Content

• Steps
• Method 1 of 2: Manual transmission
• Method 2 of 2: Automatic transmission
• Tips on how to avoid damaging your transmission
• Tips
• Warnings

The transmission of the car, starting from the engine and further, consists of: clutch, gearbox, transfer case (for 4x4 vehicles), propeller shaft, differential and wheels. This article will help you learn how to find transmission faults. The Tips section provides an overview of the symptoms and causes of problems.

Steps

Method 1 of 2: Manual transmission

1. 1 Park the vehicle with the front wheels resting on the curb. Engage first gear and release the clutch without adding gas. The engine will lose RPM and stall when the pedal is fully released. If the engine stalls abruptly at some point or the rpm drops in jerks, then the clutch is faulty. If you hear a grinding noise when you try to shift from neutral to first, the clutch is also a problem.
2. 2 Try shifting into 3rd gear and releasing the clutch when the front wheels are on the curb. If the engine does not immediately stall, then the clutch is not working at all. In this case, it is not recommended to drive this vehicle.
3. 3 Find a level, straight road to check the vehicle. Move off from the first and smoothly accelerate to the second. Shift a little later than usual, keeping the revs 500-1000 rpm more.Shift back to first gear without over-throttle. Repeat the same, shifting in 3rd gear. After reaching a speed of about 50 km / h, shift into second gear without over-throttle. No grinding noise should be heard when changing gears. A rattling noise in the box means a malfunction, and most likely the synchronizers are out of order. To make sure that it is the synchronizers that are out of order, try switching with a re-throttle, if the sound is gone, then it’s definitely a matter of them.

Method 2 of 2: Automatic transmission

1. 1 Park the car with the front wheels resting on the curb, leave the drive in gear. Add gas gradually. The car should start driving onto the curb without dropping the engine speed.
2. 2 Engage Drive and apply the brake after making sure the brake works. Press the gas pedal to the floor. The engine should not stall. If the engine stalls, it means that the clutch is not fully disengaged.
3. 3 Check the shifting smoothness. On a smooth, level road, the vehicle should accelerate evenly and without jerks. If there are points, then the box is faulty.
4. 4 Check for vibrations. After reaching 70 km / h, shift into neutral. There should not be any vibrations on either the mechanical box or the automatic one. If there are vibrations, they can occur due to the distortion of the propeller shaft or due to suspension malfunctions. Often, the distortion of the propeller shaft is felt as vibration in all directions: both vertical and horizontal, and the suspension malfunction only in one: horizontal or vertical.
5. 5 Test the steering. Try to enter a corner at 30 km / h, nothing unusual should happen. Jolting can indicate a malfunctioning differential, and will be particularly noticeable on four-wheel drive vehicles. Novice drivers Not recommended check the serviceability of the differential by pulling the car into a skid!

Tips on how to avoid damaging your transmission

• Squeeze and release the clutch fully.
• Try to smoothly engage gears, do not drop the clutch abruptly.
• Take your foot off the clutch while driving, you may inadvertently press down on it lightly, which will burn the clutch discs.
• Do not use clutch brakes on heavy trucks!
• Shift only with the clutch fully depressed
• Do not apply excessive force to the gear lever when shifting.
• RWD vehicles should avoid driving over areas where you can get caught on the underside.

