Malfunctions of the transmission: why did the gear start to fly out?
The manual transmission is considered a model of reliability compared to the various types of automatic transmissions, in which the choice of gear is controlled by the electronic brain. But there are blemishes in the sun, too. Let’s talk about one fairly common defect: gear knockout.
Determining the defect is so simple that it does not cause difficulties even for beginners. If a person knows how to drive a car with a manual transmission, he will understand at once, that he switched on the gear, started to move, but all of a sudden there were problems. Acceleration was lost, the speed dropped, and the gearbox control lever itself was in neutral position. Reengaging the same gear again had the same result. The only way to continue driving in that gear is to forcibly hold the shift lever in the right position.
Most of the time, in order to drive to the place of repair, you can simply not use this gear. With modern multi-gear boxes, the gap between gears is not very big, which allows you to freely do without one gear. The wide dynamic range of the modern injection engine allows using the crankshaft rotation speed from 1200 to 5500 rpm. It is possible to drive to the garage, but the defect should be eliminated.
Causes of gear dislocation
Wear of the powertrain mounts. The power unit swings much harder than it should, and instead of the driver engaging and disengaging gears, the bouncing gearbox does it by itself. More often such defect is reacted by gearboxes with drive of controlling with hard pull rods.
Gearbox control with a pull rod. The second link is reactive, but its ability to reduce parasitic oscillation has proven to be poor.
Gearbox control with a pull rod. The second link is reactive, but its ability to reduce parasitic oscillation has proven to be poor.
If the box has cable control, it is much more indifferent to the destroyed powertrain supports. “Soft” cables are capable of damping all engine fidgeting.
This defect sometimes knocks out paired gears, such as second and fourth, because the direction of engagement (and disengagement) of these gears coincides. Although it is not always the case: some gears are worn more – others less, and, accordingly, the possibility to hold the gear engaged is different. Plus the dynamic jerking in the second gear, for example, is much stronger, than in the fourth.
The treatment is simple. It is necessary to replace power unit supports – and faster, because not only gearbox suffers. The pipes, hoses, cables, harnesses of wires, which connect a power unit with other units of a car, are bent and can break from excessive mobility of the unit, and believe me, there are a lot of them.
Renault Duster at the moment of engine extraction. Pay attention to the number of “umbilicals” with which it was connected to the car!
Renault Duster at the moment of engine extraction. Pay attention to the number of “umbilicals” with which it was connected to the car!
Worn actuator mechanism. A severely misaligned or worn actuator will not fully engage the gear. If it is not fully engaged, it will kick out at the first opportunity. The gear is more prone to kick out when driving without load (coasting): when the engine turns the wheels, the meshing of the clutch teeth is much “stronger” than when braking the engine. Or as people say: “Try to pull the gear under gas or under a gas release – and you’ll understand everything”.
The condition of the hinges that connect the box levers to the cables directly affects gear engagement (and disengagement).
The condition of the hinges that connect the box levers to the cables directly affects gear engagement (and disengagement).
Clutch. The clutch, on the other hand, can have almost no effect on gear knock-out. But if the clutch squeeze is insufficient, it makes it difficult to fully engage the gear. However, this defect can not be called a knock out gear.
Internal gearbox defects
The cause of tooth wear on the clutches can be a malfunction in the clutch mechanism or its drive, when there is no separation between the engine flywheel and the transmission’s primary shaft. Naturally, this knocks out the gear, the details of which are damaged teeth. The most frequently the gear is dislodged in such situation at sudden acceleration on this gear or at intensive engine braking.
What to do, if the gear is knocked out of gearbox
Those who are far from car themes associate the concept of gearshift with a long-awaited rest or seeing off your nearest and dearest to the airport. An experienced driver feels discomfort when the gearbox flies out. After all, it is an obstacle for driving at a certain speed.
Let’s look at the main causes of gearshift out on all types of gearboxes that automakers offer.
Manual transmission.
The gear units are on the secondary shaft. In a normal manual transmission, when one of the gears is engaged, the hub and clutch of the corresponding gear block are driven, which sends a command through the chain to take a certain action. The movement occurs toward the loose pinion, which transmits the momentum to the vehicle’s drive.
Among the causes that cause the departure of a particular or all gears are:
- Wear of the locking ring of the synchronizer. In this case, only one gear is knocked out – for example, first or reverse.
- Physical wear of the disengaging fork. Then the speeds may not shift, leaving only neutral possible.
- Failure of the pinion responsible for a particular gear.
The advantage of a manual transmission is the ease of maintenance. Any of these malfunctions are easy to fix without outside help.
Automatic transmission
Here it is more appropriate to call it not a slip, but a slip. A sudden change from 3rd or 4th gear to neutral leads to a noticeable deceleration of the vehicle. Or vice versa, to acceleration. Everything depends on its function – lowering or raising. It creates inconvenience for the driver and danger of hitting the front or rear.
The signal to errors of automatic transmission also becomes the car’s brooding. If it hesitates when switching from parking mode to driving and vice versa – it is better to be engaged in service of the unit at once.
To the counterparts of the mechanical parts – exhaustion of the life of forks and couplings, another is added – electronics. A short circuit, internal rubbing of parts, mechanical damage of the chip and a number of other factors can lead to an error. Due to the presence of the electronic unit, repair of the box is only possible at the service station. Add call of a tow truck to the diagnostics and spare parts replacement costs – towing a car with automatic transmission is undesirable.
Variator
There are no physical gears in the variator. It is programmed to transfer torque as comfortably as possible with reduced fuel consumption. Although it is not able to kick out a gear, it is still prone to breakdowns.
The driver has to constantly listen to what’s going on inside the variator box. The constant friction of the variator units against each other leads to grinding and the formation of metal dust and shavings inside. Filters are available to trap that dust, but they don’t provide a complete guarantee of cleanliness. Over time, settled dust causes oil pump pressure spikes and drive belt failure.
The most innocuous situation is when the variator radiator is clogged. Its location collects all the dirt inside with the incoming air flow. This is what interferes with the proper functioning of the variator. For preventive purposes, wash all radiators of your car at least once every six months.
Robotic Transmission
Maintenance of this kind of gearbox is trusted to experienced auto craftsmen. The loss of gears on a robot is associated with both electrical causes – for example, leakage of transmission fluid and shorting of the corresponding circuit, as well as with the wear and tear of parts.
Also driving on one of the speeds may be impossible due to burnout of the contact group of the ECU and the specific gear. But often the cause of deterioration of work becomes trivial debris, delivered from the clutch mechanism. Do not be lazy to remove it at every opportunity, and then the robot box will say thank you.
Completion
We’ve only cited the most common breakdowns and out of speeds on different types of gearboxes. But there are also minor nuances that lead to gearbox flyouts. And in the near future, AUTOSOWS will break down the mechanism into molecules in detail. Stay tuned for updates!
