50 Frequently Asked Questions (FAQs) for Twin Disc MG5075A Marine Transmission

March 19, 2025

Parts Catalog for Twin Disc MG5075A Marine Transmissions
Plate Kit For Twin Disc MG5075A Marine Transmission
Gasket Kits For Twin Disc MG5075A Marine Transmission

Introduction

The Twin Disc MG5075A marine transmission is a high-performance and durable gearbox designed for marine applications requiring smooth operation, efficient power transfer, and reliable shifting. Vessel operators, mechanics, and marine engineers frequently have questions about installation, operation, troubleshooting, maintenance, and compatibility.

This comprehensive 50-question FAQ guide addresses the most common inquiries about the Twin Disc MG5075A, providing detailed answers to ensure optimal performance and long-term reliability.

1. General Information About Twin Disc MG5075A

1. What is the Twin Disc MG5075A transmission used for?

The Twin Disc MG5075A is a marine transmission designed for boats, yachts, fishing vessels, and workboats, providing smooth gear shifting and efficient power transfer.

2. What type of engines is the MG5075A compatible with?

This transmission is compatible with various marine diesel engines, particularly those in the 200-400 HP range, but always verify with the engine manufacturer for proper compatibility.

3. What are the key specifications of the Twin Disc MG5075A?

✔ Type: Marine Gearbox
✔ Clutch: Hydraulically actuated
✔ Reduction Ratios: Multiple configurations available
✔ Mounting: Direct engine coupling
✔ Cooling: External oil cooler required

4. How much does the Twin Disc MG5075A transmission weigh?

The approximate weight is 260 to 300 lbs (118-136 kg), depending on the configuration.

5. What is the maximum input RPM for this transmission?

The maximum input RPM varies based on the engine and application, but it is typically between 2,500 and 3,000 RPM.

2. Installation and Setup FAQs

6. What should be checked before installing the Twin Disc MG5075A?

✔ Ensure the engine flywheel housing matches the transmission.
✔ Verify mounting hardware and alignment.
✔ Check fluid levels before startup.

7. How do I properly align the MG5075A transmission during installation?

Use a dial indicator to ensure the input and output shafts are aligned within 0.002 to 0.005 inches.

8. Can the MG5075A be mounted in different orientations?

It is typically mounted horizontally, but some applications allow for slightly angled installations—always refer to the Twin Disc manual.

9. Does this transmission require an external oil cooler?

Yes, an external oil cooler is required to maintain proper operating temperatures and prevent overheating.

10. What are the recommended torque settings for mounting bolts?

✔ Transmission mounting bolts: 75-90 ft-lbs
✔ Clutch pack fasteners: 40-55 ft-lbs
✔ Output shaft coupling bolts: 80-100 ft-lbs

3. Maintenance and Lubrication FAQs

11. How often should the transmission fluid be changed?

Every 250 hours of operation or annually, whichever comes first.

12. What type of oil should I use in the Twin Disc MG5075A?

✔ SAE 30 or SAE 40 non-detergent oil (marine-grade)
✔ Synthetic options for high-performance applications

13. How much fluid does the MG5075A hold?

The oil capacity varies, but typically requires 2.5 to 3.5 quarts (2.4 to 3.3 liters).

14. How do I check the transmission fluid level?

✔ Run the engine at idle for 5 minutes.
✔ Shift into neutral and turn off the engine.
✔ Use the dipstick to check oil level.

15. What are the signs of contaminated transmission fluid?

✔ Dark or burnt-smelling oil
✔ Foamy or milky appearance (water contamination)
✔ Metallic particles in the oil

4. Troubleshooting and Repair FAQs

16. Why is my MG5075A transmission slipping?

✔ Low hydraulic pressure
✔ Worn clutch plates
✔ Contaminated transmission fluid

17. What causes hard shifting in the Twin Disc MG5075A?

✔ Overfilled fluid reservoir
✔ Improper shift linkage adjustment
✔ Hydraulic system issues

18. How do I diagnose an overheating transmission?

✔ Check fluid levels and cooling system.
✔ Inspect oil cooler for blockages.
✔ Ensure correct transmission load balancing.

19. Why is my transmission making a grinding noise?

✔ Worn-out gears or bearings
✔ Improper fluid levels
✔ Misalignment of shafts

20. What should I do if my transmission won’t shift into gear?

✔ Check hydraulic pressure levels.
✔ Inspect shift cables or electronic controls.
✔ Ensure clutch engagement is functioning properly.

5. Storage and Long-Term Use FAQs

21. How should I store a Twin Disc MG5075A transmission?

✔ Drain old fluid and refill with storage oil.
✔ Keep in a temperature-controlled environment.
✔ Rotate input/output shafts every 3 months.

22. How do I restart the transmission after long-term storage?

✔ Drain storage oil and refill with fresh transmission fluid.
✔ Manually rotate shafts to check for free movement.
✔ Perform a bench test before reinstalling.

23. What precautions should I take to prevent corrosion during storage?

✔ Apply anti-rust protective coatings.
✔ Use desiccant packs or moisture absorbers.

24. Do I need to flush the hydraulic system before reinstalling?

Yes, flushing removes old fluid, debris, and contaminants.

25. Can I store the MG5075A transmission outdoors?

✔ Not recommended, but if necessary, cover with waterproof breathable material.

6. Performance and Optimization FAQs

26. How do I improve transmission efficiency?

✔ Use high-quality transmission fluid.
✔ Perform regular maintenance.
✔ Ensure proper shaft alignment.

27. Can I use synthetic oil in my MG5075A transmission?

✔ Yes, high-grade synthetic transmission fluid can be used.

