D6D TRACTOR POWER TRAIN – Testing And Adjusting

Troubleshooting – (Power Shift)

Use this as a reference for the location and correction of problems in the power train. When more checks are necessary, use the 5P6225 Transmission Hydraulic Test Group. Locations of the pressure taps and procedures for testing and adjusting are given in the D6D POWER SHIFT TRANSMISSION TESTING AND ADJUSTING, Form No. SENR7440.

Always make visual checks first. Then check the operation of the machine and go on to check with the instruments.

Visual Checks

1. Check the oil levels of the transmission and the steering clutch and bevel gear case.

2. Check the oil level in the final drives.

3. Check all oil lines, hoses and connections for leaks and damage. Look for oil on the ground under the machine.

4. Check the control linkages for the transmission, steering clutches and brakes for damage and/or adjustment.

5. Check the adjustment of the track.

6. Let the oil out of the filter housing. Remove and check the filter element for foreign materials. Check the magnetic screen and the screen in the bottom of the engine flywheel housing.

a. Bronze-colored particles give an indication of a clutch failure.
b. Shiny steel particles give the indication of a pump failure.
c. Rubber particles give an indication of a seal or hose failure.
d. Aluminum particles give an indication of a torque converter failure.

If you find metal or rubber particles, all components of the transmission hydraulic system must be washed clean. Do not use parts with damage. Use new parts.


Checks During Operation

With the engine running, move the transmission selection lever to all speed positions. The detents must be felt in all positions.

Operate the machine in each direction and in all speeds. Make note of all noises that are not normal and find their sources. If the operation is not correct, make reference to the CHECK LIST DURING OPERATION for “problems” and “probable causes”.


Check List During Operation

Transmission

Problem: Transmission does not operation in any speed or does not engage (slips) in all speeds.

PROBABLE CAUSE:

1. Low oil pressure caused by:

a. Low oil level.
b. Control linkage loose or adjustment not correct.
c. Failure of the oil pump or the pump drive.
d. Air leaks on inlet side of pump.
e. Safety valve not moving.
f. Leakage inside the transmission.
g. Adjustment of the pressure relief valve not correct, or valve does not close.
h. Load piston or pressure differential valve not moving.
2. Mechanical failure in transmission.
3. Failure of torque converter.
4. Bevel pinion and/or bevel gear failure.
5. Failure in steering clutches.
6. Failure in final drives.

Problem: Transmission does not make a shift.

PROBABLE CAUSE:

1. Control linkage loose or adjustment not correct.
2. Low oil level.
3. Low clutch pressures.

Problem: Slow shifts.

PROBABLE CAUSE:

1. Low oil pressure.
2. Adjustment of control linkage not correct.
3. Air leaks on inlet side of pump.
4. Load piston or pressure differential valve not moving.

Problem: Transmission downshifts on its own when machine is in operation.

PROBABLE CAUSE:

1. Loss of oil pressure causes safety valve to move controls toward neutral position.

Problem: Transmission engages very suddenly (rough shifts).

PROBABLE CAUSE:

1. Initial setting of the pressure modulating valve not correct.
2. Adjustment of control linkage not correct.
3. Load piston or pressure differential valve do not move.
4. Valve springs that are weak or have damage.

Problem: Transmission operates in Forward speeds only.

PROBABLE CAUSE:

1. Control linkage loose or adjustment not correct.
2. No. 2 clutch not engaged (slips) because of:

a. Low oil pressure.
b. Discs and plates have too much wear.
c. Clutch has broken parts.

Problem: Transmission operates in Reverse speeds only.

PROBABLE CAUSE:

1. Control linkage loose or adjustment not correct.
2. No. 1 clutch not engaged (slips) because of:

a. Low oil pressure.
b. Discs and plates have too much wear.
c. Clutch has broken parts.

Problem: Transmission does not operate in First speed Forward or Reverse.

PROBABLE CAUSE:

1. No. 5 clutch not engaged (slips) because of:

a. Low oil pressure.
b. Discs and plates have too much wear.
c. Clutch has broken parts.

Problem: Transmission does not operate in Second speed Forward or Reverse.

PROBABLE CAUSE:

1. No. 3 clutch not engaged (slips) because of:

a. Low oil pressure.
b. Discs and plates have too much wear.
c. Clutch has broken parts.

Problem: Transmission does not operate in Third speed Forward or Reverse.

