13.1 50T - Gearbox Troubleshooting

Introduction

Download and fillout the Gearbox Inspection Report Checklist below before replacing any parts.

Gearbox Inspection Report Checklist

Gearbox Assembly Diagram

50-taper Gearbox

  1. Gearbox oil pump
  2. High/low gear proximity sensors or mechanical switches
  3. Spindle encoder
  4. Spindle drive belts

Gearbox Lubrication Diagrams

50T - VMC Gearbox - Orifice Vented - Lubrication

50-taper spindle:

  • Oil-pump motor [1]
  • Oil Flow Switch [2]
  • Scavenge Line [3]
  • Oil Fill Hole Plug[4]
  • Oil Filter [5]
  • Oil Pump [6]
  • Oil Level Switch [7]
  • Lubrication Tube [8]
  • Oil Nozzle [9]
  • Orifice [10]
  • Oil Reservoir [11]

50T - VMC Gearbox - Orifice Vented - Lubrication

50-taper spindle:

  • Oil-pump motor [1]
  • Oil Flow Switch [2]
  • Scavenge Line [3]
  • Oil Fill Hole Plug[4]
  • Oil Filter [5]
  • Oil Pump [6]
  • Oil Level Switch [7]
  • Lubrication Tube [8]
  • Oil Nozzle [9]
  • Orifice [10]
  • Oil Reservoir [11]

NOTE: The horizontal gearbox functions similar to the vertical mill gearbox with the pickup line in the bottom area. 

50T - Gearbox Anti-Siphon Solenoid - Lubrication

Anti-Siphon Solenoid Lubrication Components:

  • Oil-pump motor [1].
  • Gearbox [2].
  • Scavenge Line [3].
  • Oil Flow Sensor [4].
  • Filter [5].
  • Oil Pump [6].
  • Reservoir [7].
  • Lubrication Tube [8].
  • Oil Nozzle [9].
  • Anti-siphon Solenoid [10].
  • Vent Restrictor Orifice [11].
  • Oil Level Switch [12].
  • Air Vent [13]
Anti-Siphon Solenoid - Explanation 
 
  • Solenoid activates and closes the vent [13].
  • Pump pressurizes the system and allows oil to flow through.
  • When the pump stops the solenoid deactivates and the vent opens up and allows air to flow from the gearbox.
  • This allows bubbles/air into the output line [8] and breaks the natural siphon that would otherwise drain all the oil into the gearbox which will leak out of the main output shaft on to of the pulley.

Flow Switch Relocation - 50T - Gearbox - Orifice Vented

If the machine is generating alarm 2012 LOW GEARBOX OIL FLOW. Or if the machine generates LOW GEAR BOX OIL FLOW LOW GEAR BOX OIL LEVEL warnings.

Troubleshoot the gearbox.

If the gearbox continues to alarm after troubleshooting and it is configured with the flow switch at the input of the gearbox and an orifice on the oil reservoir. Perform the flow switch relocation.

Relocate the pressure switch and fittings according to the schematics.This relocation requires changing the order of the fittings and adding
PN: 58-3618. Rotate the oil filter so it is upside down.

Note: Shorten the vent hose. Adjust the switch sensor so it is to the left, opposite of flow.

50-taper spindle:

  • Oil-pump motor [1]
  • Oil Flow Switch [2]
  • Scavenge Line [3]
  • Oil Fill Hole Plug[4]
  • Oil Filter [5]
  • Oil Pump [6]
  • Oil Level Switch [7]
  • Lubrication Tube [8]
  • Oil Nozzle [9]
  • Orifice [10]
  • Oil Reservoir [11]

Part Number Callouts:

  • [1] - PN: 58-3691
  • [2] - PN: 58-3618 (Needs to be ordered)
  • [3] - PN: 59-1652
  • [4] - PN: 58-3001
  • [5] - PN: 58-1349
  • [6] - PN: 58-2259
  • [7] - PN: 58-1441
  • [8] - PN: 58-0039
  • [9] - PN: 58-3618

