Types of 4D56 Crankshafts
The Mitsubishi 4D56 diesel engine is a popular power unit found in many vehicles, particularly in older Mitsubishi L200 pickup trucks and various Asian and Western car brands. This four-cylinder, in-line configuration engine relies on a robust crankshaft to convert reciprocating piston motion into rotational power that drives the vehicle.
Engineering Note: The 4D56T crankshaft is a specialized turbocharged variant designed to handle the increased power and torque output of turbocharged engines. These crankshafts feature reinforced journals and improved metallurgy to withstand higher stress levels.
Cast Iron Crankshaft
The most common type for 4D56 engines, cast iron crankshafts offer excellent durability and cost-effectiveness.
Key Features:
- Four main journals with precision machining
- Four connecting rod journals
- Individual crankpin for each cylinder
- Excellent heat dissipation properties
- Cost-effective manufacturing process
Best for: Standard engine rebuilds and everyday applications
Forged Steel Crankshaft
Premium option for high-performance and heavy-duty applications requiring superior strength and durability.
Key Features:
- Higher tensile strength than cast iron
- Better resistance to fatigue and stress
- Enhanced ability to handle higher RPMs
- Superior durability under extreme conditions
- Available as aftermarket performance upgrades
Best for: Racing, heavy towing, and high-performance applications
| Feature | Cast Iron Crankshaft | Forged Steel Crankshaft |
|---|---|---|
| Durability | Good | Excellent |
| Cost | Lower | Higher |
| Weight | Heavier | Lighter |
| Heat Resistance | Good | Excellent |
| Torque Handling | Standard | Enhanced |
| Availability | Widely Available | More Limited |
Specifications and Maintenance of 4D56 Crankshafts
Key Specifications
| Specification | Standard Range | Notes |
|---|---|---|
| Cylinder Configuration | 4-6 cylinders | Most common is 4-cylinder inline |
| Rotation Direction | Clockwise (viewed from front) | Standard for most automotive applications |
| Stroke Length | 86-95 mm | Affects torque characteristics |
| Bore Diameter | 85-90 mm | Works with corresponding pistons |
| Main Journal Diameter | 52-58 mm | Critical for proper bearing fit |
| Rod Journal Diameter | 45-50 mm | Must match connecting rod specifications |
Essential Maintenance Practices
Proper maintenance significantly extends the service life of 4D56 crankshafts and prevents costly repairs. Implementing these key practices will help ensure optimal performance:
Regular Oil Changes
Clean oil provides crucial lubrication that prevents metal-to-metal contact between the crankshaft and bearings.
Best Practice: Change oil every 3,000 miles or 3 months, whichever comes first. Use manufacturer-recommended oil grade.
Load Management
Preventing excessive strain on the engine helps preserve crankshaft integrity.
Best Practice: Follow manufacturer's loading recommendations and avoid prolonged operation on steep inclines when possible.
Expert Advice: When the engine warning light illuminates, address the issue promptly. Many engine problems start small but can quickly escalate to damage the crankshaft if left unattended. Regular engine diagnostics can catch potential issues before they affect the crankshaft.
| Maintenance Task | Frequency | Benefit to Crankshaft |
|---|---|---|
| Engine Oil Change | Every 3,000 miles or 3 months | Prevents scoring and excessive wear of journals |
| Engine Tune-up | Every 15,000-30,000 miles | Ensures balanced operation and reduces vibration stress |
| Bearing Inspection | During major service intervals | Prevents catastrophic failure from bearing wear |
| Belt and Pulley Check | Every 30,000 miles | Prevents uneven loads on crankshaft front journal |
| Monitor Engine Warning Lights | Continuous | Early detection of potential problems |
How to Choose the Right 4D56 Crankshaft
Selecting the appropriate 4D56 crankshaft requires careful consideration of several factors to ensure compatibility, performance, and longevity. Follow these guidelines to make an informed decision:
Application Assessment
Match the crankshaft specifications to your vehicle's specific requirements and usage patterns.
- Heavy-duty trucks need high-torque crankshafts
- Lightweight vehicles work well with standard specs
- Performance applications may require forged models
Material Considerations
The crankshaft material significantly impacts performance and lifespan.
- Cast iron: Standard, cost-effective option
- Forged steel: Premium choice for performance
- Billet steel: Ultimate strength for racing (specialty)
Important Warning: Never attempt to use a 4D56 crankshaft in non-compatible engines without professional modification. Improper fitment can lead to catastrophic engine failure, personal injury, and costly repairs.
| Selection Factor | Considerations | Impact on Performance |
|---|---|---|
| Engine Specifications | Match to original specs or planned upgrades | Ensures proper fit and function |
| Vehicle Usage | Daily driver vs. heavy duty vs. performance | Determines durability requirements |
| Budget Constraints | Balance cost with quality needs | Affects long-term value and performance |
| Manufacturer Reputation | Research brand reliability and support | Influences part longevity and warranty options |
| Balancing Specifications | Consider internal/external balance requirements | Critical for smooth operation and vibration reduction |
| Journal Dimensions | Verify compatibility with bearings and rods | Essential for proper assembly and oil clearance |
Pro Selection Tip: When possible, choose a crankshaft with a nitride treatment or similar surface hardening process. These treatments significantly increase wear resistance and can extend the crankshaft's service life by 30-50% under normal operating conditions.
DIY 4D56 Crankshaft Replacement Guide
Replacing a 4D56 crankshaft is a complex but manageable procedure with the right tools, preparation, and attention to detail. Follow this comprehensive step-by-step guide to successfully complete this major engine repair.
