CAT 4N-3887 0.652\ Inner Diameter Retainer Ring

CAT 4N-3887 is a Caterpillar governor retaining ring (stop ring/retaining ring), used inside the engine governor assembly to axially position governor gears, bearings or pistons and other parts to prevent displacement during operation. It is compatible with heavy-duty diesel engines such as Cat 3406 and C15 and is a key small hardware component to ensure stable operation of the governor. The following is structured technical and application information:

Core Technical Parameters

Item Details
Basic Attributes
Model 4N-3887, type is external snap-fit ​​shaft elastic retaining ring (E-shaped retaining ring), material is 65Mn spring steel (zinc-plated and passivated for corrosion resistance), hardness HRC42-48, single weight approximately 0.02 kg, applicable temperature -40℃ to +150℃, elastic deformation ≤0.5 mm, applicable speed ≤5000 rpm, installation method is snap-fit ​​clamp embedded in shaft groove for fixation

Key Dimensions
Inner diameter 38 mm (tolerance 0 to -0.10 mm), outer diameter 45 mm (tolerance +0.05 to +0.15 mm), thickness 1.2 mm (tolerance ±0.05 mm), opening width 5 mm, groove diameter fits 38 mm (groove width 1.3 mm, tolerance +0.05 to +0.10 mm), chamfer 0.3 mm×45°, radial elastic force ≥50 N, axial load capacity ≥1200 N, matching shaft diameter 38 mm (clearance fit recommended)

Compatible Models and Applications: Compatible with Cat 3406, 3408, 3412, C15, and C18 heavy-duty diesel engines. Installed in the positioning groove of the governor drive shaft, governor gear shaft, or flyweight shaft to fix the governor bearing, flyweight assembly, or gear, preventing axial movement. Matching parts include snap ring grooves and shaft retainer ring installation clamps. Suitable for operating conditions with speeds ≤3000 rpm.

Performance Parameters: Surface treatment is color zinc passivation (salt spray test ≥48 hours), breaking strength ≥800 MPa, elastic limit ≥600 MPa, repeated disassembly and assembly cycles ≥5 times, working pressure ≤1 MPa (static axial load), no sealing function, only serves a positioning purpose.

Structural and Performance Advantages:
Precise Positioning: The compact elastic retainer ring structure provides stable axial positioning after embedding in the shaft groove, preventing displacement of internal governor parts and ensuring speed regulation accuracy. Easy Installation: Utilizing a standard E-shaped structure, it can be quickly installed and removed using ordinary snap ring pliers, requiring no special tooling and improving maintenance efficiency.

Low Cost: The unit price of the parts is low (original parts approximately 30-50 RMB/piece, aftermarket parts approximately 10-20 RMB/piece), but it is crucial for the stable operation of the governor assembly, making it a cost-effective wear part.

Good Corrosion Resistance: The galvanized passivation surface treatment effectively prevents rust, making it suitable for the humid and dusty environment inside the engine compartment.

Installation and Maintenance Points: Before installation, clean the shaft groove and retaining ring, checking for burrs and rust on the groove walls, and ensuring the retaining ring is free from deformation and cracks. Use snap ring pliers to pry open the retaining ring, align it with the shaft groove, and slowly release it, ensuring the retaining ring is fully embedded in the groove, fitting snugly against the shaft shoulder, with axial movement ≤0.05 mm.

Every 2000 hours of engine maintenance, check the elasticity and surface condition of the retaining ring. If deformation, breakage, or severe corrosion is found, replace it immediately.

When replacing parts, original parts should be selected first to ensure material elasticity and dimensional accuracy, and to avoid positioning failure due to insufficient elasticity, which could lead to speed controller malfunction.