Transmission Removal and Reinstallation Procedures For Allison M & MH Marine Transmissions

April 8, 2025

Disconnecting Cooling and Control Systems


Step-by-Step Cooling System Disconnection


Drain Oil Cooler and Hoses


Disconnect Temperature and Pressure Sensors


Remove Control Linkages and Shift Cables


Remove Breather and Fill Tube Cap


Supporting the Weight Safely


Required Tools and Equipment


Lifting Techniques and Safety Tips


Removing Fasteners and Couplings


Engine to Transmission Fasteners


Shaft Coupling and Propeller Shaft Detachment


Block the Propeller Shaft


Remove Output Flange Bolts


Check for Wear


Extracting from Engine Room


Planning the Extraction Route


Reinstallation Alignment Tips


Preparation Before Reinstallation


Aligning Input Shaft and Bell Housing


Coupling the Output Shaft


Final Pre-Start Checklist


Summary


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Transmission Removal and Reinstallation Procedures For Allison M & MH Marine Transmissions

Hydraulic Control System Overview and Testing For Allison M & MH Marine Transmissions

April 8, 2025

Overview of the Hydraulic Control System


Valve Body Components and Layout


Selector Valve Assembly:


Internal Passages:


Pressure Regulation Port:


Auxiliary Check Valves and Dump Valves:


Pressure Testing Procedures


Required Tools:


Test Setup:


Interpreting Results:


Solenoid Function and Replacement


Function of Solenoids:


Symptoms of Faulty Solenoids:


Replacement Procedure:


Internal Passage Cleaning


When to Clean Passages:


Cleaning Steps:


Important Tips:


Testing With Hydraulic Gauges


Recommended Gauges:


What to Monitor:


Testing Intervals:


Data Logging:


System Upgrades and Preventative Improvements


Available Enhancements:


Best Practices:


Common Hydraulic Failures and Troubleshooting


Issue: Delayed engagement in forward or reverse


Issue: Overheating


Issue: Fluctuating oil pressure


Issue: No clutch engagement


Issue: Oil leaks


Conclusion


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Hydraulic Control System Overview and Testing For Allison M & MH Marine Transmissions

Oil Pump Service For Allison M & MH Marine Transmissions

April 8, 2025

 


Identifying Symptoms of Oil Pump Failure


Common Symptoms of Oil Pump Issues:


Accessing and Removing the Oil Pump


Step-by-Step Removal:


Rotor and Housing Wear Inspection


Key Inspection Points:


Visual Inspection Tips:


Replacing or Rebuilding Components


Rebuild Steps:


Replace with New Pump:


Reinstallation and Priming


Reinstallation Procedure:


Priming the Oil System:


Final Notes on Oil Pump Service


Parts Available From Diesel Pro Power


Benefits:


FAQ


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Oil Pump Service For Allison M & MH Marine Transmissions