FAW Rear Suspension: A Critical Focus on the 35 Components of a 6×4 Drivetrain

Welcome to this critical technical guide on the FAW Rear Suspension assembly (Assembly 509). This is the complete, heavy-duty “tandem-axle” suspension system for the FAW Jiefang CA4251P66K24T1A3E5 6×4 diesel semi-trailer tractor. This is the assembly that handles the entire payload and provides traction.

The FAW Rear Suspension is a “logic” system known as a “balance beam” or “trunnion” suspension. Its design is critical for a 6×4 tractor, as it is engineered to articulate and “walk” over uneven terrain, ensuring all eight rear wheels remain in contact with the ground for maximum traction and load distribution.

This in-depth guide is an essential resource for professional chassis technicians, fleet managers, and parts specialists. We will deconstruct the entire FAW Rear Suspension into its 35 serviceable component types, including the ‘Rear leaf spring assembly’, the ‘Balance suspension bracket’, the ‘Thrust rods’, and the vast array of high-tensile fasteners that hold this high-stress system together.

Core Component: The ‘Rear Leaf Spring Assembly’ (2912010-2000)

The heart of the FAW Rear Suspension is the ‘Rear leaf spring assembly’ (2912010-2000). The list calls for two of these—one for each side of the truck. Unlike a front suspension, this is an “inverted” leaf pack. The “pack” consists of multiple leaves of high-carbon spring steel, such as ‘Rear leaf spring-first leaf’ (2912011-2000) through ‘Rear leaf spring-fourth leaf’ (2912014-2000).

The “logic” of this FAW Rear Suspension is completely different from the front. The center of this spring pack (held by ‘Center bolt-rear leaf spring’ 2912161-70A) rests on the ‘Balance suspension bracket’ (trunnion), which is the central pivot point on the chassis. The *ends* of the spring pack rest on the two rear drive axles.

This creates a “walking beam” effect. When the front-most drive axle hits a bump, it pushes *up* on the front of the spring pack; this, in turn, forces the *back* of the spring pack *down*, pushing the rear-most drive axle onto the ground. This “walking” articulation is the core logic of the FAW Rear Suspension, ensuring constant, maximum traction for both axles.

The “Logic”: ‘Balance Suspension Bracket’ (Trunnion)

The central pivot for this “walking” FAW Rear Suspension is the ‘Balance suspension bracket’ assembly (see Assembly 499). This is the heavy-duty bracket that mounts to the truck’s frame rail. The parts in this list are what attach the leaf spring *to* that trunnion.

The ‘Balance suspension bracket pin upper/lower cover’ (2918041-1057, 2918046-1057) and ‘Bushing-balance suspension bracket pin’ (2918042-242) form the “bearing” that the leaf spring pack pivots on.

The ‘Cover-balance suspension bracket spring’ (2918072-1050) is the “cap” that holds the spring pack down onto this trunnion. This entire “logic” assembly is what allows the inverted ‘Rear leaf spring assembly’ to pivot in the center, creating the “walking beam.” This is the most critical pivot point in the entire FAW Rear Suspension.

Axle Connection: U-Bolts and Thrust Rods

The FAW Rear Suspension must not only support weight, but it must also hold the two drive axles in perfect alignment. This is done by two systems.

**1. U-Bolts:** The ‘U-bolt-fasten rear leaf spring’ (2912411-70A) units (4 total) are what “clamp” the axles *to* the ends of the leaf spring packs. They pass through the ‘Cover-rear leaf spring’ (2912406-1057) and are secured by the eight ‘Nut-fasten U-bolt’ (2912413-5H). This is the primary vertical connection.

**2. Thrust Rods:** Leaf springs are not strong enough to handle the immense acceleration and braking torque (which tries to “twist” the axle). This is the job of the “thrust rod” (or “torque rod”) system. This FAW Rear Suspension parts list includes the ‘Upper front/rear connecting rod with rubber bushing’ (2919005-242, 2919015-242) and the ‘Lower front/rear connecting rod with rubber bushing’ (2919010-242, 2919020-242).

This “logic” creates a “four-link” system for each axle. These four rods (two upper, two lower) form a rigid “box” that connects the axle directly to the frame, forcing it to stay perfectly aligned. The ‘Support-upper reaction rod and vehicle frame connecting’ (2919111-2000) is the chassis-side bracket for these rods. This thrust rod system is the “logic” that handles all the acceleration and braking forces, leaving the FAW Rear Suspension leaf springs to simply handle the vertical load.

Critical Fasteners: The 100+ Piece Hardware Set

The FAW Rear Suspension is a high-stress, high-vibration assembly held together by over 100 specialized fasteners. A single failed bolt here could be catastrophic.

**SPL Self-Locking Nuts (T327-series):** The parts list calls for a total of **52** ‘SPL hex small flange lock nuts’ (T32718TF2, T32720TF2, T32724TF2). This is the “logic” of a modern, high-safety FAW Rear Suspension. These are “Stover” or “prevailing-torque” lock nuts. The top of the nut is intentionally crimped or deformed, creating an “elastic” lock that grips the bolt threads. This makes them *immune* to vibration and *must* be used for all critical connections, especially on the thrust rods.

**Flange Bolts (Q185-series):** The list calls for over 40 ‘Hex flange bolts’ (Q1851875T, Q1851850T, Q1852060T, Q1852090T, Q1851860T). The “flange” head acts as an integrated washer to spread the clamping load. The “T” suffix denotes a high-tensile (e.g., 10.9) strength, essential for handling the shear forces of the FAW Rear Suspension.

**Flange Nuts (C039714):** The 12 ‘Hex flange nuts’ provide a wide, secure clamping base for other non-locking-nut applications. This comprehensive, over-engineered fastener set is the “logic” that ensures the FAW Rear Suspension stays intact under the most extreme conditions.

FAW Rear Suspension Parts List (1/2)

The following table provides the first part of the detailed breakdown for the FAW Rear Suspension (509) diagram for the FAW CA4251P66K24T1A3E5 tractor.

FAW Rear Suspension Parts List (2/2)

This table details the remaining components for the FAW Rear Suspension, focusing on the thrust rod system and fasteners.

Technical Specifications and Assembly Context

The specifications for the FAW Rear Suspension are defined by its function as a heavy-duty, tandem-axle “walking beam” suspension. The FAW Rear Suspension is a comprehensive system for load-bearing and traction.