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Riding with an automatic transmission is so convenient that many are willing to overpay 40, 000-80, 000 rubles for this. Even despite the fact that, for example, a hydromechanical unit in urban conditions can increase fuel consumption by 10-15%. But designers are not sitting idle: the family of automatically controlled boxes is growing. There are also those with which the fuel economy of the car does not deteriorate at all. Among them is the DSG (Direktschaltgetriebe) gearbox of the German Volkswagen concern.
Fans of twisting eights on the pavement happen to pay for a new differential case
Fans of twisting eights on the pavement happen to pay for a new differential case. Fans of twisting eights on the pavement happen to pay for a new differential case.
IDEOLOGY EXCELLENT. FROM OTHERS
To the connoisseur of mechanical transmissions, the DSG design does not seem too sophisticated, we explain its scheme. It is based on a pair of familiar manual gearboxes KP1 and KP2, but with an unusual organization of work. The input shaft of each is driven by its own clutch - SC1 and SC2. When, for example, the SC1 clutch is operating and one of the gears it serves (first, third, fifth or seventh) is engaged, the SC2 clutch with its gears (second, fourth, sixth and R - reverse) rests in anticipation of its turn. As the car accelerates (or, conversely, decreases in speed), the torque is transferred to the wheels alternately through one gearbox and then through another. Of course, both the clutches are idle off the engine. And the Mechatronic electro-hydraulic brain, which takes into account a number of parameters of the machine’s operation, monitors the peaceful interaction and the clear work of all mechanisms. He himself decides at what pace it is necessary to switch from one transmission to another, and also up or down. Only the reverse includes the driver himself.
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Imagine how DSG works, for example, at the time of transition from third gear to fourth. While the torque is transmitted to the wheels in third gear, the fourth gear is already engaged, but its clutch is open at this time. Having made the decision to change gear, Mechatronic disengages the first clutch according to a certain algorithm and simultaneously engages the second. As the torque falls from the third gear, the wheels begin to receive the necessary torque from the fourth. As a result, there should not be any failure between the gears, there should be no jerk, only the traction force of the wheels will softly decrease and, naturally, the acceleration of the machine will decrease. In addition, a shift indicator will be reported by the mode indicator in the instrument cluster. If the control unit is correctly configured and both clutches are serviceable, then the time of the transition described by us from one gear to another is measured in milliseconds - a professional racer will not be able to compete with DSG in the switching speed.
Of course, the real mechanics of the DSG are much more interesting than the usual gearbox. So, both input shafts, as well as clutch discs, are made according to the coaxial scheme. There are already three secondary shafts - due to the tight layout of the unit and taking into account the reverse gear. The design is not at all flat, as in the diagram, - the secondary shafts of the KP1 and KP2 parts, as well as the reverse gear, are compactly (in accordance with the available places) attached to the coaxial primary ones. Naturally, the nodes look quite complex.
Even the large teeth of the driven gear of the main gear cannot withstand the aggressive driving style
Even the large teeth of the driven gear of the main gear cannot withstand the aggressive driving style. Even the large teeth of the driven gear of the main gear cannot withstand the aggressive driving style.
The DSG has undeniable advantages over conventional mechanics. Congenital sores of the latter have long been known: even with the most skillful gear shifting, the flow of power transmitted from the engine to the drive wheels is interrupted, even for a short time. And since the clarity of the gear shift also depends on the serviceability of the gearbox mechanisms, for a novice driver in difficult situations this failure can be delayed, which is unsafe.
The DSG also wins against hydromechanics with its slippage, since it always transfers full torque to the drive wheels, moreover, it does this continuously, which contributes to fuel economy.
Each release bearing has its own fork, - changing the clutch, put a new fork along with the bearing
Each release bearing has its own fork, - changing the clutch, put a new fork along with the bearing. Each release bearing has its own fork, - changing the clutch, put a new fork along with the bearing.
ANNOUNCE - GO
The lubrication system is separate: 1.7 liters of gear oil are poured into the crankcase with shafts and gears, and about 1 liter is placed in the hydraulic unit. These oils are incompatible. The manufacturer does not provide for their replacement: in the crankcase of the gearbox there is no filling (control) plug at all. However, service and repair specialists still recommend replacing the oil every 50, 000 km. But in this case, in order to guarantee the correct level, you will have to merge the old one, and pour the new one in compliance with a certain procedure. Do not do this with the garage master: a mistake is fraught with premature wear of parts or breakage.
The dual-disc clutch is massive and bulky. In the foreground - large teeth for communication with the engine flywheel. The kit includes a pair of release bearings with forks and a set of shims
The dual-disc clutch is massive and bulky. In the foreground - large teeth for communication with the engine flywheel. The kit includes a pair of release bearings with forks and a set of shims. The dual-disc clutch is massive and bulky. In the foreground - large teeth for communication with the engine flywheel. The kit includes a pair of release bearings with forks and a set of shims.
