Introduction For Allison M & MH Marine Transmissions

• Overview of Allison M & MH series in marine applications 
• Legacy, reliability, and usage in commercial/recreational vessels 
• Why proper servicing matters: performance, longevity, and safety
  

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General Specifications For Allison M & MH Marine Transmissions

• Physical dimensions 
• Weight 
• Input/output shaft specs 
• Rotation direction and gear ratios 
• Torque handling and horsepower limits
  

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Installation Guidelines For Allison M & MH Marine Transmissions

• Pre-installation checklist 
• Mounting procedures 
• Alignment with engine and shaft 
• Fastener torque specifications 
• Sealing surfaces and gasket prep
  

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Initial Startup Procedure For Allison M & MH Marine Transmissions

• Priming lubrication systems 
• Fluid type and fill instructions 
• Manual engagement and rotation 
• Air testing and pressure checks 
• First-run operating parameters 
  

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Scheduled Maintenance For Allison M & MH Marine Transmissions

• Daily, weekly, and seasonal checks 
• Oil and filter change intervals 
• Temperature and pressure monitoring 
• Linkage and cable adjustment 
• Fluid sampling for wear indicators
  

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Inspecting and Replacing Bearings and Gears For Allison M & MH Marine Transmissions

• Identifying signs of wear 
• Disassembly prep and safety 
• Gear inspection tolerances 
• Bearing removal and press-fit install 
• Rechecking alignment and backlash
  

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Clutch Inspection and Replacement Procedures

• Accessing clutch pack 
• Wear patterns and friction plate scoring 
• Spring, disc, and piston checks 
• Clearance measurements 
• Reassembly with proper preload
  

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Oil Pump Service For Allison M & MH Marine Transmissions

• Identifying symptoms of failure 
• Accessing and removing oil pump 
• Rotor and housing wear inspection 
• Replacing or rebuilding components 
• Reinstallation and priming
  

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Hydraulic Control System Overview and Testing

• Valve body components and layout 
• Pressure testing procedures 
• Solenoid function and replacement 
• Internal passage cleaning 
• Testing with hydraulic gauges
  

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Shift Lever and Cable Adjustment Procedures

• Inspecting and adjusting shift linkage 
• Free-play and detent engagement 
• Correct neutral and gear alignment 
• Replacing worn bushings or cables 
• Verifying cockpit-to-transmission shift timing
  

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Troubleshooting Common Problems For Allison M & MH Marine Transmissions

• Slipping in gear 
• No engagement in forward or reverse 
• Overheating 
• Noise under load 
• Oil contamination or leakage
  

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Transmission Removal and Reinstallation Procedures

• Disconnecting cooling and control systems 
• Supporting the weight safely 
• Removing fasteners and couplings 
• Extracting from engine room 
• Reinstallation alignment tips
  

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Parts and Component Replacement Guide For Allison M & MH Marine Transmissions

• Gasket and seal kits 
• Bearing and gear sets 
• Clutch discs and pressure plates 
• Oil pumps and shafts 
• Housing and input/output assemblies
  

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Rebuild Kit and Aftermarket Parts Overview For Allison M & MH Marine Transmissions

• Benefits of aftermarket kits from Diesel Pro Power 
• What’s included in a typical rebuild kit 
• Matching components to serial numbers 
• Ordering complete replacement units vs. individual components 
• Warranty and quality assurance 
  

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50 FAQs – Frequently Asked Questions For Allison M & MH Marine Transmissions

Disclaimer

For precise tolerances, torque specs, and advanced diagnostics, always refer to the OEM service manual when available. This guide is a practical reference based on standard service practices.

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