FAW Rear Housing Assembly: An Expert Analysis of 22 Core Components

Welcome to this expert analysis of the FAW Rear Housing Assembly (Part No. 1701505-A9P), the critical “auxiliary box” or “range box” for the manual transmission in the FAW Jiefang CA4251P66K24T1A3E5 6×4 diesel semi-trailer tractor.

This FAW Rear Housing Assembly is the foundation of the transmission’s “splitter” or “range” section. It bolts to the back of the main transmission case and contains the crucial gearset that provides the “high” and “low” ranges, effectively doubling the number of available gears (e.g., turning a 6-speed into a 12-speed).

This in-depth guide is an essential resource for professional transmission technicians and parts specialists. We will deconstruct the entire FAW Rear Housing Assembly into its 22 serviceable components, including the main housing, the output shaft bearings, the critical adjustment shims, and the speedometer drive system.

Core Component: The Rear Housing Assembly (1701505-A9P)

The foundation of this entire assembly is the ‘Rear housing with steel wire sleeve set assy’ (1701505-A9P). This is the main structural casing of the FAW Rear Housing Assembly (auxiliary box). It is a massive, precision-machined casting, typically made of aluminum to save weight and dissipate heat.

Its function is to house the entire “range” gearset, which includes the range synchronizer and the “high” and “low” ratio gears. It must hold the auxiliary output shaft and auxiliary counter-shaft in perfect, parallel alignment under thousands of pound-feet of multiplied torque.

The “steel wire sleeve set” designation is a critical, high-quality feature. It means that the high-stress threaded holes in the aluminum FAW Rear Housing Assembly are pre-fitted with “Helicoils” (steel wire thread inserts). This prevents technicians from stripping the soft aluminum threads when tightening the heavy-duty steel bolts, dramatically increasing the component’s service life and durability.

The Critical “Shimming” System: Adjustment Gaskets

The most complex and “logical” part of the FAW Rear Housing Assembly is its shimming system. The parts list details ten different ‘Adjustment gasket-sub box intermediate shaft’ components (Part Nos. 1701526-A9P through 1701537-A9P). These are not standard gaskets; they are **selective shims**.

When a transmission is built, the “end-play” (the amount of fore-and-aft movement) of the counter-shaft is a critical, zero-tolerance specification. If the shaft is too “loose,” the helical gears will “whine” and fail to mesh properly. If it is too “tight,” the bearings will overheat, seize, and be destroyed.

The note “(See 1701526-A9P)” indicates that these parts form a set. A technician assembles the FAW Rear Housing Assembly, measures the end-play with a dial indicator, and then consults a service manual. The manual will instruct them to select *one specific shim* (e.g., 1701528-A9P) from this set. Each shim has a minutely different thickness.

Installing this one, correct shim sets the bearing “preload” to the perfect factory specification. This shimming procedure is the single most important step in rebuilding a FAW Rear Housing Assembly, as it ensures a quiet, reliable, and long-lasting gearbox.

The Output System: Bearings, Caps, and Speedometer

The FAW Rear Housing Assembly provides the final output to the vehicle’s driveshaft. This is supported by the ‘Rear bearing-sub box output shaft’ (1701586-A9P). This is a massive roller bearing that supports the final output shaft, which is subjected to the full, multiplied torque of the selected gear ratio.

This bearing is held in place by the ‘Rear bearing cap-sub box output shaft’ (1701521-A9P), which is a heavy-duty cap that bolts to the rear of the FAW Rear Housing Assembly. This cap not only retains the bearing but also houses the main output shaft oil seal (not pictured), which prevents all the gear oil from leaking out.

This sub-assembly also contains the ‘Speedometer driven shaft assembly’ (1701440-11) and its corresponding ‘Driven gear-speedometer’ (1701446-A9P). This is the mechanical “power take-off” for the speedometer. A plastic gear on the output shaft spins this driven gear, which in turn spins a cable or electronic sensor (via the ‘Speedometer connector’ 1701447-A9P) to provide the vehicle speed to the dashboard. This is a critical data-reporting function of the FAW Rear Housing Assembly.

Service, Support, and Fasteners

The FAW Rear Housing Assembly is designed for service. It includes an ‘Oil filler plug assembly’ (1701765-A2K) and its ‘Gasket’ (1701042-A2K) for filling the auxiliary box with its own separate oil supply. It also features a ‘Cover-sub box shifting oil hole’ (1701517-A9P) for accessing and servicing the range-shifter mechanism.

The entire FAW Rear Housing Assembly is supported and held rigid by the ‘Tension rod flexible cushion assembly’ (1302050-01) and its associated ‘Cushion’ (1302052-01). These “stay rods” connect the heavy transmission to the chassis crossmembers, preventing the entire powertrain from twisting under torque and allowing the ‘Tension bolt’ (1702129-1H) to maintain perfect alignment.

The assembly is held together with a massive number of high-tensile fasteners, including ‘Hex flange bolts’ (Q1841035S, Q1841085S, Q1841035S) and ‘Hex head bolts’ (CQ1500512S). The ‘Spring gaskets’ (Q40308, Q40405) and ‘Hex nuts’ (CQ34008) are critical for ensuring none of these fasteners vibrate loose, which would be catastrophic for the FAW Rear Housing Assembly.

FAW Rear Housing Assembly Parts List

The following table provides the complete, detailed breakdown of all 22 components identified in the ‘Rear Housing Assembly’ (Sub-Box) diagram for the FAW CA4251P66K24T1A3E5 tractor. A rebuild of the FAW Rear Housing Assembly requires careful selection of the correct adjustment gaskets.

Technical Specifications and Assembly Context

The specifications for the FAW Rear Housing Assembly are defined by its function as the structural, precision-machined “sub-box” or “range box”. The entire FAW Rear Housing Assembly is a zero-tolerance component.