Symptom Table

Symptom Possible Cause Corrective Action
Alarm 4.126 GEARBOX FAULT Insufficient air volume. Make sure that air supply meets the requirements, and check for leaks.
The high or low gear status sensor is faulty. Troubleshoot the sensors.
The high or low gear solenoid is faulty. Troubleshoot the solenoid.
Damaged gearbox. Make sure the gearbox shifts when applying air to it.
Shift dampener installed. Remove the shift dampener.
Alarm 4.126 GEARBOX FAULT intermittently generated on machines built with a digital SMC gearbox solenoid There is a small delay when the solenoid is commanded, thus causing the alarm to generate. Order service kits 93-3450 & 93-3452 and follow the Low Load Solenoid Valve Kit - Installation procedure.
Alarm 4.2011 LOW GEARBOX OIL LEVEL The oil level is low. Fix the leaks and refill with oil.
The NGC software is outdated.
 Starting in NGC software version 100.17.000.2045 to 100.19.000.1003 the control only monitors the gearbox oil level condition at power-on. Once the gearbox low oil condition is detected, the icon will clear on the next power on when a normal level condition is detected.  If you are getting a Low Gearbox Oil icon during machine operation, make sure you update the software to 100.17.000.2045 or higher.  Too much oil will cause a leak,  drain the oil and fill with the correct amount.

Note:  In software version 100.19.000.1102 and higher the gearbox oil level is checked continuously when the spindle fan is off.  After the spindle fan turns off, there is a delay before gearbox oil level monitoring begins.  Press the [RESET] to clear the low gearbox oil icon.
Oil level switch is faulty. Troubleshoot the oil level switch.
Anti-Siphon solenoid not working. See Solenoid/Orifice Upgrade section below.
Orifices getting clogged causing a leak. Blow air through the orifices to unclog, 
Alarm 4.2012 INSUFFICIENT SPINDLE GEARBOX OIL FLOW The oil level is low. Fix the leaks and refill with oil.
There is a clog in the oil-pump inlet screen. Clean the inlet screen.
There is a problem with the oil flow switch. Troubleshoot the oil flow switch.
The oil-pump motor does not receive power. Troubleshoot the oil-pump motor.
There is a problem with the oil-pump motor gears or coupler. Inspect the gears or coupler.
Faulty P-Tech oil pump If the machine was manufactured before August of 2019 and the gearbox oil pump is a P-Tech P/N TTM-0669, replace the oil pump.  Note:  Do not replace the P-Tech pump if the P/N does not match the one mentioned above.
Anti-Siphon solenoid not working. See Solenoid/Orifice Upgrade section below.
Orifices getting clogged causing a leak. Blow air through the orifices to unclog, 
The oil flow is low at startup of the spindle. On machines built with the flow switch at the input of the gearbox and an orifice on the oil reservoir. Perform the flow switch relocation.
A Low Gearbox Oil icon appears during machine operation. The NGC software is outdated. Starting in NGC software version 100.17.000.2045 to 100.19.000.1003 the control only monitors the gearbox oil level condition at power-on. Once the gearbox low oil condition is detected, the icon will clear on the next power on when a normal level condition is detected.  If you are getting a Low Gearbox Oil icon during machine operation, make sure you update the software to 100.17.000.2045 or higher.  Too much oil will cause a leak,  drain the oil and fill with the correct amount.

Note:  In software version 100.19.000.1102 and higher the gearbox oil level is checked continuously when the spindle fan is off.  After the spindle fan turns off, there is a delay before gearbox oil level monitoring begins.  Press the [RESET] to clear the low gearbox oil icon.
Noisy Gearbox The oil level is low. Fix the leaks and refill with oil.
The drive belts are worn or incorrectly adjusted. Set the belt tension.
The encoder feedback is faulty. See the Excessive Gearbox Noise section below.
Damaged or worn out encoder pulley or encoder belt. Inspect the encoder pulley.
Run-out or play within the encoder. Check for runout or play.
The gears are damaged. Perform a vibration analysis.
Gearbox emits loud grinding/growling noise during a cut. The drive belts are worn or incorrectly adjusted. Set the belt tension.
Noisy Gearbox after a Gearbox replacement. The gearbox may need to be broken in. Write a program to run the gearbox on high at 50% max RPM for 2 hours and then to run the gearbox on low at 50% max RPM for another 2 hours.
High Load Bad connection at the Wye/Delta contactor. Troubleshoot Wye/Delta assembly.
Gearbox Oil Leaks through the main output shaft. Anti-Siphon solenoid not working. See Solenoid/Orifice Upgrade section below.
Spindle motor temperature sensor fluctuating  Electrical noise around that area. Refer to: Analog Sensors - Troubleshooting Guide - NGC 

Solenoid/Orifice Upgrade

1

Remove the solenoid [1] and the 0.010" and 0.03." orifices [2] from the oil tank assembly, and replace them with a 0.020" orifice [3] P/N 58-0297.

