What is a car gearbox, what are its structure and function, how to determine a malfunction and why the oil in the gearbox needs to be changed as regularly as changing the oil in the engine and changing the oil in the automatic transmission - we will answer these questions in this article and help you do right choice.
A gearbox is a mechanism as part of a car drive that transmits and converts torque received from the engine crankshaft. The torque is reduced (reduced, hence the name) and transmitted further to the transmission units. The gearbox device is a bevel gear located inside a separate housing.
Depending on the location, the gearbox of the front and rear axles is distinguished. For front-wheel drive cars, it is combined with the gearbox and installed, respectively, at the front. For rear-wheel drive vehicles, it is installed on the rear axle. All-wheel drive vehicles are equipped with two gearboxes connected to each other by a driveshaft.
The main reasons for changing gear oil
The frictional force that is present when the parts of the gear assembly are in constant contact leads to a chain reaction. At the output of a gearbox without lubrication, the gearbox itself, the special equipment it powers, and the technological process with its participation may suffer.
- During operation of the gearmotor, heat is generated. The gearbox lubricant heats up and loses its positive properties (lower viscosity means higher friction force).
- Abrasion of assembly parts leads to the entry of small hard chips into the lubricant, which also reduces their ability to compensate for frictional force.
- Deterioration of the oil in the gearbox provokes early wear of its parts and failure of entire components.
- If the gearbox breaks down during the active stage of operation, the equipment can also suffer a serious malfunction.
The specific timing of filling oil into the gearbox depends on the type of worm gear motor and its operating schedule. Do not forget that due to the same heat, the amount of lubricant decreases naturally.
In this matter, experts recommend relying on the recommendations of the mechanism manufacturer, which are detailed in the instructions for use. You should also focus on them when choosing consumables.
When to change
The replacement frequency is on average 50 thousand kilometers for cars with a manual transmission, and 30 thousand for an automatic one.
It is more often necessary to change the oil on cars that are used in difficult conditions, which include:
In a new car, it is recommended to replace it after the first 2-3 thousand mileage. The fact is that at the initial stage of work, new components undergo the so-called “grinding in”, which is characterized by increased formation of wear products.
Many car owners change the oil in the gearbox at the same time as the manual transmission, since both units use transmission fluid.
Be sure to check the level and condition of the oil in the gearboxes after purchasing a car on the secondary market. Usually, before selling, owners change lubricants only in places where they can be easily checked. Gearboxes are not one of these.
Performance Features
Scientists at the API Institute, operating in the United States, have created a classification that provides a comprehensive assessment of gearbox oils depending on their performance properties. Now it is distributed all over the world. The system provides five categories that indicate the level of quality and application features of products with the corresponding index. In the domestic GOST, the classification is indicated only in the letter designations placed at the beginning of the index.
Recommendations for choosing oils for the KamAZ axle
How much oil to pour into the gearbox
— The front axle gearbox holds 5.3 liters of transmission oil. — 7.75 liters of oil are poured into the middle axle gearbox. It is advisable to fill through 0.75 liters, the remaining 7 liters into the gearbox. — 7 liters of oil are poured into the rear axle gearbox of KamAZ 5320-2402010-10.
There are many types of bridges with a similar structure, but there are exceptions. Therefore, when filling oil, be guided by the level of the control holes.
Selecting oil for KamAZ gearbox
The choice of oil depends on the preferences of the driver/mechanic and his financial capabilities. It is better to choose gear oil from well-known manufacturers 75W-90 (for temperate climates), 80w-90 (for warm climates), 85W-90 (for hot countries).
— The most inexpensive: TAD-17
and (analogous to TM-5-18) - universal all-season mineral oil for truck transmissions. It has a particularly strong oil film, ensuring reliable operation of the transmission under intense friction conditions in the contact zones, and is operational in the temperature range from -25°C to 130-140°C. In the cold season at temperatures of -30..-35 degrees, the oil thickens greatly!
