Dongfeng FAST Gearbox Assy parts Reverse gear slide sleeve 12JSDX240T-1701108

As a critical component of the gearbox’s reverse gear system, this slide sleeve’s core function is to enable smooth and reliable engagement of the reverse gear by connecting the synchronizer hub to the reverse gear wheel. Its working mechanism is tightly linked to the gearbox’s shifting operation:

When the driver selects reverse gear, the shifting fork pushes the slide sleeve to slide axially along the synchronizer hub’s splines.

The slide sleeve’s internal dog teeth first engage with the reverse gear wheel’s external dog teeth (via a tapered synchronizing ring, which pre-synchronizes the rotational speeds of the hub and gear wheel to reduce engagement impact).

Once fully engaged, the slide sleeve transmits torque from the synchronizer hub to the reverse gear wheel, reversing the power flow and enabling the vehicle to move backward.

This mechanism not only ensures stable torque transmission (supporting the 12JSDX240T gearbox’s maximum reverse torque of 2400 N·m) but also reduces "gear grinding" noise during engagement

The slide sleeve features an optimized structural design to enhance engagement performance and durability:

Internal Spline & Dog Tooth Design: The internal splines (matching the synchronizer hub) are precision-machined with a tooth profile modification (tip chamfering: 0.5×45°) to reduce sliding resistance and prevent spline tooth damage during axial movement. The external dog teeth (engaging with the reverse gear wheel) have a hardened contact surface (HRC 58-62) and a tapered lead-in angle (15°) to facilitate smooth engagement.

Axial Guide Groove: The outer circumference of the slide sleeve is equipped with a U-shaped guide groove for the shifting fork. This groove has a polished surface (Ra ≤ 0.8 μm) to minimize friction between the fork and slide sleeve, ensuring precise and smooth axial sliding.

Lightweight Optimization: The slide sleeve’s sidewall features evenly distributed holes (3-4 holes, diameter 8 mm) to reduce weight (by ~15% compared to solid designs) without compromising structural strength—lowering the gearbox’s overall weight and improving vehicle fuel efficiency

To withstand high torque and frequent engagement impacts, the slide sleeve uses high-performance materials and specialized heat treatment:

Base Material: Made of 40CrNiMoA alloy steel—a material renowned for its high tensile strength (≥980 MPa), impact toughness (≥60 J/cm² at -40℃), and fatigue resistance. This material can endure the repeated torque loads and engagement impacts of reverse gear operation.

Heat Treatment: The entire slide sleeve undergoes carburizing and quenching treatment: the surface is carburized to a depth of 0.8-1.2 mm, then quenched and tempered to achieve a surface hardness of HRC 58-62 (for wear resistance) and a core hardness of HRC 30-35 (for toughness). This "hard surface, tough core" structure prevents surface wear and internal cracking under heavy loads.

Surface Finish: After heat treatment, the slide sleeve undergoes precision grinding and polishing to ensure dimensional accuracy (spline pitch diameter tolerance: ±0.02 mm) and smooth surface finish—reducing friction during sliding and extending the service life of mating components (e.g., synchronizer hub, shifting fork)

The reverse gear slide sleeve is primarily applied in Dongfeng FAST 12JSDX240T-equipped heavy-duty vehicles, including:

Dongfeng long-haul tractor-trailers (requiring reliable reverse gear operation for parking and loading/unloading in logistics hubs);

Mining dump trucks and construction vehicles (operating in rough terrain with frequent reverse maneuvers for positioning);

Heavy-duty cargo trucks (used for intercity bulk transport, where reverse gear engagement needs to be smooth to avoid component damage).

In terms of installation, it offers distinct advantages:

Direct OEM Replacement: Matches the original slide sleeve’s dimensions, spline specifications, and guide groove design—no modifications to the synchronizer hub or shifting fork are required. Installation only requires removing the gearbox upper cover and sliding the new sleeve onto the synchronizer hub, which can be completed with standard tools in 30-45 minutes.

Interchangeability: Fully interchangeable with the original FAST 12JSDX240T slide sleeve, ensuring consistent performance with other original gearbox components (e.g., synchronizing ring, reverse gear wheel).

Long Service Life: Under normal operating conditions (proper gearbox oil maintenance), the slide sleeve has a service life of over 120,000 km, reducing the frequency of gearbox overhauls and lowering maintenance costs for fleet operators