3978822 XCMG GR2605 motor grader crankshaft thrust bearing

Technical Parameters

• Part No.：3978822 (C3978822), Thrust Bearing Half
• Brand：Cummins / DCEC
• Type：Crankshaft Thrust Washer, STD Size
• Material：Steel-backed Al-Sn alloy (duplex coated)
• Structure：Semi-circular, dual thrust faces, oil distribution grooves
• Size：Fits φ76.2mm main journal, standard thickness 2.5mm
• Clearance：Standard endplay 0.05–0.25mm, wear limit ≤0.35mm
• Fit Engines：4BT3.9, 6BT5.9, ISBE, ISDE6.7, QSB6.7
• Qty：2 per engine (1 set)
• Pair：3978824 (lower/thicker thrust)
• Cross：3906230, 3927772

Application Scenarios

• Engines：4BT3.9, 6BT5.9, ISBE, ISDE, QSB6.7, B5.9
• Vehicles：Dongfeng Kinland, Tianjin, 153, Duolika
• Machinery：1–3.5T loaders, excavators, bulldozers, rollers
• Gensets：50–150kW diesel generators
• Location：Center main saddle (4th journal), mates with crank thrust faces
• Function：Limit crank endplay, absorb axial thrust, maintain alignment

Common Faults & Troubleshooting

1. Wear & Excessive Endplay

• Cause：Poor lubrication, contamination, overload, clutch thrust issues
• Symptom：Crankshaft movement, shift shock, noise, endplay >0.35mm
• Fix：Replace 3978822 set; clean oil galleries; check clutch release bearing

2. Alloy Spalling & Burnout

• Cause：Heat, lubrication failure, fatigue, debris, axial shock
• Symptom：Flaking, scoring, crank wear, oil contamination
• Fix：Install genuine 3978822; inspect crank thrust faces; set proper clearance

3. Reversed Installation & Dry Friction

• Cause：Incorrect orientation, alloy/steel side mix-up
• Symptom：Rapid wear, noise, crank thrust face damage
• Fix：Install with alloy side to crank; verify 3978822 orientation