April 7, 2025
Overview of Rebuild Kits Available For Twin Disc MG521
1. Basic Service Kit
2. Standard Rebuild Kit
3. Master Overhaul Kit
Comparison to OEM Parts
OEM Pros:
OEM Cons:
Diesel Pro Aftermarket Pros:
Aftermarket Misconceptions:
Diesel Pro Power Aftermarket Kits With OEM Matching Warranty
What the Warranty Covers:
Support You Can Trust
Contents of Standard Rebuild Kits For MG521
1. Clutch Plate Kit
2. Bearing Set
3. Gasket & Seal Set
4. Snap Rings and Washers
5. Oil Filter
6. Hardware (in Master Kits)
Plate Kits, Gasket Kits, Seal Kits, and Bearings
Clutch Plate Kits
Gasket Kits
Seal Kits
Bearing Kits
When to Replace Full Assemblies vs. Individual Parts
Replace Individual Parts If:
Replace Full Assemblies If:
Lead Times, Support, and Ordering From Diesel Pro
1. Lead Times
2. Shipping Options
3. How to Order
Conclusion: Rebuilding With Confidence and Clarity
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April 7, 2025
Common Wear Components (Clutch Plates, Seals, Bearings)
1. Clutch Plates
2. Bearings
3. Oil Seals and Gaskets
Recommended Replacement Intervals
Component
Recommended Interval
Notes
Interchangeable Parts and Aftermarket Options
Interchangeable Components
Diesel Pro Power Premium Rebuild Kits
What’s Included in a Premium Kit:
Why Choose Diesel Pro Power Kits:
Importance of Using Proper Gasket and Seal Kits
Why Gasket Quality Matters:
What to Look for in a Gasket/Seal Kit:
Seal Installation Tips:
Torque Specs for Major Component Reinstallation
Torque Specification Chart for MG521
Component
Torque Value (lb-ft)
Torque Tips:
Final Tips for Reassembly and Post-Replacement Testing
1. Lubricate All Bearings and Seals
2. Rotate Input Shaft By Hand
3. Fill With Correct Oil
4. Prime the Hydraulic System
5. Run Through Full Shift Cycle
6. Inspect for Leaks
Conclusion: Confidence Through Correct Parts and Rebuild Practices
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April 7, 2025
Disconnecting From Engine and Shaft
1. Prepare the Work Area
2. Drain Hydraulic and Control Lines
3. Detach the Propeller Shaft Flange
4. Disconnect From the Engine Bell Housing
Draining Oil and Safe Containment
1. Tools and Materials Needed
2. Draining Process
3. Safe Oil Disposal
4. Cleaning Up
Lifting Techniques and Rigging Requirements
1. Rigging Tools Required
2. Rigging Procedure
3. Storage
Inspection Before Reinstallation
1. Inspect the Engine Bell Housing
2. Examine the Mounting Base
3. Review Shaft and Coupling Condition
4. Inspect Hardware and Fasteners
5. Pre-Install Clutch Function Test
Re-Torquing Mounting and Coupling Hardware
1. Mounting Bolt Torque Specs
Bolt Size
Torque (lb-ft)
2. Flange Coupling Torque Specs
3. Control Linkage Torque
Oil Refill and Priming Procedure
1. Oil Type and Capacity
2. Filling Procedure
3. Priming the System
Operational Checks After Reinstallation
1. First Start-Up
2. Shift Engagement
3. Visual Inspection
4. Vibration and Alignment Check
5. Final Checks Under Load
6. Documentation and Logging
Conclusion: Seamless Removal and Reinstallation for MG521 Reliability
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April 7, 2025
Mechanical Control Linkage vs. EC300 Electronic Controls
Mechanical Control Linkage
EC300 Electronic Controls
Cable Routing and Securement
Choosing the Right Cables
Routing Guidelines
Bulkhead and Deck Penetrations
Post-Installation Check
Calibrating Control Responses
Mechanical Cable Calibration
EC300 Calibration
Synchronization With Throttle Systems
Mechanical Systems
EC300 Synchronization
Troubleshooting Control Signal Loss
Mechanical System Failure
Electronic System Failure
Control System Bleed Procedures (If Applicable)
When Bleeding Is Needed
Tools Needed
Bleeding Procedure
Final Integration Checklist
Conclusion: Precision Control for Long-Term Reliability
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April 7, 2025
Slipping or Delayed Engagement
Symptoms:
Potential Causes:
Solutions:
Unusual Noises (Whine, Grind, Knock)
Symptoms:
Potential Causes:
Solutions:
High Operating Temperatures
Symptoms:
Potential Causes:
Solutions:
Oil Leaks (Input/Output Seal, Sump)
Symptoms:
Potential Causes:
Solutions:
Low Oil Pressure
Symptoms:
Potential Causes:
Solutions:
Excessive Vibration
Symptoms:
Potential Causes:
Solutions:
Troubleshooting Charts and Flow Processes
1. Engagement Issues
2. Overheating
3. Noisy Operation
4. Oil Leak
5. Vibration
Emergency Bypass Procedures
1. Manual Engagement
2. Overriding EC300 Controls
3. Cooling System Bypass
4. Limp Mode
Conclusion: Confidence Through Diagnostic Clarity
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April 7, 2025
Recognizing Signs of Wear or Damage in the MG521
1. Abnormal Noise
2. Excessive Heat
3. Metal Shavings or Debris in Oil
Disassembly Procedure for the MG521
1. Tools and Equipment Required
2. Safety Preparation
3. Disassembly Steps
Gear Tooth Inspection – Pitting, Wear, Scoring
1. Visual Inspection Checklist
2. Acceptable Wear Limits
Measuring Bearing Play and End Float
1. Radial Play Check
2. End Float (Axial Play)
3. Bearing Surface Inspection
Cleaning Procedures for Removed Components
1. Cleaning Process
2. Special Considerations
Installing New Gears and Bearings in the MG521
1. Bearing Installation
2. Gear Installation
3. Lubrication Before Startup
Rechecking Gear Backlash and Alignment
1. Measuring Backlash
2. Adjusting Backlash
3. Gear Tooth Contact Pattern
Reassembly and Torque Specs for the MG521
1. Gasket and Seal Replacement
2. Fastener Torque Table
Component
Torque (lb-ft)
3. Final Reassembly Steps
Post-Repair Testing and Diagnostics
1. Dry Run and Leak Check
2. Engagement Testing
3. Vibration and Noise Monitoring
4. Sea Trial (Optional)
Conclusion: Long-Term Reliability Through Precision Repair
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