Install a muffler [4] P/N 58-1861 on the gearbox housing as shown on the image. 

Note: If the gearbox was equipped with a antisiphon solenoid there was a hose going to this port on the housing. 

Follow the instuctions on the reservoir decal to refill the tank.

2

PRESSURIZED OIL TANK (5PSI) FILL/TOP-OFF INSTRUCTIONS

1. Remove the fill plug and set aside.

2. Run the oil pump for one minute in MDI, M59 P21; for NGC machines.

3. If necessary, fill tank to top of fill plug with Mobil SHC627 or Mobil 1 15W-50.

4. Replace the fill plug securely and clean off all oil residue.

5. Run the spindle for 10 minutes and check for oil leaks; repair as necessary.

Drive Belts

Corrective Action:

Check for damage to the pulleys. Check the drive belts for wear and correct tension.

Low Ambient Shop Temperature

Corrective Action:

Warm up the machine by running the spindle at high speed for 10 minutes to warm up the gearbox housing and the oil.

Oil Level

 Note: Starting in NGC software version 100.17.000.2045 or higher the control only monitors the gearbox oil level condition at power-on. Once the gearbox low oil condition is detected, the icon will clear on the next power on when a normal level condition is detected.  If you are getting a Low Gearbox Oil icon during machine operation, make sure you update the software to 100.17.000.2045 or higher.

Note: After adding oil to the gearbox power cycle the machine to trigger the oil level measurment.  Adding too much oil will cause the gearbox to leak.

Corrective Action:

  • Fix the leaks.
  • Fill/Top off oil.

50 Taper Gearbox:

  1. Remove fill plug and set aside.
  2. Run spindle at 500 RPM for apprx. one minute then stop.
  3. If necessary, fill tank to top of fill plug with Mobil SHC627 or Mobil 1 15W-50.
  4. Replace fill plug securely and clean off all oil residue.

Machines with a reservoir: Add 17 oz (500 ml) of Mobil SHC 627 transmission oil to the reservoir. Some machines have the reservoir near the spindle fan [1]. Other machines have the reservoir mounted on the sump tank [2]. Remove the spindle head covers to get access to it.

 Caution: Do not add more than 500 ml of oil at a time. The plastic reservoir wil completely empty the oil into the gearbox.

Oil Flow Switch

Note: Starting in NGC software version 100.17.000.2045 or higher the control only monitors the gearbox oil level condition at power-on. Once the gearbox low oil condition is detected, the icon will clear on the next power on when a normal level condition is detected.  If you are getting a Low Gearbox Oil icon during machine operation, make sure you update the software to 100.17.000.2045 or higher.  Too much oil will cause a leak,  drain the oil and fill with the correct amount.

Proximity Senor Oil Flow Switch:
  1. Fittings
  2. Retention clip
  3. Steel ball
  4. Oil flow sensor housing
  5. Proximity sensor

Corrective Action:

Remove the oil flow sensor from the oil-pump assembly. Use a screw driver to manually operate the switch. Navigate to the I/O tab in DIAGNOSTICS. Make sure the diagnostic bit for Low Lube Press. changes from 0 to 1.

 Note: The name of this diagnostic bit in older software versions is Low GB Oil Flow.

If the diagnostic bit for Low Lube Press. does not change from 0 to 1, disconnect the oil flow sensor from the connector bracket. Put an electrical jumper across the (2) pins in the connector for the oil flow sensor [1]. Make sure the diagnostic bit for Low Lube Press. changes from 0 to 1. If the input changes, the oil flow proximity sensor is faulty.

If the diagnostic bit for Low Lube Press. does not change from 0 to 1, disconnect the cable from the P12 connector [2] on the I/O PCB. Put an electrical jumper across pins 2 and 3 of the P12 connector. Make sure the diagnostic bit for Low Lube Press. changes from 0 to 1. If the input changes, the 950 cable is defective. If the input does not change, troubleshoot the I/O PCB.

Oil Pressure Switch

Corrective Action:

Make sure the pressure switch connection is clean and well seated.