CHECK THE THEORY OF DIAGNOSTICS
Alas, even for a lover of measured, calm driving with a DSG, the theory is not always fully confirmed by practice. So, sometimes the owners complain of jerks and tremors when starting off, and on the rises, the car can roll back a little. If you contact a specialist in diagnostics, he may reassure you with the following information: in the operation of today's DSG, specific modes with small jerks and twitches are possible, these modes are even considered normal. It is possible that one day a new design will be born, spared from such shortcomings.
Diagnosis itself is quite traditional. The client cries to the master in a vest, followed by a test drive. Next, the specialist connects the scanner, analyzes the information received and decides what to do. Minor flaws are often eliminated by elementary adjustments and (or) adaptation of the control unit. If this does not help, you will have to remove the DSG from the car for repair. In some cases, all nodes and mechanisms are subject to revision. But the main attention is paid to the valve body and clutch. The first can lead an unprepared person to awe. At first, faulty valve bodies were simply replaced with new ones, making it easier for the owner’s wallet by 70, 000–80, 000 rubles. Now they are already being repaired. A reconditioned unit is at least half the price of a new one. Only instances with irreparable mechanical damage, such as those resulting from an accident, cannot be repaired.
The secondary shaft roller bearings sometimes fail even at low mileage, regardless of driving style and vehicle operating conditions
The secondary shaft roller bearings sometimes fail even at low mileage, regardless of driving style and vehicle operating conditions. The secondary shaft roller bearings sometimes fail even at low mileage, regardless of driving style and vehicle operating conditions.
Even Edison’s descendants are not advised to replace the unit on their own, because a new one should definitely check whether the software version matches the machine’s configuration and, if necessary, adapt. Here you can not do without diagnostic equipment. If this is ignored, the performance of the box may deteriorate or the car will not budge at all.
The dual clutch DSG is a serious and moody knot. Some samples can withstand 100, 000 km until the first slippage symptoms, while others can hardly live up to 40 thousand. When repairing a DSG, it is advisable to change the entire clutch assembly. Today, the price of the issue is forty to fifty thousand. There are several reasons for the DSG failure after a short mileage - from an overly aggressive driving style to inconsistent clutch operation due to failures of the valve body or incorrectly adjusted clearances. The latter deserve special attention. The necessary adjusting washers are in each new clutch set, and, of course, the corresponding measuring tool will be required. If you just put in a new kit, without worrying about the gaps, the shocks and jerks in the system may be stronger than before the replacement.
Plastic lining on the shift forks wear out faster during intense acceleration and braking
Plastic lining on the shift forks wear out faster during intense acceleration and braking. Plastic lining on the shift forks wear out faster during intense acceleration and braking.
The concern is constantly improving the clutch design. Surveys of owners and specialists show that the last, fourth option has become noticeably more reliable.
WHAT IS NOT ETERNAL UNDER THE MOON?
Worked DSG boxes are often disturbed by traffic noise. If it seems like a kettle is boiling in a box, then most likely the roller bearings of the secondary shafts are guilty of this. It seems that they are overloaded by contact voltages, they sometimes crumble, without having passed even fifty thousand. And this is even with the driver who regularly performed maintenance! Often the teeth of the gears break down, after which a knock is heard when a broken tooth comes in contact with a pair of teeth of another gear. What can we say about lovers of "sports" driving, crumbling even the teeth of the differential gears!
A broken gear is the result of not only the accumulated fatigue of the material, but also the next frisky start from a traffic light. But how many victories the owner provided
A broken gear is the result of not only the accumulated fatigue of the material, but also the next frisky start from a traffic light. But how many victories the owner provided! A broken gear is the result of not only the accumulated fatigue of the material, but also the next frisky start from a traffic light. But how many victories the owner provided!
At the same time, the two-stream torque transmission scheme described by us increases the survivability of the machine, allowing it to reach the repair site on its own with some breakdowns. For example, if something broke in the third gear, the entire KP1 row will turn off - from the first to the seventh, but in even KP2 gears the car will move, albeit not as smoothly as before the breakdown. At the same time, the reverse gear will remain, and in the instrument cluster the gear change indicator will blink.
But if the electric pump of the control unit breaks or its electric circuit fails, movement is impossible. This happens, for example, after prolonged parking of the car: since the soured pump scrolls tight, when it is turned on, the load in the electrical circuit can increase so much that the control bus in the circuit board will burn out. True, now this is no longer a reason to change the unit - unofficials undertake such repairs.
Electro-hydraulic control unit "Mechatronic". The view is impressive, but they have already learned to repair them
Electro-hydraulic control unit "Mechatronic". The view is impressive, but they have already learned to repair them. Electro-hydraulic control unit "Mechatronic". The view is impressive, but they have already learned to repair them.
To increase the demand for cars with DSG boxes, Volkswagen extended the warranty for this unit to five years. True, it applies only to the Mechatronic unit, and damage to the mechanical part - shafts, gears, bearings, etc. - is not referred to as warranty.
The immediate future of the concern in the field of automatic gearbox development is connected with this device. For example, in the new “Octavia” you will not find a hydromechanical machine in any configuration - only DSG!