— Castrol Syntrax Long Life 75W-90
— Fully synthetic universal final drive oil. Particularly recommended for final drives of heavy commercial vehicles. Approved by MAN, Scania and ZF.
— Shell Spirax S6 AXME 75W-90
— unique synthetic oils for drive axles and gearboxes. It has energy-saving properties, as well as the ability to extend replacement intervals, approved by the manufacturers: Volvo, MAN, Meritor, Scania, DAF, Mack, Iveco, ZF.
— MOTUL Motylgear 75W-90
— transmission oil for heavily loaded gearboxes and hypoid axles without automatic locking and limited slip systems. Standards: API GL4 and GL5; MIL-L-2105D.
— Mobilube HD 80W-90
is a high-performance oil for heavily loaded transmissions, developed from high-performance base oils and an advanced additive package. Designed for final drives where extreme pressures and shock loads are expected.
— Esso Gear Oil GX 75W-90
— partially synthetic all-season transmission oils for use in heavily loaded modern final drives (gearboxes).
Checking the oil level in the crankcases of the main gears of the drive axles
To check the oil level, place the car on a horizontal platform and 5-10 minutes after stopping the engine, check the oil level by unscrewing the inspection hole plug on the axle housing. If there is no oil leakage from the inspection hole, add oil to the lower edge of the inspection hole through filler hole.
The attractive qualities of mineral water and why semi-synthetics are better than others
The main advantage of mineral oil is its affordable cost. Due to the fact that it contains virtually no additives, the most attractive price for the end user is achieved.
In addition, the mineral oil poured into the bridge has sufficient viscosity so as not to penetrate the seals. The change in viscosity indicators with sudden temperature changes is insignificant.
The golden mean is semi-synthetics. It is not as expensive as fully synthetic axle oil, but at the same time it protects moving parts of the units more effectively than mineral oil.
It is important to change the oil on time, since without it metal shavings will accumulate inside. Ultimately, this may cause the mechanism to jam.
The video demonstrates the characteristics of domestic axle oil TAD-17:
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29.11.2017
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Classification
According to DIN
According to DIN 51517, the classification and marking of gear oils is as follows.
Class
Description
Properties
Mineral oil without additives
The most affordable product. Compatible with unloaded and lightly loaded systems
Mineral oil with anti-corrosion and antioxidant additives
Oils with extended shelf life for systems without anti-wear requirements
Mineral oil with additional anti-wear additives
Used in mechanisms that require enhanced protection against wear of parts
According to AGMA
Another generally accepted classification was developed by the American Lubricants Manufacturers Association (AGMA). This specification determines the viscosity of oils for gears and gearboxes. The viscosity ratio according to AGMA and ISO standards is given in the table below.
AGMA
Corresponding ISO grade
AGMA (EP gear oils)
AGMA (synthetic gear oils)
According to ISO (gear oil viscosity grades)
The viscosity of gear oils is assessed according to the ISO VG standard. The abbreviation VG stands for viscosity grade, which translated from English means “viscosity grade”. High-quality gear oils meet the requirements of ISO classes from 2 to 1500. ROLF Lubricants GmbH products are presented in the following viscosity range: 68, 100, 150, 220, 320, 460.
