CAT 077-7776 BUSHING

CAT 077-7776 is a Caterpillar genuine straight-tube steel bushing (pure original factory information, no additional description), used for shaft and bore mating in articulation, transmission, or hydraulic systems of engineering machinery. It provides wear resistance, guidance, and vibration damping, and is suitable for heavy-duty vibration conditions in Cat® applications…

Core Parameters and Information

Project Details
Part Model: CAT 077-7776 (0777776) Sleeve Bushing

Structure Type: Straight cylindrical without flange, inner wall with spiral oil groove + axial oil passage, chamfered ends 1×45°, surface hard chrome plated for corrosion protection

Material: 42CrMo alloy steel, quenching hardness HRC 58-62, surface hard chrome plated layer thickness 0.02-0.03 mm, salt spray test ≥96 h, density 7.85 g/cm³

Key Dimensions: Inner diameter 100 mm, outer diameter 115 mm, length 80 mm, oil groove depth 0.5 mm, oil passage diameter 2 mm, wall thickness 7.5 mm, chamfer 1×45°

Performance Parameters: Radial load ≥50 kN, coefficient of friction ≤0.08 (lubricated state), wear layer hardness HV≥800, operating temperature -40℃ to + 120℃, coefficient of thermal expansion 11.5×10^-6/℃
Compatibility Standard: Conforms to CAT bushing specifications, dimensional tolerance GB/T 15481-7 grade, surface roughness Ra≤0.8 μm, roundness≤0.01 mm
Match Relationship: Interference fit into the seat hole; clearance fit between shaft and bushing (clearance 0.03-0.05 mm), forced lubrication through oil grooves.
Compatible Machines and Applications:
Compatible Parts: Matched with pins, bushings, and spherical bearings; used in excavator boom/stick hinge pins, loader rocker arm pins, bulldozer blade connecting pins, etc., to reduce wear between shaft and seat hole and absorb impact vibration.

Compatible Equipment: CAT 320/323/330 series excavators, 972/980 series loaders, D6/D7 series bulldozers, and other construction machinery.

Matching Installation: One bushing is provided at each hinge point. After pressing into the seat hole, it will have a clearance fit with the pin. Lubrication is achieved via grease injection; it is recommended to replenish grease every 500 hours.

Installation and Maintenance Points: Clean the bushing and seat hole, checking for deformation, cracks, and rust. Measure the outer diameter and the inner diameter of the seat hole, ensuring an interference fit of 0.05-0.08 mm (cold fitting) or 0.10-0.12 mm (hot fitting).

For cold fitting, press in smoothly using a press. For hot fitting, heat the bushing to 120-150℃ and then quickly press it into the seat hole. After cooling, a reliable interference fit should be formed, ensuring no loosening.

After installation, check that the inner hole roundness is ≤0.01 mm, the surface is free of scratches, the clearance with the pin is 0.03-0.05 mm, rotation is smooth without jamming, and there are no abnormal noises.

Maintenance: Check lubrication and wear every 500 hours. Replace the bushing when the wear on the inner diameter is >0.1 mm or when peeling/cracks appear on the surface. Use a special puller for disassembly. Do not knock hard to avoid damaging the seat hole.