Sinotruk Transmission Double H Valve

1. Basic Part Information

• Part Name: Double H Valve Assembly (also known in the repair industry as a pneumatic control valve or high/low range shift valve)

• Part Number: WG2203250003 (or the earlier AZ2203250003 — both typically refer to the same or a highly interchangeable component)

• Appearance Features:

  • Body Material: Die-cast aluminum, dark gray — lightweight, good heat dissipation, corrosion resistant.

  • Air Ports: Multiple quick-connect pneumatic ports (indicated by blue pull-rings) for connecting/disconnecting different air circuits.

  • Adjustment/Mounting Holes: Threaded holes (marked as M14 × 1.5) for mounting bolts or adjustment rods.

  • Exhaust Port: A metal mesh screen (multiple holes) for venting/exhausting internal air circuits.

  • Batch Info: Cast batch number on the valve body (e.g., JT2203250003, batch 2024B05-28) indicating a qualified part from a specific production run.

2. Function & Role

• High/Low Range Shifting: The double H valve controls the transmission shift cylinder. When the driver operates the range selector (high/low switch) on the shift lever in the cab, the internal shift fork shaft moves and sends a pneumatic signal to the double H valve. The valve then switches internal air passages, redirecting compressed air flow — which moves the piston inside the transmission shift cylinder — completing the shift between high range and low range.

• Pneumatic Control: It acts as the "bridge" between the driver's control signal (from the cab) and the mechanical action inside the transmission, using compressed air from the vehicle's air reservoir as its power source.

• Pressure Holding & Positioning: After a shift is completed, the double H valve maintains the closed air circuit, ensuring the shift cylinder piston stays in the correct position — preventing unintended gear disengagement (jumping out of gear).

3. Applicable Vehicles & Transmissions

This double H valve is highly versatile and widely used across Sinotruk's heavy-duty truck lineup and their matching transmissions:

• Applicable Vehicles: HOWO, Steyr, SITRAK, Hohan, and other Sinotruk series heavy-duty trucks.

• Compatible Transmissions:

  • Sinotruk HW series transmissions (e.g., HW19710L, HW19712L, HW15710, etc.)

  • Suitable for 10-speed and 12-speed transmissions that use a high/low (double H) shift configuration.