- ChangChun City, Jilin Province, China
by 
Welcome to this critical technical guide on the FAW Main Box Left-Lower Centre Shaft Assembly (Part No. 1701271-A2V). This is a complete, load-bearing gear and shaft set for the main gearbox of the FAW Jiefang CA4251P66K24T1A3E5 6×4 diesel semi-trailer tractor.
The FAW Main Box Left-Lower Centre Shaft Assembly, also known as a “counter-shaft,” is the literal workhorse of the transmission. This gearbox uses a “twin-countershaft” design, meaning it splits the engine’s torque between this shaft and an “Upper Right” shaft. This design is the key to its heavy-duty torque capacity.
This in-depth guide is an essential resource for professional transmission technicians and parts specialists. We will deconstruct the entire FAW Main Box Left-Lower Centre Shaft Assembly into its 14 serviceable components, including the main shaft, all of its drive gears, the critical bearings, and all associated locking hardware.
The main gearbox of this FAW tractor uses a **twin-countershaft** (or “twin-shaft”) design. This is the gold standard for heavy-duty applications. Instead of one large countershaft handling 100% of the engine’s torque, the load is “split” 50/50 between two smaller, identical countershafts.
This assembly, the FAW Main Box Left-Lower Centre Shaft Assembly, is one of those two critical shafts. By splitting the torque, the “separating forces” (the forces of the gear teeth trying to push each other apart) are balanced. This dramatically reduces the stress on the transmission housing and the bearings, allowing the gearbox to be lighter, more compact, and significantly more durable.
The “logic” of this system requires that both the FAW Main Box Left-Lower Centre Shaft Assembly and its “Upper Right” twin are perfectly “timed” so that their helical gear teeth engage the main shaft at the exact same instant. If the timing is off by a single tooth, one shaft will take the entire load, leading to its rapid and catastrophic failure.
The backbone of the FAW Main Box Left-Lower Centre Shaft Assembly is the ‘Left countershaft’ (1701271-A2V). This is a single, massive, forged component made from high-carbon, case-hardened steel. It is designed to be the primary torque-bearing component in the main box.
Its function is to “counter” the rotation of the input shaft. The input shaft’s gear is in permanent, constant mesh with the “input drive gear” on this FAW Main Box Left-Lower Centre Shaft Assembly. This means that any time the clutch is engaged and the engine is spinning, this countershaft is also spinning.
The shaft itself is precision-machined with multiple “steps,” splines, and bearing journals. The splines are used to mount the various drive gears, while the journals provide a mirror-smooth, ultra-hard surface for the main roller bearings to ride on. A bent or twisted countershaft is a catastrophic failure that requires a full transmission rebuild, making the integrity of this core FAW Main Box Left-Lower Centre Shaft Assembly absolutely critical.
The “logic” of the FAW Main Box Left-Lower Centre Shaft Assembly is embodied in its set of fixed, constant-mesh drive gears. This parts list details the following:
These are the “drive” gears. They are fixed (splined or press-fit) to the ‘Left Countershaft’ and are *always* spinning at the same speed as the shaft. They are in permanent, constant mesh with their corresponding “driven” gears, which spin freely on the main shaft (the “second shaft”).
When the driver selects “3rd gear,” they are actually engaging a clutch (a “synchronizer”) that locks the *freewheeling 3rd gear* to the main shaft. The power flow is then from the input gear, to the FAW Main Box Left-Lower Centre Shaft Assembly, through this ‘3rd gear-countershaft’, to the main shaft, and out to the wheels. These helically-cut gears are designed for quiet, high-torque operation.
The entire FAW Main Box Left-Lower Centre Shaft Assembly is supported at both ends by heavy-duty bearings.
These bearings are protected by “baffles,” which are oil slingers. The ‘Baffle-countershaft rear bearing’ (1701233-A9P) is secured by a ‘Hex head bolt’ (CQ1511235S). This disc spins with the FAW Main Box Left-Lower Centre Shaft Assembly and flings oil *away* from the rear bearing seal, preventing leaks and ensuring a long service life.
