FAW Internal Control Components: Inside The 32 Critical Parts That Shift Your Transmission

Welcome to this critical technical guide on the FAW Internal Control Components, the complete “shift logic” assembly for the manual transmission in the FAW Jiefang CA4251P66K24T1A3E5 6×4 diesel semi-trailer tractor. This system is the “brain” that translates the driver’s hand movement into mechanical gear selection.

The FAW Internal Control Components are not the gears themselves, but the entire “top-cover” assembly of forks, rails, and interlocks that physically move the synchronizer sleeves. When the driver moves the gear stick, they are moving this assembly, which in turn selects the desired gear.

This in-depth guide is an essential resource for professional transmission technicians. We will deconstruct the entire FAW Internal Control Components system into its 32 serviceable parts, including the shift forks for every gear, the shift rails (shafts) they ride on, and the critical interlock and detent mechanisms that ensure safe, precise shifting.

Core Components: The Shift Fork System

The “muscle” of the FAW Internal Control Components is the set of shift forks. These are heavy-duty, forged steel “yokes” that ride in the grooves of the synchronizer sliding sleeves (as detailed in assembly 145). This parts list details the complete set:

• ‘Fork-1st, 2nd gear’ (1702031-A9P)
• ‘Fork-3rd, 4th gear’ (1702041-A9P & 1702048-A9P)
• ‘Fork-5th, 6th gear’ (1702051-A9P, 1702053-A9P, 1702052-A9P)
• ‘Fork-reverse gear’ (1702067-A9P)

When the driver selects a gear, the gear lever (via the ‘Shaft-shift mechanism’ 1702078-A1K) selects one of these forks. The ‘Shaft-shift fork support’ (1702073-A9P) then slides this fork “forward” or “backward.” This fork, in turn, slides the synchronizer sleeve, which engages the gear. The ‘Fork-reverse gear’, for example, is responsible for moving the reverse idler gear into its mesh position.

The “pads” or “tines” of these forks are the primary wear item. They are in constant contact with the spinning synchronizer sleeve. Over millions of shifts, these pads can wear down. Worn shift forks are a primary cause of a “sloppy” shifter, grinding gears, or the transmission “popping out” of gear under load. These forks are the most critical moving parts of the FAW Internal Control Components.

The “Logic”: Interlock System (1702081-A9P)

The most important “logic” of the FAW Internal Control Components is the **interlock system**. It is a critical safety mechanism that makes it physically impossible to select two different gears at the same time (which would instantly lock and destroy the transmission).

This “logic gate” is created by a clever mechanical system of plates, balls, and pins:

• ‘Interlock plate’ (1702081-A9P, 1702082-A9P, 1702083-A9P, 1702089-A9P)
• ‘Steel ball’ (Q967165) – 4 units
• ‘Bushing-interlock plate’ (1702084-A9P)

This is how it works: The shift shafts (rails) run parallel to each other. Between them are channels containing the ‘Steel balls’. When all shafts are in neutral, the balls can move freely. However, as soon as one shift shaft (e.g., the 1st/2nd gear shaft) is moved, its ‘Interlock plate’ pushes one of the ‘Steel balls’ *sideways* into a groove on the *other* shift shafts (e.g., the 3rd/4th shaft). This “rogue” ball, now out of its channel, physically blocks the other shafts from moving.

This ensures that only one shift shaft, and therefore only one shift fork, can be moved out of its neutral position at any given time. This simple, robust mechanical “logic” is a core feature of the FAW Internal Control Components. A worn ‘Interlock plate’ or a missing ‘Steel ball’ is a critical failure that could allow a double-gear engagement.

The “Detent” System (Self-Locking)

The “detent” system provides the “feel” of the gear shift and prevents the transmission from vibrating out of gear. This part of the FAW Internal Control Components is comprised of the ‘Cover-self-locking mechanism’ (1702227-A9P), its ‘Gasket’ (1702228-A9P), and the four ‘Self-locking spring’ (1702061AA4P) units.

Each shift shaft has three “detent” grooves machined into it: one for Neutral, one for the “forward” gear (e.g., 3rd), and one for the “backward” gear (e.g., 4th). The ‘Self-locking spring’ pushes a small steel ball or “plunger” (often part of the 1702061AA4P assembly) into this groove.

When the driver shifts, they must apply enough force to overcome this spring, causing the ball to “pop out” of the neutral groove and “pop into” the 3rd gear groove. This is what creates the “click” or “thunk” that confirms the gear is fully engaged. It also serves as a critical locking mechanism, as the spring’s force holds the shaft in place, preventing engine vibration from “walking” the fork and causing the transmission to pop out of gear. A weak or broken ‘Self-locking spring’ is the primary cause of a transmission that will not stay in gear. This detent system is a key “logic” of the FAW Internal Control Components.

Limiters and Electronic Switches

The FAW Internal Control Components also include physical “stops” and electronic “sensors.” The ‘Limit stop block-shift rail’ (1702092-A9P) and ‘Limit stop block-reverse gear’ (1702068-A9P) are the final “hard stops” that prevent the shift forks from over-traveling. They are secured with ‘Flat head dowel pin’ (1702097-A9P) units.

The most important electronic part is the ‘Stop light switch assembly’ (3729100-71A). This is the **reverse light switch**. It is a simple plunger-style switch. When the driver moves the ‘Fork-reverse gear’ (1702067-A9P), the shift shaft presses this plunger, which completes an electrical circuit, turning on the truck’s white reverse lights and sounding the backup alarm. This switch is a critical safety component of the FAW Internal Control Components.

Finally, the ‘Shaft-shift rocker arm’ (1702074-A9P) and its ‘Support’ (1702072-A9K) form the pivot that transfers the driver’s shift-lever motion to the main shift shafts. The entire FAW Internal Control Components assembly is a complex mechanical computer.

FAW Internal Control Components Parts List

The following table provides the complete, detailed breakdown of all 32 components identified in the ‘Internal Control Components’ (Shifter Assembly) diagram for the FAW CA4251P66K24T1A3E5 tractor. This FAW Internal Control Components system is the “logic” of the gearbox.

Technical Specifications and Assembly Context

The specifications for the FAW Internal Control Components are defined by its function as the transmission’s mechanical “logic” board. This FAW Internal Control Components system is responsible for all gear selection.