446B Backhoe Loader Transmission (Autoshift) Caterpillar

Use the following assembled hose group to perform your tests.

1. Install one 6V-4143 Coupler onto each end of 6V-3014 Hose Assembly .

2. Install one 6V-3989 Unvalved Nipple onto each pressure gauge.

3. Connect one of the 6V-3014 Hose Assembly to each of the pressure gauges.

4. Some of the 6V-3965 Fitting As must be installed into the transmission.

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Sudden movement of the machine or release of oil under pressure can cause injury to persons on or near the machine. To prevent possible injury, perform the procedure that follows before the test is done.

Note: For all tests, the machine must be at operating temperature.

The following components must be removed before the transmission system can be tested.

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Illustration 1	g00759467

1. Remove ten bolts (2) and cover (1) .

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Illustration 2	g00759476

2. Remove two bolts (3) and plate (4) .

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Illustration 3	g00759478

3. Remove two bolts (5) and plate (6). Remove floormat (7) .

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Illustration 4	g00759487

4. Remove four bolts (8) and set the floorplate (9) aside.

5. Proceed to the appropriate test that is required. Reinstall the plates, screws and the mats to the cab when testing is completed.

Test for the Torque Converter

The test will show if engine performance is good. The test will show if the torque converter operates properly. Also, the test will show if there is oil flow through the oil cooler.

Note: Any unusual noises during this check should be noted. Loud noises could indicate that repairs are needed.

1. Install the 6V-3121 Multitach on the engine. The multitach can measure engine speed by the use of a photo pickup and reflective tape. The Special Instructions, SEHS7807 has instructions for the use of the multitach.

2. Place the speed/direction control lever in NEUTRAL and engage the parking brakes. Start the engine and run the engine at low idle. Allow the engine to reach normal operating temperature.

3. Lower the stabilizers and lift the rear wheels about 150 mm (6 inch) off the ground.

4. Place the bucket hydraulic controls in the lowering position. Lift the front wheels about 150 mm (6 inch) off the ground.

5. Ensure that high idle rpm and low idle rpm are correct. Refer to the literature for the specific engine that is installed in the machine.

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NOTICE
To ensure that the transmission oil does not overheat, do not keep the torque converter in a full stall condition for more than 30 seconds. After the torque converter stall test, reduce the engine speed to low idle. In order to cool the oil, move the transmission control to the NEUTRAL position and run the engine between 1200 rpm and 1500 rpm.

6. Run the engine at high idle. Disengage the parking brakes and fully engage the service brakes. Run the transmission at normal operating temperature 59 to 71°C (138 to 160°F). Shift the speed/direction control lever to FOURTH SPEED FORWARD and stall the torque converter until the converter temperature reaches 90 to 93°C (194 to 200°F). The stall speed should be 1910 ± 75 RPM.

   Note: Do not keep the torque converter in a stall condition for very long periods of time. The torque converter, the engine, and the brakes will get hot.

7. If the stall RPM is incorrect, check that the high idle RPM and the low idle RPM are within the specification. Perform the test again if any adjustments are made.

8. If the high idle RPM and the low idle RPM are within the specification and the stall RPM is not within the specification, the stall RPM should be checked by using the other speed ranges.
   • If the high idle RPM and the low idle RPM are within the specification and the stall RPM is consistent between speed ranges, a problem with the torque converter should be suspected.

   • If the high idle RPM and the low idle RPM are within the specification and the stall RPM is inconsistent between speed ranges, a problem with the transmission clutches should be suspected.

9. When the test is complete, put the speed/direction control lever in NEUTRAL. Engage the parking brake. Stop the engine and remove the test equipment.

Problem

The oil gets too hot during normal operation.

Probable cause

1. Not enough oil is in the torque converter because the inlet relief valve for the torque converter is open.

2. The oil pump fails.

3. The torque converter fails.

4. The temperature gauge is bad. Replace the temperature gauge and the sending unit.

5. The air flow to the oil cooler is blocked with debris. Debris could also be blocking air flow to the engine cooler.

Transmission Tests

This section contains a complete list of the pressures for each combination of speed and direction. This section also contains the pressures for the other pressure taps.

The following illustration shows the location of the pressure taps that are used on the power shift transmission.

Illustration 5	g00809642
Location of pressure taps (1) Clutch pressure for the all wheel drive (If equipped) (2) Pressure for speed clutch 1 (3) Reverse clutch pressure (4) Forward low pressure (5) Forward high pressure (6) Lube pressure (7) Regulated pump pressure (8) Pressure for speed clutch 2 (9) Pressure for speed clutch 3

Note: When the pressures are checked at high idle, the transmission will drive through the service brakes and the parking brakes when the transmission is in the low speed ranges. The clutch pressures at high idle should be taken while the wheels are raised off the ground.

Note: In order to check the FIFTH SPEED FORWARD pressure, raise the rear wheels off the ground and disengage the all wheel drive (if equipped). In order for FIFTH SPEED FORWARD to engage, the ground speed of the machine must reach a preset speed.