Car owners become interested in the issue of gear ratios in two cases. The first one is for reference and characterizes the inquisitive. After all, the more you know about the structure of the car, the longer and more competently it will work. However, most often the gear ratio is determined in case of problems with the gearbox.
Knowing what gear ratio your car has, you can:
- Always correctly replace a faulty gearbox or its parts;
- understand how the car will behave when installing a gearbox with parameters different from the original factory ones.
Definition of the concept
What is the gear ratio? Any gearbox is used to transmit torque from the gearbox to the wheels. In this case, the rotation speed always decreases. The gear ratio is precisely an indicator of how many times this reduction occurs. For example, the number 5.125, found in Gazelle gearboxes, shows that the rotation speed from the input shaft to the wheels is reduced by 5.125 times.
In practice, the gearbox in a car is located on the drive axle. If we are talking about all-wheel drive options, there are two gearboxes, one for each axle. Domestic cars produced by VAZ and GAZ have a rear gearbox, with some exceptions. To determine the gear ratio, you can do this in several ways:
- theoretical;
- practical;
- calculated
Where are the gear ratios written?
The easiest way to find out the gear ratio of the rear axle of a car is to look in the documentation. For many foreign cars this number is encrypted in the Vin number. For domestic cars, there are standard gearboxes for certain models. At the same time, there are cars that can be equipped with a number of gearboxes with different gear ratios.
It is possible to find out information specifically and in detail. There is no need to remove the gearbox for this. If there is information, it is located in a place convenient for inspection.
Breakdowns, their diagnosis and possible repairs
A large amount of various iron in the Niva transmission can cause a lot of anxiety to the owner of the car with enviable regularity. Even problems that are obvious at first glance may not always be caused by a specific defect. Accordingly, you also need to carefully diagnose and “treat” the car so as not to return to the same problem several times.
It is easy to check the operation of the gearbox. Even if there is no lift, accelerate the car, put it in neutral and roll until it comes to a complete stop. This is where the slightest weak point will show itself, regardless of what gearbox is on the Niva. It happens, by the way, that noise from the transmission makes itself felt even through the running engine. Let's try to figure out what to do.
Hear a continuous hum when the car is moving
Congratulations! There is a high probability that you bent the rear axle beam in the next “rides”. The bent drive rods found on the VAZ 21213 can also provoke extraneous noise in the stern area when moving. Broken bearings and “tired” gears of the gearbox or partially “licked” splines also greatly increase the noise level.
Finally, it would be a good idea to check the oil - this is the simplest and often the most effective method of getting rid of the problem. A noticeable sign of oil starvation of the steel elements of the gearbox will be abundant oil leaks.
Something makes noise when accelerating and braking the car
It wouldn’t hurt to check the clearances of the drive gear shaft with the flange, the final drive gears themselves, and the condition of the bearings. In general, you need to clearly catch the moment - when exactly extraneous sounds are heard and their peculiarity - clanging, grinding, beating, etc. This will allow you to more accurately determine what exactly needs to be repaired, adjusted or replaced on the Niva 21213 1997.
Oil. Oil again
With the oil supply to steel friction pairs, everything seems to be simple and clear. When there is enough lubrication, components and assemblies work fully even in extreme conditions. No oil means critical wear of parts and, as a result, expensive repairs.
Oil leaks can be detected by visual inspection. Lubricant may leak due to damage or natural wear of the drive gear oil seal. A leaking axle seal will show traces of oil on the brake drums and pads. Finally, loose bolts of the rear axle housing (housing) or leaky sealing gaskets are also quite easy to see and, accordingly, replaced, and the bolts tightened.
It is better to fill in synthetic oils, and if you have any tricky cross-wheel self-block installed, then in strict accordance with the recommendations of the differential manufacturers. Typically these are any oils labeled LSD.
Practical way to determine
The most accurate way to determine the gear ratio is to count the number of teeth on the drive and driven gears. Then the larger number is divided by the smaller number, which gives the desired result. For example, in the domestic model VAZ-2106, the number of teeth on the drive shaft is 41, and the number of teeth on the differential driven gear is 11. As a result, dividing one number by another, we get: 41: 11 = 3.9.
This method of determination is the most accurate, but at the same time not at all practical. Because for this option it is necessary to disassemble the gearbox and get the necessary parts. And this is not only inconvenient, it is always expensive.