PROBABLE CAUSE:

1. No. 4 clutch not engaged (slips) because of:

a. Low oil pressure.
b. Discs and plates have too much wear.
c. Clutch has broken parts.

Problem: Transmission is in a speed when the selection lever is in Neutral.

PROBABLE CAUSE:

1. Control linkage loose or adjustment not correct.
2. Direction clutch is engaged and does not release.

Problem: Transmission engages but the machine does not move and the engine stops.

Probable Cause:

1. Failure in final drives.
2. Failure in steering clutches.
3. Failure in bevel gear and pinion.
4. Gears in the transmission will not move because of:

a. Too many clutches are engaged.
b. Mechanical failure in transmission.
5. Mechanical failure in torque divider or converter.

Problem: Transmission gets hot.

PROBABLE CAUSE:

1. Low oil level.
2. High oil level.
3. Core of oil cooler not completely open.
4. Low oil flow as a result of pump wear.
5. Long periods of operation with converter at or near stall speed.
6. Too much resistance between the plates and discs of the clutches when not engaged.

Problem: Pump noise not normal.

PROBABLE CAUSE:

1. Loud sounds at short intervals that give an indication that particles are going through the pump are caused by pump cavitation.
2. A constant loud noise is an indication of pump failure.
3. Air at the inlet side of the pump (aeration).

Torque Converter

Problem: Torque converter gets hot.

PROBABLE CAUSE:

1. Bad temperature gauge.
2. Mechanical failure in torque converter.
3. Core of oil cooler not completely open.
4. Long periods of operation with converter at or near stall speed.
5. Too much oil leakage in torque converter. (Oil fills the engine flywheel housing and torque divider housing).
6. Too much restriction in oil cooler lines.
7. Not enough oil to torque converter because of:

a. Oil pump failure.
b. Too much oil leakage in transmission.
c. Inlet relief valve not operating correctly.

Torque Divider

The information that follows must be used to diagnose troubles in the torque divider. This information does not give every possible trouble, however, many of the common troubles are given.

Problem: Torque divider gets hot.

PROBABLE CAUSE:

1. Air in oil system.

a. Vents for system not open.
b. Loose oil line connections.
c. Loose oil filter cover.
2. Low oil pressure.

a. Leakage around torque converter seals.
b. Oil line between inlet relief valve and torque converter has restrictions.
c. Inlet relief valve not closing.
d. Outlet relief valve not closing.
e. Low oil level.
f. Bad torque divider oil pump.
3. Defects in cooling system.

a. Low coolant level.
b. Loose fan belts.
c. Bad water pump.
d. Oil cooler core not open.
e. Restrictions in oil cooler lines.
4. Operation in high altitudes.
5. Operation in high outside temperatures.
6. Long periods of operation with the torque converter at or near stall speed.
7. Bad temperature gauge.
8. Transmission not in the correct speed for the load on the machine.

Problem: Loss of oil.

PROBABLE CAUSE:

1. Connections.

a. Tubes.
b. Hoses.
2. Torque divider oil pump.

a. Leakage around cover gasket.
3. Seals.

a. Impeller to carrier seals.
b. Front bearing retainer to carrier seals.
c. Oil seal or torque divider output shaft.
4. Gaskets.

a. Flywheel housing to torque divider housing.
b. Seal and bearing carriers.
c. Flywheel housing to engine block.

Problem: High inlet pressure.

PROBABLE CAUSE:

1. Inlet relief valve will not open.
2. Restrictions in outlet relief valve.
3. Spring in outlet relief valve too strong (will not release).
4. Restrictions in outlet line to oil cooler.

Problem: Low inlet pressure.

PROBABLE CAUSE:

1. Bad transmission or torque divider oil pump.
2. Not enough inlet oil.
3. Inlet relief valve.

a. Dirt or foreign material will not let valve close.
4. Outlet relief valve.

a. Spring too weak.
b. Dirt or foreign material will not let valve close.
5. Seal leakage.

a. Impeller to carrier seals.
b. Front bearing retainer to carrier seals.

Problem: Noises in torque converter that sound like metal in contact.

PROBABLE CAUSE:

1. Bearings that have too much wear or damage.
2. Loose turbine, impeller or stator blades.
3. Too much side load on output shaft.

Problem: Too much oil in engine flywheel housing and torque divider housing.

PROBABLE CAUSE:

1. Bad torque divider oil pump.
2. Inlet screen for oil pump not open.
3. Too much leakage inside the torque converter.

Problem: Noise in planetary gears of torque divider.

