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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
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
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
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
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
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
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
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
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
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
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
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
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
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
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.
Parts for Allison Marine Transmission
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Order Allison Marine Parts Online
You may be wondering why you should consider buying all your Allison Marine transmission parts online instead of going to a physical seller. The answer is both convenience and efficiency. We now live in a society where we can buy items online and have them shipped the same day without ever leaving home.
Think of it this way — every shop you visit may not always have the part you need to get your boat back up and running. It then takes days or even weeks for the seller to track down what you’re looking for, and if you have time to wait, that’s wonderful. But if you need faster service, you probably want to find a seller who already has all the parts you need.
When you buy your Allison marine transmission parts online, you have the ability to choose from a wide selection of options that you can order with a simple click. This process will allow you to avoid having a seller over your shoulder pushing you to buy what you don’t need. Meanwhile, you can save the time and money that it takes to visit a shop and consult with the seller about the specific Marine gear part you’re looking for.
Ultimately, checking out online dealerships is the most efficient way to shop for boat parts. It will give you a level of freedom and luxury unknown to those who buy parts at brick-and-mortar shops, allowing you to browse from anywhere at any time on the day you choose. If you need to replace a part of your Allison Marine engine, why not make the process as simple and pleasant as possible?
Why Diesel Pro Power?
Why should you choose Diesel Pro Power as your online service for delivering Allison Marine transmission parts? On our website, we have every Allison Marine part for sale that you could ever need. We have two dozen categories listed on our website that you can browse through in order to find the specific part you’re looking for. And if for any reason you discover that you’re struggling to locate a part, you can reach out to us with your questions, and we’ll be happy to assist you.
Another reason Diesel Pro Power is the best place to shop for Allison Marine parts online is our intuitive, simple-to-use website. We know you want to place your order quickly and get back to your other responsibilities, so we make it our mission to keep everything as user-friendly as possible for your convenience and peace of mind.
Our customer service hours are 8 a.m. to 5 p.m. EST from Monday through Friday, but we also have forms online that you can fill out to ask any questions you may have after hours. We’re committed to helping you find and order the right part, which is why we offer special information and instructions about our Allison Marine transmission parts for sale below.
Shop Allison Marine Gear and Parts
We have all of the Allison Marine transmission parts you need to get back on the water. Being one of the most popular boat transmissions ever built, the Allison Marine M and MH models still provide boaters all around the world with dependable performance. We carry everything from the overhaul kits to the individual components, so you are sure to find what you need.
Don’t want to do the overhaul yourself? We sell entire rebuilt transmissions as part of our marine transmissions parts inventory that are ready to go. All orders ship within 24 hours, so you don’t have to wait long at all to get your boat back where it belongs.
Common Questions
What is the difference between an Allison Marine M versus Allison Marine MH transmission?
Both are built for marine use and are very similar. The main difference is that the MH transmission if built for more heavy-duty applications and are generally larger in size.
What type of oil does this transmission take?
This engine will usually use a lubricating oil of SAE 40. For cooler conditions (below 32 degrees Fahrenheit) SAE 30 may be used.
Allison Marine M General Information
- This transmission uses 6 quarts of lubricating oil.
- The maximum horsepower is between 375 and 540 horsepower, measured at the shaft.
- This model weighs about 350 pounds.
Allison Marine MH General Information
- This transmission uses between 6 to 6.5 quarts of oil. The deep profile uses the higher amount.
- This model weighs about 480 pounds.
- The maximum shaft horsepower is 230 at 1800 RPM (For MH 25, 30, 37, 45), 460 at 2100 RPM (for MH 15, 20 and 25 crew boats) and between 600 to 720 at 2300 RPM for the other models.
Bearing Maintenance and Repair
The bearings are an integral part of the Allison transmission. Here are some key points to ensure that they last with extended use.
- Bearings should be washed in mineral spirits when possible. If they are filled with hardened grease, soak them in mineral spirits.
- Look for signs that the bearings need to be replaced. These include scored, scratched or otherwise damaged rollers or balls.
- Check for any stray metal particles. If you see any in the bearings, be sure to clean them thoroughly.
- When you get new bearings, keep them in the wrapper as long as possible. If you have to place them down, do so on a piece of paper that is free of lint, instead of on a work bench.
- When installing a bearing on a shaft, heat it to 200 degrees Fahrenheit to expand for installation, by using a hotplate or an oil bath. This process should take less than 45 minutes.
Hydraulic Pump System
Of all of our Allison marine parts, one of the most popular is the hydraulic pump. This pump performs an essential function, keeping the transmission running smoothly. Here is an overview of the operation, to help with diagnosing trouble.
At the bottom of most Allison marine transmissions is the sump, where oil collects. This is then pulled up through the oil strainer, before it reaches the pump. It is then pushed through the filter, and then the cooler. The selector valve body at the top of the transmission then pushes it through to lubricate the plates, through an orifice at the top. The selector manages the flow of oil based on whether the unit is forward, reverse, or neutral. There is an orifice at the top of the transmission where the oil is dispersed into the unit. If you suspect that the oil is not circulating properly, as shown by low oil pressure, then check the oil cooler, suction line, flange and pump lines.
Here are some other details about the Allison hydraulic pump system:
- The type is positive displacement, gear pump
- Oil pressure should be 130 PSI minimum in forward gear at 1800 RPM. In reverse, fuel pressure should be at least 110 PSI at 1500 RPM.
- The oil is contained in the flywheel sump for M10 models and the oil pan for other models.
- Always check oil after the engine has been running for a few minutes, and when the transmission is around 180 to 200 degree Fahrenheit. Please note that if the power pack is at an angle, the full mark will actually be above that designated on the dipstick. Be sure to measure when it is full and mark the correct location on the dipstick.
- Low oil levels (below 6 quarts, or 6.5 quarts for deep profile models) can lead to aeration, as well as having too much oil in the sump.
- Aerated oil can have a thin, milky appearance. If the oil has been aerated, it can cause the transmission to overheat or operate irregularly.
- If the water temperature is below 50 degrees Fahrenheit (with SAE 40 oil) or below 32 degrees Fahrenheit (with SAE 30 or SAE 15W-40) then run the engine with the transmission in neutral for at least 20 minutes, or use heating equipment to reach a safe operating temperature.
- If oil pressure is low when the selector is in the forward position, check the forward piston seal rings to see if they need to be replaced. Be sure to also check the flywheel, in case there are loose or missing oil passage plugs. Check the emergency engagement bolts as well for any signs of oil leaks.
Need any Allison Marine parts not listed here? Give us a call and we can help you locate the right part, and in some cases we can special order it. If you have any questions please give us a call or click on ‘Chat’ and a member of our team will be happy to help you.
