Assembly Procedures For Twin Disc MG-540 Marine Gear

May 23, 2025

Input Group Assembly For Twin Disc MG-540 Marine Gear

Installing Input Gears and Bearings

Begin with a clean and prepped workspace. Ensure all cleaned components are lightly oiled. Stand the input group with the input end facing upward.

  1. Install Input Bearing Cups:
    • Lubricate the tapered rollers with clean oil.
    • Freeze the races if necessary and press them evenly into the housing bores.
  2. Install Test Shim Pack:
    • Place temporary shims on the housing to intentionally leave excess end play for measurement.
    • Install the driven gear using a lifting fixture or tool.
  3. Secure the Retainer:
    • Use five 1/2-13 x 1.5 capscrews torqued to 65 lb-ft.
    • Rotate the gear several times and use a dial indicator to measure end play.

End Play Measurement and Shim Selection

Use the dial indicator and lift the gear upward, then rotate 720° to measure deflection.

  • Target End Play Range: 0.0005–0.003 inches
  • Adjust shims until this range is achieved. If unsure, always err slightly toward the lower limit.
  • Once proper end play is achieved, remove the test shims and install the final shim stack.

Seal Installation and Housing Preparation

  1. Install O-Ring on Retainer Pilot and apply light oil to avoid shearing during compression.
  2. Place the Snap Ring into the driven gear groove to lock in place.
  3. Reinstall the Retainer and Cover Plate using five 1/2-13 x 1.5 capscrews torqued to 65 lb-ft1.
  4. Check Pilot and Face Runout using a dial indicator:
    • Max face runout: 0.010″
    • Max pilot runout: 0.010″

 

Output Shaft and Bearings For Twin Disc MG-540 Marine Gear

Bearing Cone and Cup Installation (Hot and Cold Techniques)

  1. Heat Bearings to 250°F if a press is not available.
  2. Place the shaft vertically with the output end up.
  3. Install the Tapered Roller Bearings:
    • Press or slide the heated bearings over the shaft and seat firmly.
    • Do not strike or hammer bearings.

End Play Adjustment and Output Seal Assembly

  1. Install the output shaft with bearings and rotate to seat components.
  2. Install a test shim pack and the seal carrier.
  3. Torque five 1/2-13 x 1.5 capscrews to 65 lb-ft.
  4. Rotate and lift gear, then read the dial indicator for end play:
    • Adjust shim pack to achieve 0.0005–0.003 inches end play.
    • Once correct, remove test pack and install final shims.

Installation of Output Gear and Clamp Plate

  1. Install the output gear onto the tapered shaft using a press or mallet and heat technique.
  2. Install the clamping plate with three 1-14 x 2 bolts.
  3. Torque bolts and install locking tabs.
  4. Bend tabs over bolt flats to lock torque.

Clutch Assemblies (Primary and Secondary) For Twin Disc MG-540 Marine Gear

Piston and Spring Installation

  1. Install the Piston Seal Ring into the shaft groove.
  2. Use a clutch compression tool (T-16240-3) to compress the spring.
  3. Install Retaining Snap Ring and verify it is seated properly.
  4. Heat clutch hubs to 250°F and install over the shaft spline.

Measuring Clutch Pack Clearance

  1. Install Friction and Steel Plates:
    • Start with a friction plate, then alternate.
    • Total: 11 friction + 12 steel + 3 additional steel plates.
  2. Measure the distance from the piston to the cylinder and from clutch plate to gear face.
  3. Calculate Released Clutch Clearance:
    • Required range: 0.165″ – 0.270″
    • Difference between forward and reverse clutch must be ≤ 0.020″
    • Add a steel plate if necessary to reduce clearance.

Friction and Steel Plate Stack-Up and Torque Specs

  1. Lower the shaft and cylinder assembly into the hub.
  2. Install four equally spaced 1/2-13 x 6 capscrews.
  3. Torque to 90 lb-ft evenly.
  4. Manually engage piston against clutch pack and torque to 20 lb-ft.
  5. Remove the clutch hub after lockup is verified.
  6. Perform runout checks at three locations:
    • Max at point A: 0.005″
    • Max at point B: 0.009″
    • Max at point C: 0.004″

Manifold and Carrier Installation For Twin Disc MG-540 Marine Gear

O-Ring Placement and Lubrication

  1. Install o-rings in all manifold recesses using clean oil.
  2. Avoid using grease that may displace under pressure or heat.
  3. Verify alignment pins and gaskets are in place on mating surfaces.

Proper Application of Loctite® Sealant

  • Apply Loctite® to:
    • Rear manifold mating surfaces
    • Threads of all 1/2-13 capscrews
  • Use a medium-strength (blue) removable threadlocker unless specified

Torque Values for Capscrews

Fastener Size

Torque (lb-ft)

Notes
1/2-13 83–97 lb-ft Main housing bolts
5/8-11 120–140 lb-ft Gear clamp fasteners
3/8-16 25–29 lb-ft Screens, retainers

All bolts must be torqued in a criss-cross pattern and threads must be lubricated with a light oil film).

Control Valve Assembly For Twin Disc MG-540 Marine Gear

GP, EC050, Mechanical, and Electric Valve Options

Mechanical Valve (XB2015A):

  • No electronics
  • Cable-actuated shifting
  • Simple and robust

Electric Valve (1020317):

  • Solenoid control
  • Works with helm switches or joysticks
  • Requires stable voltage

GP Valve With EC050 Module (1020941B):

  • Most advanced
  • Enables cruise/troll mode and diagnostics
  • Receives signals via CANbus and analog inputs

Identifying Valve Types and Installing Components

  1. Check BOM on transmission nameplate.
  2. Match control type:
    • Mechanical = Manual lever
    • EC050 = Includes GP Valve + wiring harness
    • Electric = Solenoid body only
  3. Mount valve using proper gaskets and torque values:
    • 1/2-13 socket heads: 65 lb-ft
  4. Apply Loctite to threaded ports and sensor fittings.

Basic Wiring Integration for Solenoids, Sensors, and Troll Switch

For EC050 Systems:

  • Connect solenoid leads to:
    • Terminal 10 = Troll switch input
    • Terminal 12 = Ground/reference
  • Solenoid Inputs:
    • Primary solenoid
    • Secondary solenoid
  • LED Indicators:
    • Green = Ready
    • Red = Fault
    • Flash = Diagnostic Code

Troll Switch Installation:

  • Install manual override or momentary switch at helm
  • Wire to EC050 input channel
  • Calibrate cruise vs. troll speeds after install

Sensor Integration:

  • Shaft speed pickup
  • Gear ratio calibration (Cruise mode hold for 9 seconds)
  • Oil temperature sensor (optional)

Summary Table: Key Assembly Values and Tools

Component Torque (lb-ft) Special Tool Notes
Clutch Assembly Bolts 90 T-16240-3 Compress clutch spring
Output Flange Bolts 140 Torque Wrench + Lock Plate Use Loctite + locking tab
Control Valve Screws 65 Socket Adapter Use for GP, Electric, or Mech valve
Input Seal Installation Light taps T-21552-188/191 SAE 0 / SAE 00 driver
Runout Check Tool N/A T-17473 For face/pilot measurement
Bearing Preload Tool N/A T-16240-4 For pinion torque testing

Videos About Twin Disc Transmissions

6 Reasons Your Twin Disc Transmission Has Low Oil Pressure

7 Reasons Your Twin Disc Transmission Is Overheating

3 Reasons Your Clutch Plates in Your Twin Disc Transmission Are Making Excessive Noise

 

Bull Gear On A Twin Disc Transmission 

Rebuilt Twin Disc Transmissions

 

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