CAT 8J-4918 BEARING CAP

CAT 8J-4918 is a genuine Caterpillar cast iron bearing cap, compatible with the swing gearbox, drive axle differential, and transmission output shaft bearings of Cat 320D/323D excavators and 950H loaders. It is used to seal and position the bearings and withstand axial loads. The following is the original data and does not include replacement parts information.

Core Technical Parameters (Raw Data)

Item Details
Basic Attributes
Model: 8J-4918, Type: Split Bearing Cover (Two-Piece), Material: Gray Cast Iron HT250 (Pearlitic Matrix, Graphite Type A), Surface Treatment: Zinc Phosphate Passivation + Black Epoxy Coating, Weight: 2.35 kg, Operating Temperature: -40℃ to +150℃, Protection Rating: IP65, Compatible Bearing Model: 150-0827/542-1301, Installation Torque: 85-95 N・m, Bolt Specification: M12×1.5 (4 pieces, Grade 8.8)

Key Dimensions
Inner Diameter: 110 mm (Tolerance 0/+0.02 mm), Outer Diameter: 160 mm (Tolerance 0/+0.03 mm), Thickness: 28 mm (Tolerance ±0.1 mm), Sealing Groove Diameter: 120 mm (Width 5 mm, Depth 3 mm), Bolt Hole Center Circle Diameter: 135 mm Bolt hole diameter 12.5 mm (tolerance +0.1/0 mm), locating pin hole diameter 8 mm (2 pieces, tolerance 0/+0.01 mm), locating pin hole center distance 60 mm, split surface flatness ≤0.02 mm, roughness Ra≤1.6 μm

Performance Parameters: Tensile strength ≥250 MPa, yield strength ≥140 MPa, hardness HB 190-240, elastic modulus 110 GPa, Poisson’s ratio 0.27, coefficient of thermal expansion 11.8×10^-6/℃, sealing performance static leakage ≤0.01 mL/min, axial load capacity ≥50 kN, salt spray resistance ≥96 hours, bolt preload 45-50 kN

Structural and Performance Advantages: Split design: The two-piece structure facilitates bearing installation and maintenance, adapts to complex cavities, allows for quick bearing replacement, and reduces downtime.

Gray cast iron material: HT250 possesses excellent rigidity, vibration damping, and wear resistance, making it suitable for heavy-duty vibration conditions. A coating enhances rust resistance.

Integrated sealing groove: Pre-installed O-rings (NBR, 3 mm wire diameter) provide a sealed bearing cavity, preventing dust, moisture, and oil intrusion and extending bearing life.

Locating pin + bolt fixing: Double locating pins ensure coaxial installation, and four 8.8 grade bolts provide stable clamping force to prevent loosening during operation and ensure bearing positioning accuracy.

Installation and maintenance points (raw data)

Installation: Clean the contact surfaces of the bearing cap and bearing housing (free of burrs/oil). Install the O-ring (apply Cat DEO-ULS grease), align the locating pins, and tighten the bolts in three diagonal stages to 85-95 N·m. Check that the sealing surface gap is ≤0.03 mm with no leakage.

Maintenance: Check bolt torque and seal leakage every 1000 hours; replace O-rings every 3000 hours; check bearing cap wear every 12000 hours (wear on the split surface ≤0.05 mm can continue to be used; otherwise, replace).

Troubleshooting: Leakage is often caused by aging O-rings or loose bolts; replace the O-rings and retighten the bolts. Abnormal noise is often caused by bearing cap deformation or out-of-range coaxiality; replace the bearing cap and realign it. Overheating is often caused by overly tight seals; adjust the installation clearance.