PROBABLE CAUSE:

1. Failure of bearings for planetary gears.
2. Failure of gear teeth.
3. Failure of bearing in flywheel.

NOTE: Check for leakage in the torque divider when the oil is at the normal temperature of operation.


Steering

Problem: Machine will not turn in one direction.

PROBABLE CAUSE:

1. Adjustment of steering control linkage not correct.
2. Too much leakage in steering clutch control valve.
3. Steering clutch discs or plates have wear or damage.
4. Seals of steering clutch piston have damage.

Problem: Machine will not turn in either direction.

PROBABLE CAUSE:

1. Low oil pressure to steering clutch control valve.
2. Leaks in control valve.
3. Adjustments of control linkages for the steering clutches and brakes not correct.
4. Steering clutch or clutches not releasing.

Problem: Machine moves in either direction when both steering clutches are engaged.

PROBABLE CAUSE:

1. Adjustments of the control linkages for the steering clutches and brakes not correct.
2. Steering clutch discs or plates have wear or damage.
3. Steering clutch springs that are weak or have damage.
4. Bolts that hold the steering clutch springs are broken.
5. Splines on the steering clutch hubs have damage.
6. Weak or broken springs in control valve.

Problem: Slow steering.

PROBABLE CAUSE:

1. Control linkages for the steering clutches and brakes loose or adjustment not correct.
2. Brake linings have wear or damage.
3. Low oil pressure to steering clutch control valve.
4. Splines on steering clutch hubs have damage.
5. Leaks in steering clutch control valve.

Troubleshooting – (Direct Drive)

Use this as a reference for the location and correction of problems in the power train. When more checks are necessary, use the 5P6225 Transmission Hydraulic Test Group. Locations of the pressure taps and procedures for testing and adjusting are given in the HYDRAULIC SYSTEM (Direct Drive) TESTING AND ADJUSTING in this manual.

Always make visual checks first. Then check the operation of the machine and go on to check with the instruments.

Visual Checks

1. Check the oil levels of the flywheel clutch, transmission and bevel gear case.

2. Check the oil levels of the final drives.

3. Check all oil lines, hoses and connections for leaks or damage. Look for oil on the ground under the machine.

4. Check the control linkages for the flywheel clutch, .transmission, steering clutches and brakes for damage and/or adjustment.

5. With the flywheel clutch not engaged, turn the universal joint by hand. It must turn freely. If the oil is cold, the universal joint will be harder to turn. If the universal joint does not turn, disconnect it from the flywheel clutch. Turn the universal joint again and see if the gears in the transmission turn.

6. Check the magnetic screen, oil filter and screen in engine flywheel housing for foreign materials.

If you find metal or rubber particles, all components of the transmission hydraulic system must be washed clean. Do not use parts with damage. Use new parts.


Checks During Operation

With the engine running, move the control levers for the transmission to all speed positions and the control lever for the flywheel clutch to all positions.

Operate the machine in each direction and in all speeds. Make note of all noises that are not normal and find their sources. If the operation is not correct, make reference to the CHECK LIST DURING OPERATION for “problems” and “probable causes”.


Check List During Operation

Transmission

Problem: Transmission does not operate in any speed or is not engaged (slips) in all speeds.

PROBABLE CAUSE:

1. Failure in flywheel clutch.
2. Mechanical failure in transmission.
3. Failure of bevel gear.
4. Failure in steering clutches.

Problem: Transmission operates in reverse speeds only or forward speeds only.

PROBABLE CAUSE:

1. Control linkage loose or adjustment not correct.
2. Mechanical failure in transmission.

Problem: Transmission does not make a shift.

PROBABLE CAUSE:

1. Control linkage loose or asjustment not correct.
2. Mechanical failure in transmission.

Problem: Transmission does not remain in a speed when under load conditions.

PROBABLE CAUSE:

1. Interlock linkage adjustment not correct.
2. Interlock linkage has damage.
3. Inerlock linkage spring is broken.
4. Ends of interlock plungers and/or notches in shift shafts have wear.
5. Interlock springs are weak or have damage.

Problem: Shifts of the transmission are not easy.

PROBABLE CAUSE:

1. Shift forks have damage or wear.

Problem: Gears in the transmission do not turn.

PROBABLE CAUSE:

1. Failure of the bearings on one or more of the shafts.
2. Gear in transmission is broken.
3. One or more of the gears not correctly engaged (transmission in two speeds at the same time).

Problem: Transmission is in a speed when the control lever is in neutral.

