The simplest is time delay test.
When the engine is idling, when the drive mode selector lever is set to the "D" or "R" position from the neutral position, there should be a time delay before the operation is felt. The purpose of this test is to check the operability of the gearbox components and mechanisms.
For safety reasons and to prevent breakdowns, it is necessary:
- before carrying out the test, warm up the gearbox well; the temperature of the automatic transmission should be at least 50-80°C;
- to achieve high quality testing, it is necessary to carry out at least three measurements and determine their average value;
- to maintain high performance of the automatic transmission, take one-minute breaks between measurements.
The time delay test is performed as follows.
1. Fully raise the parking brake lever.
2. Start the engine.
3. Check the engine idle speed in the "N" range. The engine idle speed should be 750-900 rpm. If the engine idle speed is not within the norm, the measurement results will also be incorrect and the test will have to be repeated.
4. Move the drive mode selector lever from the "N" range to the "D" range.
5. Use a stopwatch to measure the time from the start of the handle movement to the moment the transmission is activated. It is recommended to take measurements at least three times and determine their average value. In this case, the time delay should be no more than 1.2 s.
6. Using the same method, measure when switching from the "N" range to the "R" range. In this case, the time delay should not exceed 1.5 sec.
When evaluating the results of the test, you should assume that if there is any malfunction, the response time can only increase. Only a professional can find out the cause and fix the malfunction, so you should urgently contact the appropriate service center.
Quite simple and parking test. Its purpose is to check the performance of the engine, torque converter and gearbox as a whole.
To ensure safety and prevent breakdowns:
- it is necessary to conduct the test on a sufficiently light and wide area;
- the test must be carried out by two technicians working in pairs: one of them must observe the wheels and their stops and immediately warn about the wheels turning or the stops moving, the second must carry out the tests and record the measurements;
- the test duration should not exceed 5 seconds.
Conducting the test and evaluating its results:
1. Be sure to secure the front and rear wheels.
2. If necessary, install a tachometer.
3. Apply the parking brake.
4. Press the brake pedal with your left foot and hold it in this position throughout the test.
5. Start the engine.
6. Set the drive mode selector lever to the "D" range.
7. Press the gas pedal with your right foot all the way down and record the tachometer readings.
8. Take a break for at least one minute.
Repeat the test with the drive mode selector in the "R" range. When evaluating this test, you should know that each time you press the gas pedal, the tachometer needle should rise smoothly and stop in the range of 2400-2700 rpm. There should be no extraneous noise, vibration or impact, and the car should remain in place.
If the tachometer readings:
- less than the nominal value, but the same in both ranges ("D" and "R"), then most often the reason lies in insufficient engine power;
- above the nominal value in both ranges, then most likely the reason lies in a faulty torque converter or gearbox;
- above the nominal value in one of the ranges, then it is most likely that the fault is only in the gearbox.
The most difficult thing to conduct and evaluate is road test, which is carried out to determine the switching points, detect extraneous noises, vibrations and slippage in the gearbox.
To ensure safety, the test should be carried out on a sufficiently wide, level and empty section of road; before setting off, it is necessary to warm up the engine and gearbox well.
Conducting a "road test" and its evaluation:
1. Set the drive mode selector lever to position "D" and, gradually pressing the gas pedal, check for shifting of I-II, II-III, III-IV and IV-V gears. If there is no shifting, then the automatic transmission or its control and monitoring unit is faulty; if the switching moments are delayed, then the problem is most likely in the control system.
2. Fix the speed of 70 km/h in the "D" mode and press the gas pedal slightly. The engine speed should not change abruptly. If the tachometer shows a sharp jump in engine speed, then it can be said that the torque converter is faulty and will soon completely fail.
3. Stop and move the drive mode selector lever to the manual gear shift range. Gradually press the gas pedal, check for I-II shifting. Moving in second gear, release the accelerator pedal and check for engine braking. Repeat this operation several times, make sure that I-II and II-I shifting are not accompanied by vibration, shocks or slipping. If there are no negative phenomena, then the gearbox is in good condition.
4. Stop completely and, by moving the lever to position "1" and smoothly pressing the gas pedal, make sure that there is no switching to the second stage, and also check for engine braking when releasing the gas pedal. When repeatedly pressing and releasing the gas pedal, listen to the operation of the gearbox to detect extraneous noises and vibrations. If there is a switching to the second stage or there is no engine braking, then the control and monitoring unit is faulty.
5. Stop and, having switched to the "R" range, sharply press the gas pedal. After making sure that there is no slippage, vibration or extraneous noise, continue testing.
6. With the vehicle parked on a slope of approximately 5°, move the drive mode selector lever to position "P" and release the brake. The vehicle should lock into place; if the car rolls away, the cause should be sought in a malfunction of the gearbox parking mechanism.
We remind you that when conducting the test, you need to pay special attention to the presence of extraneous noises and vibrations. You need to treat them with due responsibility, since these noises and vibrations can be caused by imbalance of the torque converter, drive shaft, etc., which can lead to failure of the unit.
[The original source of the article is the website CHEVYMAN.ru]