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Calculation method
Is it possible to find out the gear ratio of an unknown car without disassembling the gearbox? It turns out there is such a way. To do this, the axis on which the gearbox is installed is hung on supports. The position of the drive shaft and wheels is remembered. It is convenient to do this with simple marks. Then the wheels are turned until the marks coincide again, counting the number of revolutions of the wheels and shaft separately. It is more convenient to carry out this procedure with an assistant.
After obtaining experimental data, the number should be calculated by dividing the number of shaft revolutions by the number of wheel revolutions. The accuracy of this method is approximate and is improved only by being careful when counting and combining marks.
Main pair of gearbox 3.94 (71/18) VAZ 2112 /new model/
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We install a gearbox with a different gear ratio
What happens if the gearbox being replaced has different parameters from the installed ones? For example, consider the gear ratios of VAZ gearboxes. The line of units is represented by four gearboxes. Their numbers fall in the range from 3.9 to 4.44.
A gearbox with a number of 3.9 will be the fastest of the family, and a gearbox with a number of 4.44 will be the most high-torque. Because in the first case, the power transmitted by the input shaft decreases only 3.9 times versus 4.44. It turns out that if the gearbox transmits torque faster, the car becomes more “nimble”. If you replace the gearbox with a version with a lower gear ratio, the car accelerates more slowly, but becomes more passable and high-torque.
When installing a gearbox with a number different from the factory number, it is imperative to check the speedometer readings. Most often he starts to lie. The problem can be solved by adjustment, and sometimes you have to change the speedometer cable. The most difficult thing when replacing a gearbox is not the removal and installation, as it might seem initially, but the adjustment and configuration. Without proper adjustment, even a properly selected gearbox can become unusable after several thousand miles.
Oil
It is worth noting that the VAZ-2107 gearbox, or rather its operating principle, is based on the meshing of gears. Accordingly, with constant rotation there will be significant production. To increase the service life, special oil is poured inside the gearbox. It forms a thin film behind the teeth. On the “seven” you can use thick gear oil. It is perfect not only for the gearbox, but also for the rear axle. We also note that the lubricant has a certain service life. Experts recommend changing this fluid at least once every thirty thousand kilometers.
Gear ratios of VAZ gearboxes
Let's take a closer look at the rear gearboxes installed on domestic VAZ cars. As mentioned earlier, there are a total of four gearboxes that were equipped with rear-wheel drive versions of AvtoVAZ. The fastest gearbox belongs to the sixth model of the Zhiguli. The rear axle gearbox of the VAZ-2106 has a gear ratio of 3.9. This figure is obtained from the ratio of the teeth of the input shaft and driven gear of 43:11.
The next fastest gearbox with a number of 4.1 belongs to the VAZ-2103. This unit has average, but also the most balanced indicators, such as acceleration, maximum speed and power. The first VAZ models had the highest torque gearboxes. Thus, the VAZ-2101 had a power transmission device according to the scheme 43: 10 = 4.3, and the VAZ-2102 - 40: 9 = 4.44. Because of this, the second model was the most convenient for driving with a trailer, although it had the lowest maximum speed - 145 km/h.
What gear ratio of the VAZ rear axle gearbox can be considered optimal? Each Zhiguli car owner will decide the answer to this simple question himself. To do this, it is enough to understand for what purposes the car will be used. If this is primarily a workhorse, the best option would be the most powerful gearbox with a 4.3 number. Ideally, of course, to install the “double” option, but the main pairs with the number 4.44 stopped being produced with the cessation of production of the VAZ-2102 a long time ago. For ordinary driving in urban conditions, the best gearbox is from a VAZ-2106 with a number of 3.9.
A few words about the gear ratio of all-wheel drive VAZ-2121 gearboxes. Since there are two gearboxes on such cars, it is important that the number is the same and corresponds to the ratio 41: 10 = 4.1.
Teeth Features
Just like a gearbox, it uses a pair of gears. The VAZ-2107 steering gear is no exception. On the “seven”, the driven and driving gears are located at an angle (that is, not straight, but helical). The main feature of the pair is less load on the teeth, smooth and quiet operation. The rear axle of the “six” and other classic VAZ models is designed using the same principle.
- Cylindrical.
- Conical.
- Worm-shaped.
If we talk about the VAZ-2107 steering gear, then the operating principle here is based on a worm pair. As for the gearboxes themselves, they also include a hypoid gear. Here the gears, unlike bevel gears, do not lie in the same plane.
