MODEL MG 5050 MARINE TRANSMISSION Caterpillar

When the words "use again" are in the description, the specification given can be used to determine if a part can be used again If the part is equal to or within the specification given, use the part again

When the word "permissible" is in the description, the specification given is the maximum or minimum" tolerance permitted before adjustment, repair and/or new parts are needed.

A comparison can be made between the measurements of a worn part and the specifications of a new part to find the amount of wear. A part that is worn can be safe to use if an estimate of the remainder of its service life is good. If a short service life is expected, replace the part.

This section of the maintenance manual has been prepared to assist maintenance personnel in troubleshooting equipment. When troubleshooting the equipment, consider the entire power package.

In the format that follows, a sympton or problem wiil be stated. A possible cause and remedy will follow to help determine the transmission malfunction.

Problem 1: Low Main Oil Pressure

Probable Cause:

1. Partially clogged oil strainer.

Remove and clean oil strainer.

2. Stuck pressure regulation piston in selector valve assembly.

Remove control valve assembly. Disassemble the valve and clean the piston. Check the valve spring.

3. Broken piston rings on clutch shafts.

Remove the manifold and inspect piston rings. Replace broken piston rings.

4. Damaged or worn oil pump assembly.

Replace damaged or worn oil pump assembly.

5. Incorrect linkage adjustment to control valve assembly.

Adjust linkage so that control valve stem is indexed properly by detent.

6. Clogged or plugged orifice plate of control valve assembly.

Remove orifice plate cover and clean the parts.

7. Shims required between inner and outer springs and rate-of-rise piston.

Shim as required.

8. Badly worn grooves on clutch shaft.

Replace shaft and piston rings.

9. Broken or badly worn seal rings on clutch piston.

Replace seal rings.

Problem 2: No Oil Pressure Or Erratic Low Pressure At Control Valve

Probable Cause:

1. Oil pump suction strainer plugged.

Remove and clean strainer.

2. Oil level low.

Check oil level and correct.

3. Air leak on suction side of pump.

Correct cause of air leak.

4. Pump drive on reverse clutch shaft broken.

Disassemble and repair as required.

5. Control valve regulating valve stuck in open position.

Remove, disassemble, clean and repair the control valve.

6. Oil pump defective.

Replace the oil pump.

Problem 3: High Main Oil Pressure:

Probable Cause:

1. Regulating valve stuck.

Remove and clean regulating valve.

2. Faulty spring.

Check and possibly replace spring.

Problem 4: High Temperature:

Probable Cause:

1. Improper oil level.

Check and fill with proper oil to the correct level.

2. Faulty heat exchanger (if used).

Inspect, repair or replace heat exchanger.

3. Clutches slipping.

Check clutch apply oil pressure. If pressure is normal, remove, disassemble and repair slipping clutch.

4. Bearing failure.

Overhaul marine transmission.

Problem 5: Excessive Noise:

Probable Cause:

1. Bearing failure.

Remove marine transmission. Disassemble and replace worn parts.

2. Worn or damaged rubber blocks.

Remove marine transmission. Replace worn or damaged rubber blocks.

Problem 6: No Neutral:

Probable Cause:

1. Clutch plates warped.

Replace clutch plates.

2. Control valve linkage incorrectly positioned.

Check and adjust control linkage.

Problem 7: Harsh Engagement:

Probable Cause:

1. Regulating piston or rate-of-rie piston stuck.

Disassemble control valve, clean and replace parts if necessary.

2. Orifice plate ball in control valve not seating properly.

Remove orifice plate cover, clean and replace parts if necessary.

Problem 8: Low Lube Oil Pressure:

Probable Cause:

1. Pump output too low.

Replace pump.

2. Pump suction strainer plugged.

Remove, clean, inspect and install the suction screen.

Problem 9: High Lube Oil Pressure:

Probable Cause:

1. Air leak on suction side of pump.

Inspect for and correct air leak.

2. Broken rear oil seal ring on clutch shaft.

Replace seal ring.

3. Partially blocked orifices and oil passages.

Clean all oil passages and orifices.