Crankshaft

Crankshaft Components for Cummins 4BT Engines

The Cummins 4BT engine is a legendary workhorse across industrial, marine, agricultural, and construction equipment applications. Known for its compact design and long service life, the 4BT relies on a robust internal rotating assembly to deliver reliable torque under pressure. At the heart of this assembly is the crankshaft—a precision-forged component responsible for translating piston motion into rotational energy.

If you're rebuilding your 4BT or replacing worn-out rotating components, this section contains everything you need to restore the crankshaft system to OEM-level performance, including the crankshaft itself, crankshaft bearings, front and rear oil seals, vibration dampers, and supporting hardware.

New Crankshaft for Cummins 4BT

Premium-Grade Replacement Crankshaft

When your existing crankshaft is damaged from wear, scoring, heat fatigue, or bearing failure, a full replacement is often the only solution. Diesel Pro Power offers a new crankshaft engineered specifically for the Cummins 4BT.

• Engine Compatibility: Cummins 4BT 3.9L

• Design: Four-cylinder inline forged crankshaft

• Condition: Brand new, not remanufactured

• Construction: Heat-treated and precision-ground for OEM fitment

• Benefit: Delivers stable oil pressure, reduces vibration, restores proper timing dynamics

Every crankshaft ships pre-balanced and ready to install, minimizing time in the machine shop and ensuring long-term durability in high-load environments like marine generators or industrial power units.

Crankshaft Bearings for Cummins 4BT

The crankshaft bearings are critical to the longevity of your 4BT engine. These bearing shells support the crankshaft at the main journals, maintaining oil film thickness and protecting against metal-on-metal contact.

Standard Bearing Shell Set – 4BT

• Use Case: For engines with unmodified, standard-size crankshafts

• Configuration: Complete upper and lower bearing shells for all main journals

• Fitment: Drop-in ready for standard journal 4BT crankshafts

• Construction: Tri-metal design with corrosion-resistant overlay

• Packaging: Full set for the crankshaft main line

0.25 mm Oversize Crankshaft Bearings

• Use Case: For crankshafts that have been ground to 0.25 mm oversize

• Why It Matters: Helps restore correct oil clearances after crankshaft machining

• Includes: Complete main bearing set with 0.25 mm oversize shells

• Durability: Designed to meet or exceed Cummins original bearing load specs

0.50 mm Oversize Crankshaft Bearings

• Use Case: For engines with significant journal wear, machined to 0.50 mm oversize

• Benefit: Extends the life of crankshafts that would otherwise be scrapped

• Configuration: Upper and lower shell bearings for all main journals

• Precision: Manufactured with tight tolerances for oil film integrity

All bearing sets are pre-matched and designed to maintain correct thrust and axial loading on the 4BT crankshaft, ensuring your rebuild holds oil pressure and rotational alignment under full load.

Crankshaft Seal Kits for Cummins 4BT

Crankshaft oil seals prevent engine oil from leaking past the front and rear ends of the crankshaft. Over time, these seals harden, shrink, or wear against the rotating shaft—especially in engines operating in extreme temperature or duty cycles.

Front Crankshaft Seal Kit

• Includes: Crankshaft seal + dust shield

• Installation Location: Front timing cover

• Fitment: Direct replacement for Cummins 4BT front main seal

• Purpose: Keeps oil from leaking near the crank pulley

• Note: Ideal for standard front housing configurations

Front Crankshaft Seal Kit with Sleeve

• Includes: Crankshaft seal and standard sleeve

• Why Use It: If your crankshaft's seal surface is worn or grooved, the sleeve restores a smooth sealing surface

• Benefit: Prevents oil leaks from forming even on older crankshafts

• Recommended For: Engines that experienced prior front main seal leakage

Rear Crankshaft Seal Kit

• Includes: Rear main seal and installation sleeve

• Installation Location: At the back of the crankshaft near the flywheel

• Fitment: Designed for 4BT engines with dry clutch housings

• Importance: Prevents oil contamination in the flywheel area, which can lead to slipping or failure of clutches and flywheel housings

These seals are constructed from high-durability elastomers and are engineered to resist heat, vibration, and chemical degradation—ideal for the harsh conditions in which 4BT engines operate.

Vibration Dampers for Cummins 4BT

A vibration damper (also called a harmonic balancer) is mounted on the front of the crankshaft and plays a critical role in reducing engine vibration and crankshaft flexing. Without it, the 4BT engine would be far more prone to torsional fatigue and failure under continuous load.

4BT Vibration Damper – 8.23” Outside Diameter

• Bolt Configuration: 4 bolt holes

• Size: 8.23 inches OD

• Material: Steel housing with elastomer inner ring

• Purpose: Absorbs torsional vibration and reduces harmonic resonance

• Fitment: Optimized for naturally aspirated and light-duty 4BT configurations

4BT Vibration Damper – 9.7” Outside Diameter

• Bolt Configuration: 4 bolt holes

• Size: 9.7 inches OD

• Application: Designed for 4BT engines running at higher RPM or under continuous load

• Benefit: Greater rotational mass improves dampening performance

Replacing the vibration damper during a crankshaft service is strongly recommended, especially in high-hour or marine-use 4BT engines where internal balance and vibration control are essential to long-term operation.

Related Components: Expansion Plug Kit for Cummins 4BT Blocks

During crankshaft and lower-end service, many technicians also choose to replace expansion plugs (also called freeze plugs or core plugs). These plugs prevent coolant leaks and corrosion inside the engine block water passages.

• Application: Cummins 4BT 3.9L engine block

• Style: Storm-type block plug kit

• Contents: Full kit of replacement plugs for the crankcase and water jacket

• Purpose: Ensures no coolant leakage or internal rusting near crankshaft areas

Why Buy Cummins 4BT Crankshaft Parts from Diesel Pro Power?

With more than 40,000 satisfied customers worldwide, Diesel Pro Power is a trusted name in Cummins 4BT engine parts. Every crankshaft component on this page is:

• Engineered for exact fitment on the 4BT engine

• In stock and ready to ship from our U.S.-based warehouse

• Backed by our knowledgeable support team

• Compatible with both marine and industrial applications

• Offered with clearly labeled options (standard, 0.25 mm, 0.50 mm, etc.) for easy selection