57 l/min tractor hydraulic tests - Low flow rate system


The low flow rate system supplies:
- the steering spool valve;
- the Power Shuttle,
- the Speedshift and its control or the Dyna-4 gearbox;
- the Power Shuttle hydraulic control unit;
- the Hare / Tortoise mechanism located at the rear right-hand side of the gearbox (Speedshift only);
- the 4WD unit located in the lower part of the centre housing;
- the front and rear differential locks;
- the PTO clutch located at the front of the centre housing;
- the PTO brake located in the top cover plate at the back of the centre housing.
An additional function ensures the lubrication of mechanical components and maintains the level in the brake master cylinders (except Meritor).

Checking the flow rate of the pump
When carrying out tests, the rear axle must not be placed on chocks with the front axle (4WD) engaged.
- Connect a flowmeter between the 15 micron filter(s) (1) outlet located to the front right-hand side of the rear axle, and the supply hose (2) to the Orbitrol spool valve. Check that the flowmeter load valve remains fully open throughout the test.


- Also connect a pressure gauge to the low pressure diagnostics connector (1) screwed to the top of the right-hand hydraulic cover plate, at the front.


- Check Q3.

Engine speed (rpm)        P4 (bar)     Q3 (l/min)      Correct position
          1000                       18 ±1         16.0± 1          steering at neutral
          2200                       18 ±1         32.7± 2          steering at neutral

Checking for leaks at clutches and slave devices
To adjust reference flow rate Q4:
- all low pressure functions should be at neutral;
- the front axle should be engaged (clutch not supplied, indicator light on);
- the range lever should be in Tortoise position (icon);
- the reverse shuttle control should be in neutral position;
- Speedshift version:
- Speedshift should be in D range;
- Dyna-4 version:
- The Dyna-4 should be in C range;
- The differential lock should be disengaged (indicator light off),
- the power take-off should be disengaged (indicator light off).


Check 


The flowmeter can be connected:
- either to the cooler outlet;
- or where the pipe joins the hose on the right-hand side of the tractor.
- The flowmeter should be connected using makeshift unions.
- Connect the flowmeter as required (see previous remark).
- Connect a pressure gauge set to approximately 30 bar to the low pressure connector (1).
- Note the Q4 reference flow rate at 1000 rpm.
- Activate each function separately and note the Q5 flow rate.
- The difference Q4 - Q5 represents the leak detected.

The value read should not exceed the values indicated in the "Identifying leaks at clutch and slave devices" table below. Examples of the test on the PTO clutch.
Example 1
Q4 = 15 l/min Q5 = 14.5 l/min
leak detected = 0.5 l/min
Conclusion: Test OK
Example 2
Q4 = 15 l/min Q5 = 13 l/min
leak detected = 2 l/min

Conclusion: Leak exceeds permissible value
- Before checking the following function and to avoid misreading the Q5 flow rate, bring the control of the component tested back to the neutral position or to the above neutral positions. When all clutch and slave devices are activated, the low pressure P4 should remain at 18 ± 1 bar. The leaks in the single control systems can be detected according to the values in the table. For the differential lock function, an additional test is necessary to determine the difference between the front and rear.

Checking method
- Disconnect and block one of the piston supplies.
- Check if the leak is still present.


Supply to the steering spool valve


- Connect a pressure gauge fitted with a coupler, ref. 3582045M1 to the diagnostics connector (1) of the right-hand hydraulic cover plate.
- Turn the steering to full lock and check that: P5 = 170 bar at 1000 rpm and at 2200 rpm.

Supply to the steering ram

Check
- Connect a pressure gauge bypass to each hose of the steering ram.
- With steering at neutral, check that P6 = 18 bar.
- Turn the steering wheel.


Pressure P6 should be:
- between 18 and 170 bar at the ram supply side;
- 18 bar in the return line.

Checking for leaks in the steering system
- Run the engine at 1000 rpm.
- Turn the steering on full lock and apply a torque of
4 Nm to the steering column. The steering wheel must not turn more than 2 rpm. If the steering wheel turns more than 2 rpm, disconnect the pipes that supply the rams, block the two ports and then apply the same torque (4 Nm) to the steering wheel. If it turns at less than 2 rpm, there is a leak at the ram. Checking the supply pressure of the Power Shuttle control unit

Speedshift version


- Connect a pressure gauge with a capacity of approximately 30 bar to the diagnostics connector (1) of the control unit located at the front right of the gearbox.
- Check P7.