Finally, the ‘Circlip-reduction gear’ (1701229-A7G) and ‘Spacer’ (1701247-A7K) are used to lock the ‘Reduction gear’ in its precise location on the shaft. The ‘Woodruff Key’ (1701226-A7G), ‘Flat Key’ (1701228-A7G), and ‘Spring dowel pin’ (Q5280510) are all used to physically lock the various gears to the shaft, ensuring they cannot spin freely and that 100% of the torque from the FAW Main Box Left-Lower Centre Shaft Assembly is transferred.
The following table provides the complete, detailed breakdown of all 14 components identified in the ‘Main Box Left-Lower Centre Shaft Assembly’ diagram for the FAW CA4251P66K24T1A3E5 tractor. This FAW Main Box Left-Lower Centre Shaft Assembly is a key to the transmission’s torque capacity.
| Mark | Part No. | Part Name | Quantity |
|---|---|---|---|
| 1 | CQ1511235S | Hex head bolt | 1 |
| 2 | 1701233-A9P | Baffle-countershaft rear bearing | 1 |
| 3 | 1701215-A2V-C00 | Cylindrical roller bearing | 1 |
| 4 | 1701271-A2V | Left countershaft | 1 |
| 5 | 1701226-A7G | Woodruff key | 1 |
| 6 | Q5280510 | Spring dowel pin | 1 |
| 7 | 1701228-A7G | Flat key | 1 |
| 8 | 1701212-A9K | 3rd gear-countershaft | 1 |
| 9 | 1701213-A9K | 4th gear-countershaft | 1 |
| 10 | 1701214-A9K | 5th gear-countershaft | 1 |
| 11 | 1701247-A7K | Spacer | 1 |
| 12 | 1701217-A7G | Reduction gear-countershaft | 1 |
| 13 | 1701229-A7G | Circlip-reduction gear | 1 |
| 14 | 1701225-A2V-C00 | Cylindrical roller bearing with stop ring | 1 |
The specifications for the FAW Main Box Left-Lower Centre Shaft Assembly are defined by its function as the core, torque-handling gear cluster of the transmission. The entire FAW Main Box Left-Lower Centre Shaft Assembly is a precision-balanced and matched set.
| Vehicle Application | FAW Jiefang CA4251P66K24T1A3E5 6×4 Tractor |
| Component Group | FAW Main Box Left-Lower Centre Shaft Assembly |
| Common Name | Countershaft Assembly / Intermediate Shaft (Left-Lower) |
| Transmission Design | Twin-Countershaft Main Box (This part is one of the two shafts) |
| Main Shaft P/N | 1701271-A2V |
| Gear Set | 3rd (A9K), 4th (A9K), 5th (A9K), Reduction (A7G) |
| Gear Type | Constant-Mesh, Helical-Cut |
| Front Bearing P/N | 1701225-A2V-C00 (Roller Bearing w/ Stop Ring) |
| Rear Bearing P/N | 1701215-A2V-C00 (Cylindrical Roller Bearing) |
| Primary Function | To receive input torque and create multiple gear ratios by driving the main shaft gears. |
FAW parts, including the Cylinder Block Assembly, are packaged with care to ensure safe delivery. Each component is secured in protective materials to prevent damage during transit. The logistics network guarantees timely shipments worldwide, supporting efficient maintenance operations. Below is an image illustrating the standard packaging for FAW truck parts, showcasing the attention to detail in handling and storage.
This packaging approach minimizes the risk of corrosion or impact damage, ensuring that parts like the FAW Cylinder Block Assembly arrive in perfect condition. Customers can rely on FAW’s logistics for consistent quality and reliability.
FAW is one of China’s oldest and largest automotive manufacturers, with registered capital of RMB 35.4 billion yuan and total assets of RMB 457.83 billion yuan.
CHINA FAW GROUP CO., LTD. (short for FAW), formerly China First Automobile Works, can trace its roots back to Jul 15, 1953, when its first assembly plant started to be constructed. FAW is one of China’s oldest and largest automotive manufacturers, with registered capital of RMB 35.4 billion yuan and total assets of RMB 457.83 billion yuan.
China heavy truck sales global “five in a row”, heavy truck sales global “six in a row”, tractor sales for 16 consecutive years absolute leading industry.
