3978820 XCMG GR2605 motor grader crankshaft bearing

Technical Parameters

• Model: 3978820
• Type: Lower crankshaft main bearing, STD size
• Material: Steel-backed high-tin aluminum alloy
• Fit engines: 4BT3.9, 6BT5.9, ISBE, ISDE6.7, QSB6.7
• Pair with upper bearing: 3978818
• Structure: Without oil hole or oil groove
• Standard clearance: 0.050–0.102mm
• Surface: Anti-friction coating, good anti-seizure performance

Application Scenarios

Common Faults & Troubleshooting

• Alloy wear and scoring: Caused by contaminated oil, poor lubrication or foreign debris. Symptoms include low oil pressure and engine noise. Replace 3978820 and flush lubrication system.
• Bearing burnout and seizure: Resulted from insufficient oil, overheating, clogged oil passages or long-term overload. Replace complete bearing set and inspect crankshaft journal.
• Excessive clearance and knocking noise: Caused by bearing or journal wear. Measure clearance and replace with STD or corresponding undersize bearings.
• Local spalling and chipping: Due to excessive shock, improper assembly or material fatigue. Install genuine bearings and tighten main caps to standard torque.