Bearings and lip seal
| Standard size | Stub | Lip seal. Input shaft. 1 PC. | Lip seal. Output shaft. 2 pcs. | Bearing. Input, shaft, motor flange. 1 PC. | Bearing. Input shaft, rear lid. 1 PC. | Bearing. Output shaft 2 pcs. |
| 030 | 032×7 | 20x30x7 | 25x47x7 | 61904 | 6201 | 16005 |
| 040 | 040×7 | 25x35x7 | 30x40x7 | 6203 | 6005 | 6006 |
| 050 | 047×7 | 30x47x7 | 40x62x7 | 6204 | 6006 | 6008 |
| 063 | 052×7 | 35x52x7 | 45x65x8 | 6205 | 6007 | 6009 |
| 075 | 062×7 | 40x60x10 | 52x72x8 | 32008* 6008 | 30206* 6206 | 6010 |
| 090 | 062×7 | 40x60x10 | 65x85x10 | 32008* 6008 | 30206* 6206 | 6012 |
| BY | 072×7 | 50x68x10 | 65x85x8 | 32010* 6010 | 32207* 6207 | 6013 |
| 130 | 072×7 | 50x68x10 | 70x90x10 | 32010* 6010 | 32207* 6207 | 6014 |
| 150 | 085×10 | 65x90x10 | 90x120x10 | 6013 | 6209 | 6018 |
*Tapered roller or radial ball bearings can be installed on the high-speed shaft (optional)
The opinion of experienced people about changing the oil in the gearbox
- Does the manufacturer recommend changing it every 100 thousand? Repair professionals recommend every 80 thousand.
“I changed the oil in the rear axle gearbox at a car service after 100,000 km, as recommended by the car manufacturer. However, specialists at the service station advised doing this every 80,000 km. I trust these guys, they never let me down. I don’t recommend changing the lubricant in private auto repair shops, because no one can guarantee that such a mechanic knows how much fluid to fill.”
Do you need to change the oil in the gearbox? Stop by the pharmacy first
“I drove 83,000 km, drove the car for 6 years. When the time came, I changed the oil in the rear gearbox with my own hands. In total, approximately 550 ml of lubricant was required. I filled it from a four-liter canister, so I can’t say the exact volume.
The replacement was carried out on a summer cottage; there was no overpass or lift. I placed the car on stands (17 cm high). Filling with lubricant is the simplest procedure, the cost of changing the oil in the gearbox is minimal, because the cost of lubricant is low. And you don’t need to pay for the work, because I did everything myself.
Don't know how to add liquid? Take Janet's syringe. We put a flexible nozzle on it, about 20 cm long. The syringe contains 160 ml, I filled about three and a half syringes.”
For three-liter models, the transfer case is in a different place
“If the car has a 3-liter engine, then the transfer case will be located next to the right front wheel. In this case, it will not be easy to get to the filler bolt. The automaker made an o on the head of the filler bolt to make it easier to navigate when replacing. I carried out the replacement after first studying the book from the publishing house “Third Rome”; if desired, you can download it, since it is freely available.”
We recommend
“A friend has a VAZ 4, no one has ever changed the lubricant in the gearbox, but there was no buzzing in the bridge. When I decided to change the old fluid, it was thick, like grease. After the replacement, he drove 2,000 km, and the gearbox began to hum. At the car service center, the guys said that in such cases, when no one has ever filled in new lubricant, the replacement should be carried out in several stages: first, drain a quarter, add new lubricant. And how he did it: he removed all the dirt that had gotten into every crack and crevice with new oil. And all the holes were exposed again.”
Don’t change the oil in the gearbox when it’s cold
“How to perform the replacement: loosen the drain nut, tighten it. Then you need to drive the car for 10–15 km, after which remove the lubricant. The heated liquid will drain faster. After that, inspect the filler plug. It needs to be checked in advance; perhaps it is stuck and unscrewing it will be problematic.”
Checking the oil level
Control checks of the fluid volume in the gearbox should be carried out every 10 thousand kilometers, as well as when malfunctions or visual leaks occur. Checking the oil level in the rear axle is quite simple. To do this, you will need a container with a volume of about one and a half liters, a 17mm wrench and a screwdriver. The next steps are:
- the car is placed on a viewing hole, overpass or lift;
- the filler plug is cleaned of dirt;
- use a 17 key to unscrew the filler plug;
- The oil level is controlled with a screwdriver: the liquid should reach the edge of the hole.
If there is insufficient protective liquid, it is necessary to add it using a syringe or other device.
