Ensemble d'engrenages d'entrée de sous-boîte FAW: Une analyse experte de 5 Composants de base

Bienvenue dans cette analyse technique experte du Ensemble d'engrenages d'entrée de sous-boîte FAW, le complet “saisir” group for the auxiliary “sous-boîte” of the manual transmission in the FAW Jiefang CA4251P66K24T1A3E5 6×4 tracteur semi-remorque diesel.

Le Ensemble d'engrenages d'entrée de sous-boîte FAW is the critical component that receives 100% of the power from the transmission’s main box and transfers it into the auxiliary box (the range/splitter section). This mechanism is what turns a 6-speed main box into a 12-speed transmission, providing the high and low ranges necessary for a heavy-duty tractor.

This guide is an essential resource for professional transmission rebuilders and parts specialists. Nous déconstruirons l'ensemble Ensemble d'engrenages d'entrée de sous-boîte FAW dans son 5 composants réparables, including the main ‘Input Gear’ (1701431-A8P), its critical ‘Deep groove ball bearing’ (6218 NR/YA7), and the associated locating plates and circlips.

Understanding the “Sub-Box” Logique

To understand the Ensemble d'engrenages d'entrée de sous-boîte FAW, one must first understand the “sous-boîte,” also known as the auxiliary transmission or range box. Heavy-duty transmissions like the one in this FAW tractor are often “6+1” ou “8+1” speed main boxes. To achieve the 12, 16, ou 18 speeds needed for heavy hauling, this main box is bolted to a 2-speed “sub-box.”

This sub-box has two settings: “Gamme basse” (un réducteur) et “Haut de gamme” (a direct drive). The driver shifts through the main box pattern (Par exemple, 1-6) while in “Faible,” then flips a switch. This engages the sub-box synchronizer, shifting it from Low to High. The driver then shifts through the *same* 1-6 pattern again, which now function as gears 7-12.

Le Ensemble d'engrenages d'entrée de sous-boîte FAW (1701431-A8P) est le “porte d'entrée” à cette sous-boîte. It is in constant mesh with the output gear of the main transmission, and it is the component that all the synchronizers and gears inside the sub-box receive their power from. Donc, this single gear and shaft assembly handles the full, multiplied torque of the engine in *every single gear*. Its durability is absolutely paramount, as a failure here renders the entire transmission inoperable. Le Ensemble d'engrenages d'entrée de sous-boîte FAW is a zero-failure-tolerance component.

Composant principal: The Input Gear (1701431-A8P)

Le coeur du Ensemble d'engrenages d'entrée de sous-boîte FAW is the ‘Input gear-sub box’ (1701431-A8P). C'est un énorme, helically-cut gear that is permanently integrated with its shaft. This component is forged from a single billet of high-manganese, acier cémenté (like 18CrNiMo7-6) to provide an incredibly tough inner core that resists shock-load and an glass-hard outer surface that resists wear.

L'hélicoïdal (incliné) cut of the gear teeth is a critical design choice for the Ensemble d'engrenages d'entrée de sous-boîte FAW. This design allows the gear teeth to engage gradually, ce qui est nettement plus silencieux que “éperon” (coupe droite) engrenages. Plus important encore, the helical cut allows multiple teeth to be in mesh at the same time, spreading the immense torque load over a much larger surface area.

A chipped tooth on this single gear, often from a bad shift or driveline shock, est un échec catastrophique. It would send hardened steel fragments throughout the entire auxiliary transmission, destroying all other gears and bearings. Cela rend le Ensemble d'engrenages d'entrée de sous-boîte FAW‘s gear one of the most durable components in the driveline.

Le roulement principal: Roueur à billes de rainure profonde (6218 NR/YA7)

The ‘Input gear-sub box’ shaft is supported by the ‘Deep groove ball bearing’ (6218 NR/YA7). This is the single most important component for the alignment and low-friction rotation of the entire Ensemble d'engrenages d'entrée de sous-boîte FAW.

Le “6218” designation indicates this is a large, heavy-duty bearing with a 90mm (3.54 dans) bore. A ball bearing is used here because it is exceptionally good at handling both **Radial Loads** (the separating force from the helical gears) and **Axial Loads** (le “poussée” or push/pull force) dans les deux sens.

Le “NR/YA7” suffix is the most critical part:

• **N:** Indicates a “snap ring groove” is machined into the *outer* race of the bearing.
• **R.:** Indicates that the “anneau élastique” (or circlip) *is included* with the bearing.

This snap ring is the “logique” of the mounting system. The bearing is pressed onto the Ensemble d'engrenages d'entrée de sous-boîte FAW arbre. The entire assembly is then inserted into its precision bore in the transmission case. The snap ring (1701358-A7G) then fits into this “N” rainure, locking the *outer* race of the bearing to the case. This single ring prevents the entire Ensemble d'engrenages d'entrée de sous-boîte FAW from moving fore or aft.

A failure of this bearing is a primary cause of transmission failure. It is often first heard as a high-pitched “gémissement” ou “gronder” that is present in all gears and is tied to vehicle speed. If this bearing seizes or collapses, le Ensemble d'engrenages d'entrée de sous-boîte FAW will be destroyed.

The Alignment System: Circlips and Locating Plate

The final three components of the Ensemble d'engrenages d'entrée de sous-boîte FAW are dedicated to precision alignment and “shimming” (setting the correct end-play).

**1. ‘Circlip-input gear bearing’ (1701357-A7G):** This is a large snap ring, or circlip. Its function is to lock the *inner* race of the 6218 bearing onto the ‘Input gear-sub box’ arbre. This prevents the shaft from sliding *out* of the bearing.

**2. ‘Locating ring-circlip’ (1701358-A7G):** This is the snap ring that fits into the “NR” groove on the *outer* race of the 6218 palier. It locks the *outer* race of the bearing into the transmission case. These two circlips, one on the inner race and one on the outer, create a “fermé” assembly that is fixed to both the shaft and the case.

**3. ‘Locating plate-input gear bearing’ (1701432-A9K):** C'est un “baffle” ou “capuchon” that is often bolted over the bearing on one side. It serves two functions: it acts as a final, redundant “arrêt” to prevent the bearing from moving, and it acts as an oil “slinger” or shield, protecting the bearing’s seal from direct splash and helping to channel lubrication into the bearing.

Ensemble, ces 5 components form the complete, utilisable Ensemble d'engrenages d'entrée de sous-boîte FAW. A transmission rebuilder must replace these circlips, as re-using a “à ressort” ou “fatigued” circlip is a major risk. If one fails and falls into the rotating gearset, it will destroy the entire transmission. Le Ensemble d'engrenages d'entrée de sous-boîte FAW relies on these small parts.

FAW Sub-Box Input Gear Assembly Parts List

Le tableau suivant fournit l'intégralité, ventilation détaillée de tous 5 components identified in the ‘Sub-Box Input Gear Assembly’ schéma du tracteur FAW CA4251P66K24T1A3E5. A full rebuild of the Ensemble d'engrenages d'entrée de sous-boîte FAW requires these precision-matched parts.

Spécifications techniques et contexte d'assemblage

Les spécifications pour le Ensemble d'engrenages d'entrée de sous-boîte FAW are defined by its function as the primary, constant-mesh input drive for the transmission’s auxiliary (gamme) section. Le Ensemble d'engrenages d'entrée de sous-boîte FAW est un ensemble adapté avec précision.