/5 X-Maxx 8S Ultimate-77097-4

For builders and repairers of 8S TRAXXAS XRT and X-Maxx models, this GPM kit upgrades the OEM spur and input gears to hardened 20CrMnTi steel and includes a 7075 mount to enhance wear resistance and transmission steadiness under high load.

How do I verify chassis compatibility?

Confirm your vehicle matches the compatible models listed above and cross-check original part numbers where possible to ensure correct fitment before installation.

What are the key materials and benefits?

The main gears are 20CrMnTi steel and the mount is 7075 aluminium; this combination increases durability and improves load distribution compared with the stock parts.

Is the motor locating pin needed?

No. The integrated motor-gear and input-shaft design provided removes the need for the 2.5mm locating pin previously used.

Does this replace specific OEM part numbers?

The kit is intended as a replacement for the original spur and input gears referenced by part numbers 7785X+7786X, but confirm fitment against your chassis prior to fitting. Write Product Review Please sign in your account before you can write any review. Sign In Close

Made to order: GPM Racing parts are shipped to us from GPM’s factory, so please allow around 14 days for dispatch.