Dongfeng FAST Gearbox Assy part Pull fork RTD1707067010018

As a critical link between the gearbox’s shifting control and sliding sleeve, this pull fork’s core function is to convert the rotational motion of the shifting shaft into linear motion of the sliding sleeve, enabling smooth engagement or disengagement of gears. Its working mechanism is tightly linked to the gearbox’s shifting process:

When the driver operates the gear lever, the shifting linkage drives the shifting shaft to rotate.

The pull fork, fixed to the shifting shaft via a spline connection, rotates with the shaft and uses its fork-shaped end to push or pull the sliding sleeve along the synchronizer hub.

This linear movement of the sliding sleeve brings its internal dog teeth into engagement with the target gear’s external teeth (after synchronization), completing the gear shift.

The pull fork’s precision directly determines shifting smoothness—any deviation can cause "gear grinding," shifting delay, or even gear disengagement during driving

The pull fork features an optimized structural design to enhance shifting accuracy and reduce wear:

Fork Body & Fork Foot Design: The fork body adopts a curved, lightweight structure (thickness: 8-10mm) that balances rigidity and weight, reducing the load on the shifting shaft. The fork foot (the part in contact with the sliding sleeve) has a U-shaped groove with a polished inner surface (Ra ≤ 0.8μm) and a slight taper (5°) at the edges—this design minimizes friction between the fork and sliding sleeve, preventing premature wear and ensuring smooth sliding.

Mounting Interface: The spline hole at the fork’s base (for connecting to the shifting shaft) is precision-machined with a tolerance of H7, ensuring a tight fit with the shifting shaft’s splines (fit clearance: 0.02-0.05mm). This eliminates backlash between the fork and shaft, ensuring precise transmission of shifting force.

Reinforcement Features: Key stress points (e.g., the junction between the fork body and fork foot) are reinforced with fillets (radius: 3-5mm) to distribute stress and prevent cracking under repeated shifting loads

To withstand frequent shifting impacts and friction, the pull fork uses high-performance materials and specialized surface treatment:

Base Material: Made of 45# carbon steel—a material chosen for its high tensile strength (≥600 MPa), good ductility, and cost-effectiveness. It is suitable for the moderate load and impact conditions of heavy-duty gearbox shifting. For higher-load applications, some variants may use 40Cr alloy steel (tensile strength: ≥980 MPa) for enhanced durability.

Heat Treatment: The entire pull fork undergoes normalizing and quenching-tempering treatment: normalizing (at 850-900℃) refines the grain structure to improve uniformity, while quenching-tempering (quenching at 840℃, tempering at 550℃) achieves a core hardness of HRC 28-32—balancing toughness and strength to resist bending or breaking.

Surface Treatment: The fork foot’s contact surface (in contact with the sliding sleeve) is treated with nitriding (surface hardness: HV 500-600, nitriding layer depth: 0.3-0.5mm). This treatment significantly improves wear resistance, reducing the rate of fork foot wear by 40-50% compared to untreated surfaces

The pull fork is primarily applied in Dongfeng FAST RTD-series gearboxes for heavy-duty vehicles, including:

Dongfeng mining dump trucks (operating in harsh off-road conditions with frequent low-speed, high-torque shifting);

Heavy-duty cargo trucks for long-distance bulk transport (requiring smooth high-speed range shifting to optimize fuel efficiency);

Engineering vehicles like large loaders and road rollers (exposed to high vibration and repeated shifting during operation).

In terms of installation, it offers distinct advantages:

Direct OEM Replacement: Matches the original pull fork’s dimensions, spline specifications, and fork foot shape—no modifications to the shifting shaft or sliding sleeve are needed. Installation only requires removing the gearbox upper cover, disconnecting the old fork from the shifting shaft, and sliding the new fork into place, which can be completed with standard tools in 20-30 minutes.

Interchangeability: Fully interchangeable with the original FAST RTD pull fork, ensuring consistent shifting performance when used with other original components (e.g., shifting shaft, sliding sleeve).

Long Service Life: Under normal operating conditions (with proper gearbox oil maintenance), the pull fork has a service life of over 150,000 km, reducing the frequency of gearbox overhauls and lowering maintenance costs for fleet operators