Engine speed (rpm)              P7 (bar)
           1000                            18 ± 1
           2200                            18 ± 1

Dyna-4 version
- Connect a pressure gauge with a capacity of approximately 30 bar to the diagnostics connector (1) of the control unit located at the front right of the gearbox.


- Check P7.

Engine speed (rpm)             P7 (bar)
           1000                            18 ± 1
           2200                            18 ± 1

Checking the pressure of the Power Shuttle (forward and reverse) clutches

Speedshift version
To keep the tractor stationary, ensure that the transmission lever is in neutral.
- The diagnostics connectors (1) (forward) and (2) (reverse) of the Power Shuttle clutches are on the control unit fitted to the front right of the gearbox.


- The Power Shuttle control lever is located to the left beneath the steering wheel:
- lever in upward position: forward travel (the letter F is displayed on the instrument panel);
- lever in downward position: reverse travel (the letter R is displayed on the instrument panel).


Check 
- Connect a pressure gauge with a capacity of approximately 30 bar to each diagnostics connector (1) and (2).
- Run the engine at 1000 rpm.
- Activate the lever to select the direction (forward / reverse) and the neutral position.
- Check P8 and P9.
                       
          Lever position           Forward clutch (1) P8 (bar)      Reverse clutch (2) P9 (bar)
              Forward                            18 ± 1                                        0
    Neutral or de-clutched                      0                                           0
              Reverse                                0                                        18 ± 1

Checking the pressure of the Power Shuttle (forward and reverse) clutches

Dyna-4 version
The diagnostics connectors (1) (forward) and (2) (reverse) of the shuttle clutches are on the control unit fitted to the front right of the gearbox as shown in figure. The Power Shuttle control lever is located to the left beneath the steering wheel:
- lever in upward position: forward travel
- lever in downward position: reverse travel


Check 
- Connect a pressure gauge with a capacity of approximately 30 bar to each diagnostics connector (1) and (2).
- Run the engine at 1000 rpm.
- Activate the lever to select the direction (forward / reverse) and the neutral position.
- Check P8 and P9.

Lever position           Forward clutch (1) P8 (bar) GTA2520     Reverse clutch (2) P9 (bar)  GTA2520
Forward                                              20 ± 1                                                         0
Neutral or de-clutched                             0                                                             0
Reverse                                                 0                                                         20 ± 1

Checking the lubrication pressure of the Power Shuttle clutches (forward and reverse) (Speedshift version only)
- These clutches are lubricated by a gear pump that is independent from that used for the standard lubrication system.
- This pump has two additional spools which act as valves and are fitted in the front cover plate of the Power Shuttle. They thus lubricate the reverse position.
- The check is carried out with the assistance of an operator positioned in the operator's seat.

Check
- Connect a pressure gauge with a capacity of approximately 11 bar to the diagnostics connector (1) located at the front right of the gearbox.


- Check P10 as indicated in the table.
           
Lever position             Engine speed (rpm) P10 (bar)     Pedal engaged      Pedal disengaged
Forward ratio (letter F)                  1000                             0.5 ± 0.1               1.5 ± 0.1
                                                      2200                             0.9 ± 0.1                2.0 ± 0.1
Neutral                                          1000                             1.5 ± 0.1                1.5 ± 0.1
                                                      2200                             2.0 ± 0.1                2.0 ± 0.1
Reverse ratio (letter R)                  1000                             0.4 ± 0.1                1.5 ± 0.1
                                                      2200                             0.8 ± 0.1                 2.0 ± 0.1

Checking the pressure on the Speedshift supply line
- Run the engine at 1000 rpm.
- Connect a pressure gauge with a capacity of approximately 30 bar to the low pressure diagnostics connector (1) screwed into the upper part of the right-hand hydraulic cover plate.
- Measure the pressure: P4 = 18 bar ± 1 bar


Checking the dry clutch pressure (Speedshift version only)
The pressure can reach 30 bar when the pedal is pressed down; it is therefore necessary to connect the pressure gauge after starting the engine.
- Connect a pressure gauge with a capacity of 30 bar fitted with a coupler ref. 3582045M1 to the diagnostics connector (1) located on the right-hand side of the gearbox.
- Run the engine at 1000 rpm.
- Measure the pressure:


P8 = 1.5 bar maximum clutch engaged
P8 = 13-15 bar clutch disengaged: new disc

P8 = 18-20 bar clutch disengaged: worn disc