ARRMA ARA311125 37T Mod1 Safe-D8 Pinion Gear 8mm Shaft

The ARRMA ARA311125 37T Mod1 Safe-D8 pinion gear is a tough steel motor pinion for RC vehicles using Mod1 gearing and an 8mm D-shaped motor shaft, providing reliable power transfer for high-load ARRMA drivetrain setups.

This genuine ARRMA pinion is precision manufactured with a wide tooth profile for smooth gear mesh and consistent drivetrain operation. The Safe-D8 design uses a D-shaped bore to match the motor shaft profile, helping maintain drive and braking control if the set screw loosens during use.

Features

• Genuine ARRMA Part: Factory replacement or tuning pinion gear for compatible ARRMA vehicles
• 37T Gear Count: Provides a 37 tooth gearing option for Mod1 drivetrain setups
• Mod1 Tooth Profile: Designed for vehicles using Mod1 pitch spur gears
• Safe-D8 Bore Design: D-shaped 8mm bore matches compatible motor shafts to help retain drive if the set screw backs out
• Steel Construction: Strong and durable material suited to demanding RC use
• Wide Tooth Profile: Precision manufactured for smooth operation when correctly meshed with a compatible spur gear
• Threaded Set Screw Hole: Accepts the included M4 x 4mm set screw for secure motor shaft mounting
• E-Clip Retention: Includes a 6mm E-clip for additional motor shaft pinion retention

Specifications

• Brand: ARRMA
• Part Number: ARA311125
• Barcode: 5052127043458
• Product Type: Motor pinion gear
• Tooth Count: 37T
• Gear Pitch: Mod1
• Pinion Type: Safe-D8
• Motor Shaft Size: 8mm D-shaped shaft
• Material: Steel
• Set Screw Size: M4 x 4mm
• E-Clip Size: 6mm
• Intended Use: Replacement or gearing adjustment part for compatible ARRMA RC vehicles using Mod1 gears and an 8mm D-shaped motor shaft

Includes

• 1 x ARRMA 37T Mod1 Safe-D8 pinion gear
• 1 x M4 x 4mm set screw
• 1 x 6mm E-clip

FAQ

What motor shaft size does this pinion fit? The ARRMA ARA311125 pinion gear is designed for compatible 8mm D-shaped motor shafts.

What does Safe-D8 mean? Safe-D8 refers to the D-shaped 8mm bore design, which matches the motor shaft profile so drive and braking are less likely to be lost if the set screw loosens.

Does this pinion include a set screw? Yes. This pack includes one M4 x 4mm set screw and one 6mm E-clip.

Will this fit any RC car with Mod1 gearing? No. OZRC recommends checking your vehicle manual, motor shaft diameter, spur gear pitch and required tooth count before fitting this pinion.

Important Notes

• Check your ARRMA vehicle manual to confirm ARA311125 is the correct pinion gear before ordering.
• This pinion suits 8mm D-shaped motor shafts only.
• Use only with compatible Mod1 spur gears.
• Apply suitable thread lock to the set screw when installing onto a metal motor shaft.
• Set gear mesh correctly after installation to reduce noise, heat and premature gear wear.
• Changing pinion size can affect motor temperature, speed, acceleration and runtime.