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Cummins 4B Engine Parts - Crankshaft Section

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Crankshaft and Rotating Assembly Components for Cummins 4B Engines

The Cummins 4B engine, a naturally aspirated 4-cylinder powerhouse from the legendary B-Series family, is known for its robust construction and long service life. Whether you're overhauling a marine, industrial, or generator-spec application, the crankshaft is one of the most critical components in your 4B engine’s bottom-end assembly. This section provides a complete breakdown of available new crankshafts, crankshaft bearings (shell sets), crankshaft seals, vibration dampers, and related hardware—everything needed to ensure reliable performance from your Cummins 4B rotating assembly.

New Crankshaft for Cummins 4B, 4BT, and 4BTA Engines

A properly machined and balanced crankshaft is at the heart of your Cummins 4B engine’s internal operation. Diesel Pro Power offers a high-quality new crankshaft suitable for use in Cummins 4B, 4BT, and 4BTA engines, ensuring optimal fit and performance without the risk associated with used or reconditioned units.

Key Features:

  • Compatible with 4B 3.9L naturally aspirated and turbocharged variants

  • Precision-machined for factory-spec oil clearances and journal diameters

  • Made from hardened steel for superior fatigue resistance

  • Balanced for reduced vibration and smoother operation

This new crankshaft is ideal for customers seeking OE-level quality without paying dealership prices. It is backed by Diesel Pro Power’s dedication to quality and comes ready for immediate installation.

Crankshaft Bearing Sets (Shell Sets)

Crankshaft bearings—commonly referred to as main bearings or shell sets—are essential for supporting crankshaft rotation within the engine block. At Diesel Pro Power, we carry standard and oversize crankshaft shell sets to match various rebuild scenarios. Proper bearing selection is critical for establishing correct oil film thickness and maintaining oil pressure.

Standard Size Crankshaft Shell Set

This standard-size bearing set is designed for engines with stock crankshafts or those that have been polished but not machined undersize. Each set includes upper and lower main bearings for a complete installation.

Oversize Crankshaft Shell Sets – 0.25 mm and 0.50 mm

Oversize bearings are used when the crankshaft journals have been reground to restore roundness after wear. We offer:

All bearing sets are designed for long-lasting durability with proper oil groove placement and anti-friction coatings to reduce wear during startup and full-load operation.

Front and Rear Crankshaft Seal Kits

Seals located at the front and rear of the crankshaft prevent oil leakage from the engine’s main housings. We offer both front and rear crankshaft seal kits, each designed to match Cummins 4B, 4BT, and 4BTA engines. These kits are engineered for reliability in high-vibration diesel environments.

Front Crankshaft Seal Kits:

We carry two versions:

  • Front Seal with Dust Shield: This economical kit includes the seal and protective dust shield, ideal for standard maintenance.

  • Front Seal with Sleeve: This upgraded version includes a replacement wear sleeve, ensuring a proper sealing surface even if the original crankshaft has minor scoring.

Rear Crankshaft Seal Kit:

Our rear seal kit includes the seal and wear sleeve for engines with dry clutch housings, offering reliable sealing under thermal cycling and high torque.

All seals are made from advanced elastomer compounds for superior heat and oil resistance.

Vibration Dampers for Cummins B-Series Engines

The vibration damper, also called the harmonic balancer, helps neutralize torsional vibrations generated by the crankshaft. Replacing a worn or failed damper can reduce noise, extend bearing life, and protect the crankshaft from stress fractures. Diesel Pro Power offers two vibration damper options for the Cummins 4B and compatible B-Series engines:

Available Options:

Both dampers are direct-fit replacements with factory-balanced designs for optimal performance.

Crankshaft-Related Hardware and Accessories

A complete crankshaft rebuild often includes more than just the crankshaft and bearings. Supporting components such as gaskets, plugs, and vibration control systems ensure a proper seal and long-term reliability.

Expansion Plug Kit for Engine Block

This kit includes all required freeze plugs and block-off plugs for the 4B 3.9L engine. It’s especially critical when rebuilding a long-block or replacing a crankshaft, as worn or rusted plugs can compromise coolant containment and lead to leaks.

Crankshaft Installation Guidelines

When replacing the crankshaft in your Cummins 4B engine, it’s important to follow industry best practices to ensure long-term performance. Below are key steps and tips that mechanics and rebuilders follow:

1. Inspect and Clean the Engine Block

Thoroughly inspect main bearing saddles for wear, scoring, or deformation. Clean oil passages and remove all gasket debris. Check for cracks using magnetic particle inspection or dye penetrant if needed.

2. Measure Bearing Clearances

Use plastigage or micrometer measurements to verify clearance between the crankshaft journals and bearing shells. Proper clearance is essential to ensure sufficient oil film thickness for bearing protection.

3. Lubricate and Install

Apply assembly lube or engine oil to journals and bearings before setting the crankshaft into place. Always torque main bearing caps to manufacturer specifications in the correct sequence.

4. Check Endplay

Use a dial indicator to measure crankshaft endplay. Excess endplay can lead to premature thrust bearing failure, while tight endplay may cause binding during operation.

5. Align Front and Rear Seals

Align front and rear crankshaft seals carefully, and use the included wear sleeve (if applicable) to avoid leaks. Seals must be seated evenly and should not be over-lubricated.

Common Signs of Crankshaft or Bearing Wear in Cummins 4B Engines

Routine inspections of your 4B engine should include monitoring for signs of crankshaft wear. Ignoring early symptoms can result in catastrophic failure.

Warning Signs Include:

  • Knocking noise from the engine block

  • Metal shavings in the oil

  • Low oil pressure at idle

  • Oil leaks near the rear or front main seal

  • Excessive vibration or belt misalignment

Why Choose Diesel Pro Power for Your 4B Crankshaft Components?

With over 40,000 satisfied customers worldwide, Diesel Pro Power is a trusted source for Cummins 4B engine components. Our crankshaft and rotating assembly parts are:

  • Backed by technical expertise and dedicated customer service

  • Shipped quickly from stock with fast turnaround

  • Available for immediate purchase through our online platform

Each product listing includes technical specs, compatibility details, and installation notes to assist professionals and DIY builders alike.

Compatible Engines and Applications

The crankshaft and related components in this section are compatible with:

  • Cummins 4B 3.9L – Naturally aspirated industrial and generator engines

  • Cummins 4BT 3.9L – Turbocharged variants for marine and equipment applications

  • Cummins 4BTA 3.9L – Advanced emissions or marine-certified versions

They are commonly used in:

  • Marine propulsion and gensets

  • Commercial generators and stationary pumps

  • Forklifts, agricultural machinery, and construction equipment

Shop Cummins 4B Crankshaft Components Now

Explore our in-stock selection of crankshaft parts for Cummins 4B, 4BT, and 4BTA engines. Whether you're completing a full overhaul or addressing an isolated crankshaft failure, Diesel Pro Power delivers quality, support, and fast shipping—backed by decades of experience in the diesel engine industry.

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