Caterpillar S4K Crankshaft 4W-3989 for E120B Excavator

Uncompromising Job-Site Durability: Forged Caterpillar S4K Crankshafts

Industrial Diesel Engine Components require resilience to withstand the harsh duty cycles of earthmoving, and Ruich Value delivers high-strength aftermarket solutions for your Caterpillar fleet. We specialize in sourcing and manufacturing critical internal components that meet the rigorous standards of heavy construction machinery.

This forged steel crankshaft, referencing OEM 4W-3989, is engineered specifically for the Caterpillar S4K engine series found in classic excavators like the E110B and E120B. Addressing the common industry pain points of fatigue cracking and journal wear, our crankshafts feature induction-hardened fillets and journals. This metallurgical enhancement significantly improves torsional strength, ensuring your equipment stays operational on the job site. Whether you are rebuilding a loader or an excavator, our S4K crankshaft restores the factory-level performance and reliability synonymous with the Caterpillar brand.

Technical Specifications for CAT S4K Forged Crankshaft

Technician’s Note: Installation & Inspection

Technician’s Note: The CAT S4K engine shares design architecture with the Mitsubishi 4D31. When installing this crankshaft, it is critical to verify the crankshaft end-play (thrust clearance) and ensure the main bearing caps are torqued to specification in the correct sequence. Neglecting end-play checks can lead to rapid thrust washer failure and block damage.

Verified CAT S4K Engine & Equipment Applications

Why Source Heavy Duty Parts From Ruich Value?

• Forged Integrity: We strictly supply forged steel crankshafts for the S4K application to handle the high-torque stress of excavation, avoiding the risks associated with cast iron alternatives.
• Precise Grinding: Journals are CNC ground to OEM tolerances, ensuring perfect oil film thickness and compatibility with standard or undersize bearing sets.
• Ready Inventory: We understand that machine downtime costs money. We maintain stock of popular numbers like 4W-3989 for rapid dispatch to job sites worldwide.
• Quality Assurance: Every unit undergoes magnetic particle inspection (MPI) to detect any microscopic cracks or forging defects before packaging.

Complete Caterpillar Crankshaft Catalog

Ruich Value offers a comprehensive range of Industrial Diesel Engine Components to keep your heavy machinery running. From the compact S4K to the massive C15, our catalog covers the essential power components for your rebuild.

Category coverage: Our inventory includes crankshafts for CAT 3306, 3304, S6K, 3066, C6.4, C7, and C9 series engines.

View all specs in our Industrial Diesel Engine Components Crankshaft Catalog.

Or explore the complete Caterpillar Industrial Diesel Engine Components Range

Technical FAQ: Caterpillar S4K Crankshaft

Q: Is this crankshaft compatible with Mitsubishi 4D31 engines?

A: Yes, the Caterpillar S4K engine is based on the Mitsubishi 4D31 architecture. The Ruich Value 4W-3989 crankshaft is generally interchangeable with the Mitsubishi 4D31 crankshaft found in Fuso Canter trucks and Kato excavators. However, always confirm the gear keyway and flange bolt pattern with our team before ordering.

Q: Does the crankshaft include the timing gear?

A: Our standard supply for the S4K crankshaft is the bare shaft only. The timing gear is a press-fit component that is usually transferred from your original unit or purchased separately. If you require a pre-installed gear, please specify this in your quote request.

Q: What material is used for this S4K crankshaft?

A: This unit is manufactured from Forged Steel. While some cheaper market options use cast iron, Ruich Value prioritizes forged steel for excavator applications to resist the high bending and torsional fatigue encountered during heavy digging.

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Customized/billet crankshaft development based on drawings or samples is also possible.

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