Safety Warning: Crankshaft replacement is an advanced mechanical procedure. If you're unsure about any step, consult a professional mechanic. Always wear appropriate safety gear including eye protection and gloves.
Tools and Materials Needed:
| Tool/Material | Purpose |
|---|---|
| Socket set and wrenches | Removing fasteners and components |
| Engine hoist | Removing engine (if necessary) |
| Torque wrench | Proper tightening of critical fasteners |
| Bearing scraper | Cleaning bearing surfaces |
| Plastigage | Measuring bearing clearances |
| Engine assembly lubricant | Lubricating bearing surfaces during assembly |
| New bearing sets | Replacing worn bearings |
| Engine gasket set | Replacing necessary gaskets |
Replacement Procedure:
-
Secure the Vehicle
Park on a flat surface, engage the parking brake, and place wheel chocks on the wheels opposite to your work area. This prevents accidental movement during the procedure.
-
Disconnect the Battery
Remove the negative terminal first, then the positive to eliminate electrical hazards. Remove any components blocking access to the engine, such as air intake, exhaust components, and radiator as needed.
-
Drain Engine Fluids
Properly drain and dispose of engine oil and coolant according to local regulations. This prevents spillage during component removal.
-
Remove the Crankshaft Pulley
Use a pulley removal tool to safely extract the pulley from the front of the crankshaft without damaging components.
-
Remove Main Bearing Caps
Carefully loosen and remove the bolts securing the main bearing caps in the reverse order of the tightening sequence. Mark each cap's position to ensure proper reinstallation.
-
Extract the Old Crankshaft
Lift the crankshaft straight up and out of the engine block, being careful not to damage the main bearing journals or cylinder walls.
-
Inspect and Clean
Thoroughly examine the engine block bearing surfaces, oil passages, and related components. Clean all surfaces that will contact the new crankshaft.
-
Install New Bearings
Place new main bearings in the engine block and bearing caps, ensuring proper alignment with oil holes and applying engine assembly lubricant.
-
Install the New Crankshaft
Carefully lower the new crankshaft into position, aligning it with the main bearing journals. Ensure it rotates freely after initial placement.
-
Reinstall Main Bearing Caps
Place the caps in their original positions and torque the bolts to manufacturer specifications in the proper sequence, typically using a three-stage tightening process.
-
Verify Crankshaft Movement
Check that the crankshaft rotates smoothly by hand before proceeding with further assembly.
-
Complete Reassembly
Reinstall all removed components in reverse order, including the crankshaft pulley, timing components, oil pan, and external accessories.
-
Refill Fluids and Test
Add fresh oil and coolant, then start the engine to check for proper operation, unusual noises, or leaks.
Expert Assembly Tip: When installing the main bearing caps, apply a small amount of thread-locking compound to the bolts and follow a strict three-stage torque sequence: 1) 30% of final torque, 2) 70% of final torque, and 3) 100% of final torque. This ensures even clamping force and prevents warping.
Frequently Asked Questions
A 4D56 crankshaft is a critical component of the Mitsubishi 4D56 diesel engine, commonly found in various Mitsubishi vehicles and other Asian and Western car brands. This precision-engineered part converts the reciprocating (up-and-down) motion of the pistons into rotational motion that powers the vehicle's drivetrain. It features multiple journals that rotate within bearings and offset throws that connect to the pistons via connecting rods. The crankshaft design is specific to the 4D56 engine's displacement, firing order, and power requirements.
When purchasing a 4D56 crankshaft, buyers typically consider these key factors:
- Material quality - Cast iron for standard applications, forged steel for high-performance needs
- Dimensional accuracy - Proper journal diameters and stroke length to match engine specifications
- Surface finish - Smooth journal surfaces for optimal bearing life
- Balance specifications - Properly balanced to reduce vibration
- Manufacturer reputation - Reliable brands with quality control standards
- Warranty coverage - Protection against manufacturing defects
- Price vs. quality balance - Value proposition considering the intended application
Professional engine builders also pay attention to oil passage design, hardening treatments, and compatibility with existing engine components.
The 4D56 crankshaft is specifically designed for the Mitsubishi 4D56 engine family and is not directly compatible with other engine types without significant modifications. Major compatibility issues include:
- Journal diameters and spacing specific to 4D56 block dimensions
- Counterweight design matched to 4D56 firing order and balance requirements
- Oil passage layout designed for the 4D56 lubrication system
- Stroke length optimized for 4D56 displacement and rod ratios
While professional engine builders may modify a 4D56 crankshaft for use in custom applications, such modifications typically require extensive machining, balancing, and engineering considerations. These modifications often compromise durability and are generally not recommended for regular use. For optimal performance and reliability, it's best to use engine-specific crankshafts as designed by manufacturers.
The 4D56 crankshaft has earned a reputation for good reliability when properly maintained and used within its design parameters. Factory 4D56 crankshafts are engineered to handle the standard power output and operating conditions of these diesel engines, typically providing many years of service.
Key factors affecting 4D56 crankshaft reliability include:
- Regular oil changes - Critical for proper lubrication and bearing life
- Operating conditions - Extreme loads or RPMs can reduce lifespan
- Manufacturer quality - OEM and quality aftermarket parts typically outperform budget options
- Engine tuning - Modified engines with increased power may stress standard crankshafts
- Installation quality - Proper bearing clearances and torque specifications are essential
For high-performance applications or engines producing significantly more power than stock, upgrading to a forged steel crankshaft is recommended for improved reliability under increased stress.