4WD Car Kit with Differential Control, Gearbox Crawler Chassis Frame – with Differential Portal Axle, High/Low Speed for TRX-4

Specifications

• Wheelbase: 313mm (Standard 1/10 Scale)
• Chassis Type: Metal Frame Rails with Nylon Axle Housings
• Drive System: 4WD Shaft Drive with Steel Universal Joints
• Axle Type: Portal Axles (Increased Ground Clearance)
• Transmission: 2-Speed Gearbox (Switchable High/Low Range)
• Differentials: Remotely Lockable Front & Rear (Cable driven)
• Motor: 550 Brushed Motor (35T High Torque) - Pre-installed

      Servos Included:

• 1x Shift Servo (for 2-speed transmission)
• 1x Diff Lock Servo (for locking differentials)
• Suspension: Oil-Filled Metal Shock Absorbers
• Weight: ~2.8 kg (Heavyweight for traction)

Applications

• Scale Rock Crawling: The portal axles and heavy weight provide a low center of gravity (CG) and exceptional clearance for technical crawling.
• Custom Truck Builds: The 313mm wheelbase fits a wide variety of hard bodies (e.g., Defender D110, Cherokee, Bronco styles).
• FPV Rover Platform: Due to its stability and suspension, this chassis makes an excellent base for mounting FPV cameras for long-range ground exploration.

Project Evolution

• Prerequisites: Familiarity with basic RC electronics (binding receivers, calibrating ESCs).
• Feature Upgrade: If you are upgrading from a standard SCX10-style rig, this chassis unlocks Selectable Locking Differentials. You can run open diffs for a tighter turning radius on trails, then lock them instantly from your transmitter for 100% traction on loose climbs.
• Effort Level: Intermediate to Advanced. Requires installing your own Radio System, ESC, and Battery.
• Probots Tech-Bridge: We back this hardware with local engineering support. If you're unsure about the servo linkages or gear ratios, our team in Bangalore understands these mechanical systems and can guide your setup.

Virtual Technician & Wiring Guide

• ⚠️ ESC Requirement: The included 550 motor requires a Brushed ESC capable of at least 60A (e.g., Hobbywing 1060 or 1080).
• Servo Voltage: Ensure your BEC can handle the load of the steering servo plus the shift/diff servos. A 5A external BEC is recommended for peak performance.
• Receiver Channels: To fully utilize this chassis, you need a transmitter/receiver with at least 4 Channels:
• CH1: Steering
• CH2: Throttle (ESC)
• CH3: 2-Speed Shifting
• CH4: Diff Lock Control

Package Includes:

• 1x Assembled AX-8508 Chassis Frame
• 4x Crawler Wheels & Tires (Pre-mounted)
• 1x 550 Brushed Motor (Pre-mounted
• 3x Micro Servos (Shift/Diff)

Frequently Asked Questions (FAQ)

• Does this chassis come fully assembled?
  Yes, the AX-8508 comes pre-assembled with the motor, gearbox, axles, and servos installed. You only need to add your electronics (ESC, Rx, Battery).
• Is the wheelbase adjustable?
  The standard wheelbase is 313mm. While the links are fixed length, you can customize the wheelbase by purchasing different length links separately.
• Are the gears metal or plastic?
  The internal transmission gears and axle gears are metal for durability. The spur gear is typically nylon to reduce noise and act as a mechanical fuse.
• Can I use a brushless motor with this?
  Yes, the motor mount accepts standard 540/550 size motors. You can swap the included brushed motor for a brushless system if you have a compatible ESC.
• What body shells fit this chassis?
  Any standard 1/10 scale crawler body with a 313mm wheelbase (like the TRX-4 Defender or Bronco bodies) will fit, though body mounts may need adjustment.
• Do the portal axles actually help?
  Yes, portal axles increase the ground clearance at the differential by approximately 10-15mm, allowing you to drive over obstacles that would snag straight axles.
• How do I control the 2-speed transmission?
  The transmission has a shifting servo pre-installed. You connect this to an auxiliary channel (e.g., CH3) on your receiver to toggle between High and Low gears.
• How do the locking differentials work?
  Bowden cables connect the diff lock mechanisms to a servo. Actuating the servo engages a locking dog in the axle, forcing both wheels to turn at the same speed.
• What is the gear ratio?
  The exact ratio depends on the gear selection, but the Low gear is optimized for high-torque crawling, while High gear provides trailing speed.
• Does it include wheels and tires?
  Yes, this kit includes 4 high-grip crawler tires mounted on wheels. It is a complete rolling chassis ready for your body shell.
• What battery voltage is supported?
  The chassis mechanics handle 2S or 3S LiPo power easily. The actual voltage limit depends on the ESC you choose to install.
• Is the frame rail carbon fiber or metal?
  The main chassis rails are made of metal (steel/aluminum alloy) for maximum rigidity and realistic weight.
• Will a standard 2-channel radio work?
  You can drive it with 2 channels (Steering + Throttle), but you will lose the ability to shift gears or lock diffs remotely.
• Are spare parts available?
  Common wear items like drive shafts and gears are compatible with many standard aftermarket crawler parts (often cross-compatible with TRX-4 or SCX10 II standards).
• Does it have a slipper clutch?
  Yes, the transmission input shaft features a slipper clutch to protect the drivetrain from shock loads during hard binding.
• What is the servo connector type?
  All pre-installed servos use standard 3-pin JR/Futaba style connectors compatible with all hobby-grade receivers.
• Can I remove the portal axles?
  Technically yes, but the chassis is designed for them. Converting to straight axles would require changing the suspension geometry and links.
• Is the motor waterproof?
  Brushed motors are generally water-resistant, but they are not rated IP67. Mud and water will shorten the brush life if not cleaned.
• How heavy is the shipping package?
  The shipping weight is approximately 3.2 kg including packaging materials.