28. How do I reduce transmission noise?

✔ Ensure correct fluid levels.
✔ Inspect bearings and gears for wear.

29. What is the recommended operating temperature?

✔ Ideally, 160°F to 190°F (71°C to 88°C).

30. Can I increase the transmission’s torque capacity?

✔ Not without replacing internal components or using reinforced clutch plates.

7. Performance and Optimization FAQs

31. What is the recommended operating temperature for the MG5075A?

✔ The ideal operating temperature is between 160°F and 190°F (71°C to 88°C).
✔ Excessive heat (above 200°F/93°C) can damage components and reduce fluid efficiency.

32. What happens if the transmission overheats?

✔ Fluid breakdown reduces lubrication, increasing wear.
✔ Clutch packs may slip or fail due to thermal expansion.
✔ Overheating can cause seals to harden and leak.

👉 Solution: Inspect and clean the cooling system, fluid levels, and filters regularly.

33. Can I increase the transmission’s torque capacity?

✔ Not without internal modifications—the MG5075A is designed for a specific torque rating.
✔ Upgrading to reinforced clutch plates may help in some cases.
✔ For higher torque needs, consider a larger Twin Disc transmission model.

34. How can I improve fuel efficiency with the MG5075A?

✔ Ensure transmission is properly aligned with the engine.
✔ Maintain clean hydraulic fluid and correct oil levels.
✔ Use a propeller matched to the engine-transmission ratio for optimal performance.

35. How do I know if my transmission is not performing efficiently?

✔ Delayed gear engagement.
✔ Higher-than-normal fuel consumption.
✔ Unusual noises or excessive vibration.
✔ Overheating under normal conditions.

👉 Solution: Check for misalignment, low hydraulic pressure, fluid degradation, or component wear.

36. Can I modify the MG5075A for high-performance applications?

✔ Some upgrades are possible, including synthetic oil use, precision alignment, and cooling system enhancements.
✔ Modifying internal components is not recommended as it may void the warranty.

37. How does gear ratio affect performance in marine transmissions?

✔ A higher gear ratio increases torque output but reduces propeller RPM.
✔ A lower gear ratio allows faster shaft speeds, improving top-end speed.
✔ Choosing the correct gear ratio for your vessel type is crucial for efficiency.

38. Can a faulty transmission cause increased engine load?

✔ Yes, if the transmission has high friction, misalignment, or slipping clutches, the engine must work harder, increasing fuel use.
✔ A properly calibrated and maintained transmission ensures optimal load balancing.

39. What should I do if my transmission hesitates before shifting?

✔ Check hydraulic pressure and ensure fluid levels are correct.
✔ Inspect shift linkages for misalignment or excessive play.
✔ Replace clogged filters that may be restricting fluid flow.

40. How do I know if my hydraulic pump is failing?

✔ Symptoms of a failing hydraulic pump include:

Sluggish gear shifting.
Whining or humming noises.
Fluctuating hydraulic pressure readings.
Overheating transmission fluid.

👉 Solution: Inspect for leaks, worn-out seals, or pump inefficiencies, and replace if necessary.

8. Long-Term Use and Storage FAQs

41. Can I store my transmission long-term without fluid?

✔ Not recommended—internal components can corrode.
✔ If long-term storage is needed, fill with storage oil containing corrosion inhibitors.

42. How do I protect my stored transmission from corrosion?

✔ Apply a light coating of oil to all internal components.
✔ Store in a temperature-controlled, moisture-free environment.
✔ Use desiccant packs to absorb humidity.

43. How often should I rotate the transmission shafts during storage?

✔ Rotate input and output shafts every 3 months to prevent seal hardening and component sticking.

44. What happens if transmission seals dry out during storage?

✔ Dried-out seals can crack and leak once the transmission is restarted.
✔ Solution: Apply seal conditioner before storage and inspect seals before reinstallation.

45. Should I start the engine periodically if my vessel is in storage?

✔ Yes, running the engine for 15-20 minutes every month helps keep fluid circulating and prevents seal damage.

46. What should I inspect before restarting a stored transmission?

✔ Check oil levels and condition.
✔ Inspect seals and gaskets for leaks.
✔ Manually rotate the input/output shafts before startup.

47. Do I need to replace transmission fluid after storage?

✔ If stored for less than 6 months, check condition and top off.
✔ If stored for over a year, drain and replace with fresh fluid.

48. What are the risks of improper storage?

✔ Corrosion and rust.
✔ Seals drying out and failing.
✔ Fluid contamination leading to poor performance.

👉 Solution: Follow proper storage guidelines to maintain transmission integrity.

49. How do I know if a stored transmission is still in good condition?

✔ Perform a bench test before reinstallation.
✔ Check for unusual noises, vibrations, and leaks.
✔ Ensure fluid is clean and free from debris.

50. What is the best way to restart a transmission after years in storage?

✔ Drain old oil and flush the system before adding fresh fluid.
✔ Manually engage and disengage the clutch to ensure smooth operation.
✔ Perform a full operational test before placing under load.

Conclusion

The Twin Disc MG5075A marine transmission is a high-performance, durable system that requires proper maintenance, troubleshooting, and care to maximize its efficiency and lifespan.

Key Takeaways:

✔ Use the correct fluids and change them at proper intervals.
✔ Check for signs of wear and misalignment to prevent breakdowns.
✔ Adjust and calibrate hydraulic pressure and shift linkages for smooth performance.
✔ Follow long-term storage procedures to prevent corrosion and fluid degradation.

By following these 50 comprehensive FAQs, vessel operators, mechanics, and marine engineers can prevent costly failures, improve performance, and ensure the longevity of the Twin Disc MG5075A transmission.