PROBABLE CAUSE:

1. Control linkage loose or adjustment not correct.
2. Mechanical failure in transmission.

Problem: Transmission gets hot.

PROBABLE CAUSE:

1. High oil level.
2. Low oil flow because of a pump that has wear or leaks in the lubrication system.
3. Low oil level.

Problem: Pump noise not normal.

PROBABLE CAUSE:

1. Loud sounds at short intervals that give an indication that particles are going through the pump are caused by pump cavitation.
2. A constant loud noise is an indication of pump failure.
3. Air at the inlet side of the pump (aeration).

Steering

Problem: Machine will not turn in one direction.

PROBABLE CAUSE:

1. Adjustment of steering control linkage not correct.
2. Too much leakage in steering clutch control valve.
3. Steering clutch discs or plates have wear or damage.
4. Seals of steering clutch piston have damage.

Problem: Machine will not turn in either direction.

PROBABLE CAUSE:

1. Low oil pressure to steering clutch control valve.
2. Adjustment of the relief valve not correct.
3. Leaks in relief valve or control valve.
4. Adjustments of control linkages for the steering clutches and brakes not correct.
5. Steering clutch or clutches not releasing.

Problem: Machine moves in either direction when both steering clutches are engaged.

PROBABLE CAUSE:

1. Adjustments of the control linkages for the steering clutches and brakes not correct.
2. Steering clutch discs or plates have wear or damage.
3. Steering clutch springs that are weak or have damage.
4. Bolts that hold the steering clutch springs are broken.
5. Splines on the steering clutch hubs have damage.

Problem: Slow Steering.

PROBABLE CAUSE:

1. Control linkages for the steering clutches and brakes loose or adjustment not correct.
2. Brake linings have wear or damage.
3. Low oil pressure to steering clutch control valve.
4. Splines on steering clutch hubs have damage.
5. Leaks in steering clutch control valve.

Hydraulic System – (Direct Drive)

TRANSMISSION AND STEERING CLUTCH OIL SYSTEM SCHEMATIC (Direct Drive)

1. Hydraulic control mechanism for left brake.

2. Relief valve for steering clutch controls.

3. Oil filter.

4. Oil pump.

5. Hydraulic control valve for the steering clutches.

6. Oil cooler.

7. Hydraulic control mechanism for right brake.

8. Transmission case.

9. Reservoir in steering clutch and bevel gear case.

10. Transmission lubrication regulation valve.

11. Magnetic screen.

12. Scavenge pump.

13. Flywheel clutch housing.

A. Transmission oil pump.

B. Left steering clutch piston.

C. Right steering clutch piston.

D. Left brake booster.

E. Right brake booster.

F. Transmission lubrication.

G. Transmission oil pump.

------ WARNING! ------

When tests are to be done in a closed area, activate the brakes and use blocks to stop movement of the machine. Let only approved personnel on the machine. Keep other personnel off the machine and in view of the operator.

--------WARNING!------

The hydraulic system has a common reservoir. It gives lubrication oil for the bevel gear and pinion and transmission and cooling oil for the flywheel clutch, steering clutches and brakes. It also gives pressure oil for the operation of the hydraulic controls for the steering clutches and brakes.

Tests of the hydraulic system can be done with the use of pressure gauges or the 5P6225 Transmission Hydraulic Test Group.

NOTE: All tests and adjustments must be made with the oil in the hydraulic system at normal temperature of operation. Make sure the adjustments of the brake linkage and steering clutch linkage are correct. Make sure oil level in the hydraulic system is correct. The high and low idle engine speeds for this machine are given in the RACK SETTING CHARTS.

LOCATION OF PRESSURE TAPS
A. Pressure tap for transmission oil pump (at relief valve).

LOCATION OF PRESSURE TAPS
C. Pressure tap for right steering clutch. E. Pressure tap for right brake booster.

LOCATION OF PRESSURE TAPS
G. Pressure tap for transmission oil pump (at filter).

LOCATION OF PRESSURE TAPS
B. Pressure tap for left steering clutch. D. Pressure tap for left brake booster.

LOCATION OF PRESSURE TAPS
F. Pressure tap for transmission lubrication.

RELIEF VALVE FOR THE HYDRAULIC CONTROLS FOR THE STEERING CLUTCHES AND BRAKES
9. Relief valve. 20. Spacers.

Spacers (20) can be added or removed to relief valve (9) to get the correct pressure at taps (A) or (G).

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