Tips

• There are 3 types of gearboxes: mechanical, semi-automatic and automatic.
• Incomplete disconnection occurs when the driven disc sticks to the driver, this can be due to mechanical contamination or due to weakening of the springs.
• The most common automatic transmission malfunctions are: uneven gear shifting, incorrect gear selection, which causes the engine to call out or the car loses acceleration, gears do not engage, force is transmitted to the wheels even when neutral is engaged, or no wheel lock when the gear is engaged Parking.
• The main malfunctions of the hydraulic clutch are: incomplete opening of the discs (due to old box oil, which loses its properties), incomplete disconnection of the discs (due to lack of oil or air congestion). These problems are corrected by changing the oil, bleeding the system to eliminate air pockets, and repairing oil leaks.
• The most common transfer case problem is its dysfunction (when it does not switch between 4x4x and 2x4); if this happens, contact a car service.
• A manual transmission is a box, as its name suggests, in which you select the desired gear by moving the lever with your hand.
• Incomplete disengagement of the disks on an automatic transmission feels like a jerk forward when the box shifts, while incomplete engagement is accompanied by a roar of the engine for no apparent reason, especially when driving at speeds of 50 km / h and above.
• Incomplete engagement occurs due to wear on the clutches. Sometimes it occurs due to poor tuning of the mechanism after replacing the clutches.
• The clutch is needed to smoothly decouple the engine from the rest of the transmission.
• The automatic transmission has a so-called "hydraulic clutch". It is a combination of a hydraulic pump, which is driven by a motor, and a hydraulic motor, which is connected to the rest of the transmission. This allows oil to flow through the gearbox, even if the resistance is significantly higher than the engine can handle. An automatic transmission simplifies handling, but increases fuel consumption, increases acceleration time and does not allow the engine to brake, which can be dangerous on long descents. Hydraulic clutch is good in the city, but it shows its bad sides on long journeys.
• Gearboxes are extremely complex devices, you shouldn't try to repair them yourself! Often, the boxes are repairable, but only a qualified mechanic can understand them. If you had the knowledge necessary to repair a gearbox, you would not have to read this manual!
• If the clutch is sufficient too early or too late, then the clutch discs are worn out.
• Use the rubber sizes recommended by the manufacturer. The tread depth on rubber must be at least 5 mm (winter) and 3 mm (summer).
• If your transmission is knocked out on a mechanical box, do not drive this vehicle! Deliver it straight to the mechanic.
• Grinding noise when upshifting is most often the result of worn synchronizers. To make sure that the cause is in the synchronizers, use a relaunching technique. When downshifting on any vehicle weighing more than 1000 kg, use a rebase to maintain the synchronizers.
• There are modifications of the automatic transmission, in which the driver himself can choose which gear to engage, but at the same time he does not need to use the clutch. These boxes are electronically controlled. They are often found on German business class vehicles such as the S-Klasse Mercedes. Usually, the position of the gear knob is called M or T, and the gears are shifted by sliding the lever to the right to shift up, and to the left to shift down.
• Semi-automatic transmissions also have a hydraulic clutch. They allow the driver to shift up and down gears himself. Such boxes are often installed on rally cars, and gears are changed by pressing a lever to the right and left of the steering wheel. Often, the right one switches up, the left one down.
• Typical problems with a manual transmission are: grinding noise when shifting, lack of fixation of the engaged gear, too much free play of the shift knob, inability to engage first gear, which is very popular on old German cars, inability to engage reverse gear.
• Automatic transmissions themselves determine the ratio between power and speed, either stepwise or smoothly - such a device is called a variator. The automatic transmission has several positions: Park or Block - the box is locked, the drive wheels are locked, this is equivalent to 1st or reverse gear, with the engine off, Drive - the box automatically changes gears as acceleration, Neutral - the engine is disconnected from the wheels, the wheels can rotate, Reverse - reverse gear, 1 - fixes the 1st gear and 2 - limits the maximum gear of the 2nd. The last two are used to climb a hill to avoid constant gear shifting by the gearbox.
• Clutch faults include incomplete engagement, incomplete disengagement, no engagement, no disengagement, increased force required to press the clutch pedal, and the clutch is lacking too soon or too late.
• The gearbox is designed to convert power into speed, and also to be able to drive the car at different speeds, while keeping the engine speed within acceptable limits. This is the second most complex unit in a car, after the engine.
• You can turn on the first gear with the clutch, switch to the second, and then turn on the first without the clutch.
• The front and rear wheels always rotate at an offset speed. A transfer case is needed to handle this. It works like a differential, just between the front and rear wheels, allowing the engine to rotate them at different speeds.
• The most common propeller shaft problem is vibration on the body. Inexperienced SUV drivers often bend the driveshaft when driving over bumps. A damaged propeller shaft only needs to be replaced - it is useless to repair! Sometimes the "cam joint" may be bent or out of balance. In some cases, repairs instead of replacement can be dispensed with.
• Sometimes the first or reverse gear may not engage, this is normal and is due to the fact that the teeth of the gears rest against each other. To fix this problem, release the clutch while the engine is running and try again. This is normal if it happens from time to time, but if the first and the back do not turn on at all, this is a malfunction.
• Increased rubber wear, loud noise - these are all signs of a faulty dispensing mechanism. The same is true for the gearbox. If the gearbox or the transfer case is out of order - do not use this car!
• The differential very rarely fails. It is possible to detect a malfunction when cornering, driving at a low speed; at high speed, the problem is exacerbated. Do not forget to change the oil in the differential, according to the instructions.
• Manual transmissions have a device that prevents reverse gear while the car is moving forward. Very often, especially on old heavy German cars, this device fails, and it is impossible to turn on the rear one, even in a stationary car. To solve the problem, first engage first gear, then engage reverse.
• A manual transmission is often equipped with a pedal-operated clutch where engine torque is transmitted to the wheels via the drive and driven discs. The driven disc is more subject to wear and is replaceable.
• If a lot of force is required to press the clutch, the springs are too tight on the clutch, or if you have a hydraulic clutch due to hydraulic failure.
• The differential allows the drive wheels to spin at different speeds. This is very important when cornering as the inner wheel travels less distance than the outer wheel.

Warnings

• Never drive a car with a faulty transmission!
• Never try to repair a transmission yourself, unless you are an experienced mechanic who has all the necessary tools and equipment.