Use a voltmeter to check the continuity of the pressure switch when the pump is running. If the switch is open (O.L.) when there is pressure in the system, replace it.

Check the pressure switch with a voltmeter when the pump is running. If the switch is open (O.L.) when there is pressure in the system, replace it.

Oil Level Switch

 Note: Starting in NGC software version 100.17.000.2045 or higher the control only monitors the gearbox oil level condition at power-on. Once the gearbox low oil condition is detected, the icon will clear on the next power on when a normal level condition is detected.  If you are getting a Low Gearbox Oil icon during machine operation, make sure you update the software to 100.17.000.2045 or higher.  Too much oil will cause a leak,  drain the oil and fill with the correct amount.

Corrective Action:

Remove the oil-level switch from the gearbox. While you move the float from position [2] to position [1], measure for continuity across pins 2 and 4 of the connector for the oil-level switch.The oil-level switch operates correctly when:

  • There is not continuity when the magnet is at position [2].
  • There is continuity when the magnet is at position [1].

Replace the oil-level switch if it does not operate correctly.

Disconnect the 950 cable from the P12 connector on the I/O PCB. Measure for continuity across pins 1 and 3 of the connector for the oil-level switch on the 950 cable. If there is continuity, there is a short circuit in the 950 cable. Replace the cable.

Put an electrical jumper across pins 1 and 3 of the P12 connector. Press [PARAM/DGNOS] twice. Navigate to the I/O tab. Make sure the diagnostic bit for Low GB Oil Level changes from 1 to 0. If the input does not change, troubleshoot the I/O PCB.

Oil Filter

Corrective Action:

Put a wrench [2] on the straight male-fitting [1] to make sure it does not move. With another wrench [3], turn the hose and the barbed fitting [4] counterclockwise to remove them.

Put a wrench [6] on the inlet-screen housing [5] to make sure it does not move. With another wrench [7], turn the straight male-fitting [8] counterclockwise to remove it.

Remove the spring [1] and the inlet screen [2] from the inlet-screen housing [3]. Clean the inlet screen [4]. Reinstall the inlet screen.

Oil-Pump Motor

Corrective Action: Troubleshoot the oil-pump motor.

Command the spindle to operate.

 Note: There is a voltage output to the gearbox oil pump when the spindle operates.

Monitor the motor fan on the gearbox oil pump. If the motor fan on the gearbox oil pump does not operate, make sure the oil pump receives the correct voltage. Use a multimeter with needle-tip probes to measure the voltage across the cable connector for the gearbox oil pump.

 Note: Do not measure the voltage with the oil pump cable disconnected from the 300A cable.

The measured voltage must be 120 VAC. If the voltage is correct and the pump does not operate, go to Section 6.

If the voltage is not correct, make sure the voltage output from the I/O PCB is correct. Use a multimeter with needle tip test probes to measure the voltage between pin 1 and pin 2 on the 300A-cable connector at P41 (Classic Haas Control) or P32 (Next Generation Control) on the I/O PCB.

 Note: Do not measure the voltage with the 300A cable disconnected from the P41 connector on the I/O PCB.

The measured voltage must be 120 VAC. If the measured voltage is correct, the 300A cable is defective. If there is no voltage output, refer to these troubleshooting guides:

Wye/Delta Contactor

A worn contactor can send unreliable power to the gearbox motor, which can cause a high load. Check the connections at the Wye/Delta contactor. Make sure the terminals are tight.

Corrective Action:

Refer to Wye-Delta Contactor - Troubleshooting Guide to troubleshoot the Wye/Delta connectors.

Excessive Gearbox Noise

Corrective Action:

Determine if the problem is mechanical or electrical by commanding the spindle rpm where the noise is heard and then turning off the power.

If the noise goes away this means that the cause of the noise may be the encoder feedback.   

Damaged gears in the gearbox can cause excessive noise. Contact your local HFO for a vibration analysis to see if the gears are damaged.

Gearbox

Corrective Action:

Manually actuate the High/Low gear solenoid and slowly turn the spindle by hand. The gearbox should shift and the Hi Gear and Low Gear bits on the diagnostic page should change state.

If the gearbox does not shift, it may have internal damage.

If the gearbox shifts, refer to these troubleshooting guides for the high and low gear solenoids and the I/O PCB.