FAW Hydraulic Support Device For The Cab: 5 Critical Pivot Components for Tilt Safety

Welcome to this critical technical deep dive into the FAW Hydraulic Support Device For The Cab (Lower Mount Assembly). This component group is the structural pivot and anchor point for the hydraulic cab tilt cylinder on the FAW Jiefang CA4251P66K24T1A3E5 6×4 diesel semi-trailer tractor. Its “logic” is to create a secure, high-strength pivot, allowing the hydraulic cylinder to articulate safely as it lifts the entire weight of the cab.

The FAW Hydraulic Support Device For The Cab is not the cylinder itself, but the assembly of hardware that connects the “eye” (lower loop) of the cylinder to the main chassis frame. This “pivot logic” is a high-stress, high-shear application. It must be strong enough to withstand the immense forces of lifting the cab, and durable enough to resist the constant, high-frequency vibrations from the engine and road.

This in-depth guide is an essential resource for chassis technicians and service managers. We will deconstruct the entire FAW Hydraulic Support Device For The Cab into its 5 primary component types. We will analyze the main ‘Pivot Pin’ (the core MSU), the vibration-damping ‘Soft Pads’, and the critical, multi-stage “anti-vibration” fastener system that holds it all together.

MSU 1: The “Kingpin” – The Logic of the Lower Pivot Pin (5002023AB85)

This component, the ‘Pin-hydraulic cylinder lower fixed point’ (5002023AB85), is the “longer” and most critical MSU in the entire FAW Hydraulic Support Device For The Cab. This single pin is the “axle” on which the entire hydraulic cylinder pivots.

Shear-Load Logic: The “logic” of this pin is to handle extreme shear force. When the hydraulic cylinder is actuated to lift the multi-ton cab, the entire weight and force is concentrated on this one pin. It is designed to resist being “sliced” in half. To achieve this, this MSU is not a simple bolt; it is a precision-ground, high-tensile, hardened steel dowel.

Construction: This pin is likely made from a high-carbon alloy steel (like 4140) that has been case-hardened. This process creates an ultra-hard, wear-resistant outer “skin” while maintaining a slightly softer, more ductile core. The “logic” of this metallurgy is to provide a surface that resists wear from the pivoting bushings, while the core remains tough and resistant to the shock loads that could snap a brittle, fully-hardened pin. The surface is also polished to a low-friction finish to allow for smooth rotation.

Serviceability (MSU): This pin is a primary MSU and a key wear item. Over tens of thousands of tilt cycles, or from high vibration, the pin can begin to wear, creating a “clunking” or “slop” in the lower cab mount. During service of the Entry_ID_475 (Cab Tilting Cylinder), this pin must be inspected. If any scoring, pitting, or “ovaling” (uneven wear) is present, the pin must be replaced. Failure to replace a worn pin will lead to the rapid destruction of the ‘Soft Pads’ (MSU 3) and eventual failure of the entire FAW Hydraulic Support Device For The Cab.

MSU 3 & 4: The Vibration Damping “Logic” (Pads & Washer)

This group of components provides the “cushioning” and spacing logic for the FAW Hydraulic Support Device For The Cab.

1. ‘Soft pad-hydraulic cylinder lower fixed point’ (5002027-A01): The parts list calls for two (2) of these critical MSUs. These are the bushings for the pivot. Their “logic” is to prevent metal-on-metal contact.

These pads are placed on either side of the cylinder’s “eye,” sandwiched between the cylinder and the chassis-mounted bracket. They are made from a high-durometer polymer or nylon. This design provides three functions:

• Vibration Damping: They absorb high-frequency vibrations from the engine/chassis, protecting the hydraulic cylinder’s seals from damage.
• Noise Prevention: They prevent the “squeaking” and “groaning” that would come from a steel-on-steel pivot.
• Sacrificial Wear: They are designed to be the “sacrificial” component. They are much cheaper to replace than the pin or the cylinder.

2. ‘Large washer’ (Q40218): This single MSU works with the fastener system. Its “logic” is load distribution. It is placed on the outside of the chassis bracket, providing a large, flat surface for the nut to tighten against. This prevents the nut from “digging into” or “ovaling” the hole in the bracket, ensuring the FAW Hydraulic Support Device For The Cab remains securely clamped.

MSU 2 & 5: The “Anti-Vibration” Fastener Logic

This final group of MSUs is the hardware that secures the main ‘Pivot Pin’. The “logic” here is all about anti-vibration, a critical safety feature for the FAW Hydraulic Support Device For The Cab. The system uses two different nuts.

1. ‘Hexagon flange nut’ (Q039620): This is likely the “primary” nut. The pin (MSU 1) is threaded on its end, passes through the bracket, the bushings, and the cylinder eye, and exits the other side. This nut, along with the ‘Large washer’ (MSU 4), is tightened to set the correct “preload” on the soft pads. The “flange” logic means it has an integrated washer, providing a wide, secure clamping face.

2. ‘Type 1 non-metallic insert hexagon lock nut’ (Q32918T): This is the most critical safety component in the FAW Hydraulic Support Device For The Cab. This is a “Nyloc” nut. Its “logic” is to be a *jam nut* or *locking nut*.

It is threaded onto the pin *after* the primary nut (Q039620). The internal nylon ring binds tightly to the threads, creating a powerful “prevailing torque” that *prevents* the primary nut from backing off due to vibration. A standard nut *will* vibrate loose. This dual-nut, self-locking system is what guarantees the pivot pin cannot fall out, which would cause the cab to become detached from the tilt cylinder.

Serviceability (MSU): Both nuts are MSUs. The ‘Lock nut’ (Q32918T) is **strictly a single-use part**. Once it is removed, the nylon insert is permanently deformed and loses its locking ability. It *must* be replaced with a new nut every single time the FAW Hydraulic Support Device For The Cab is serviced.

FAW Hydraulic Support Device For The Cab Parts List

The following table provides the complete, detailed breakdown of all 5 component types identified in the FAW Hydraulic Support Device For The Cab (Lower Mount) diagram for the FAW CA4251P66K24T1A3E5 tractor.

Technical Specifications and Assembly Context

The specifications for the FAW Hydraulic Support Device For The Cab are defined by its function as a high-shear, anti-vibration pivot point. All components are critical safety MSUs.