In the world oftrucks, the clutch is a crucial component that directly affects the vehicle’s performance and operation. When severe clutch slippage occurs, it can lead to a series of problems that not only disrupt the normal operation of thetruckbut also potentially pose safety hazards. In this article, we will take a deep dive into the issue of severe clutch slippage, focusing specifically ontrucks, using the Sinotruk A7 as an example, and explore its various causes and possible solutions.
Let’s start with understanding what exactly happens when there is severe clutch slippage in a truck. Imagine you’re on the road, and every time you step on the accelerator, the engine revs up, but the truck doesn’t gain speed as it should. This is a clear indication of clutch slippage. It’s like the connection between the engine and the wheels is not as firm as it needs to be, resulting in a loss of power transmission.
Now, let’s take a closer look at the Sinotruk A7, a popular truck model. In the case of this particular truck, one relatively common reason for clutch slippage is related to the pull-type operating structure of the clutch. After a detailed analysis of a user’s vehicle, it was found that when the separation bearing is abnormally damaged, the bearing steel balls or other parts may fall between the cover and the diaphragm spring. This interference disrupts the normal functioning of the clutch, leading to slippage and poor separation. It’s like a small pebble getting stuck in a crucial mechanical joint, preventing it from working smoothly.
In general, the reasons for clutch slippage can be broadly classified into three main categories: issues with the cover assembly, the driven disc assembly, and the matching between the two.
Starting with the cover assembly, one of the key factors is the insufficient working clamping force. Under normal usage conditions, before reaching the specified mileage, if the clamping force attenuation of the cover assembly exceeds the tolerance limit, it can cause problems. This can be attributed to improper operations such as overloading the truck, getting stuck in mud and having to start multiple times in succession. These situations can lead to overheating, burning, or even deformation of the pressure plate, which in turn affects the clamping force. For example, overloading puts excessive stress on the clutch, causing it to work harder than it was designed for. The heat generated from this excessive stress can cause the components to degrade and lose their effectiveness.
Another aspect to consider is the contamination of the pressure plate’s working surface with oil. There are several possible sources of this contamination. Before installation, if the oil on the working surface of the pressure plate is not thoroughly cleaned, it can remain and cause problems later on. Additionally, oil leakage at the rear oil seal of the engine crankshaft or the first shaft of the transmission can also lead to oil getting onto the pressure plate. Similarly, applying excessive lubricating grease at the spline of the first shaft or the bearing sleeve can cause the grease to spread and contaminate the pressure plate. Just like a slippery film on a surface, the oil reduces the friction between the clutch components, making it difficult for the clutch to engage properly and resulting in slippage.
Moving on to the working surface of the pressure plate, foreign matter getting stuck between the cover and the diaphragm spring is another common cause of clutch problems. This can occur in several ways. As mentioned earlier, abnormal damage to the separation bearing can cause bearing parts to fall into this area, leading to slippage, shaking, or poor separation. During installation, if foreign matter in the cover is not properly cleaned out, it can also find its way between the cover and the diaphragm spring and cause similar issues. Improper operation of the clutch, such as burning it out, can cause the friction plate of the driven disc assembly to fall off and get stuck in this area as well. Furthermore, if the dust cover on the flywheel housing is not installed, it leaves the door open for foreign matter to enter and cause problems. These foreign objects act as obstacles, interfering with the smooth movement of the clutch components and affecting their functionality.
The driven disc assembly also has its own set of potential issues that can lead to clutch slippage. Firstly, the friction plate can become contaminated with oil. This can happen due to various reasons, such as oil leakage from the engine or transmission, as mentioned earlier. When the friction plate is contaminated with oil, its friction coefficient is reduced, making it difficult for the clutch to transmit power effectively. Secondly, if the friction plate is worn down to the rivets and not replaced in time, it will lose its grip on the pressure plate, resulting in slippage. This is similar to wearing out the soles of your shoes – once they’re too thin, you lose traction. Finally, a burned or cracked friction plate is also unable to perform its function properly, leading to clutch slippage.
In addition to the individual components, the matching between the cover assembly and the driven disc assembly is also crucial. Using a driven disc assembly from a different manufacturer or an inappropriate specification (including parameters) of either the cover assembly or the driven disc assembly can cause a mismatch. This mismatch can result in improper functioning of the clutch, including slippage. It’s like trying to fit a square peg into a round hole – it just doesn’t work right. Moreover, if the operating system is not fully reset after maintenance or repair, the clutch may remain in a semi-disengaged state, causing slippage. This highlights the importance of proper installation and adjustment procedures.
When dealing with clutch slippage faults, it’s essential to follow a systematic approach for diagnosis and repair. First, check whether the master cylinder, slave cylinder, and pipelines are unobstructed. If there are any blockages, they need to be adjusted first. However, if the fault persists after adjustment, it’s necessary to disassemble and inspect the clutch. During this process, special attention should be paid to the gap between the push rod of the transmission cylinder and the piston. When adjusting, gently push the pedal by hand to feel the push rod pushing against the piston. Then, adjust the height of the limit bolt so that the gap between the limit bolt and the clutch pedal is approximately 0.5mm. After that, tighten the nut at the limit bracket to ensure that there is a gap of 0.5mm – 1mm between the push rod and the piston. It’s important to note that this gap should not exceed 1mm, as doing so would reduce the effective stroke of the transmission cylinder, which can further affect the clutch’s performance.
Clutch slippage is not limited to heavy trucks like the Sinotruk A7. It can also occur in some light truck-mounted cranes, wreckers, oil tankers, and other vehicles with similar clutch systems. Therefore, regardless of the type of vehicle, it’s crucial for drivers and maintenance personnel to be aware of these potential issues and pay attention to regular maintenance and inspection. By doing so, they can detect and address problems early on, ensuring the safe and efficient operation of the vehicle.
In conclusion, severe clutch slippage in trucks is a complex issue with multiple potential causes. Understanding these causes and taking appropriate preventive and corrective measures is essential for maintaining the performance and reliability of the vehicle. Whether it’s proper installation, regular maintenance, or careful operation, every aspect plays a vital role in ensuring the smooth functioning of the clutch and the overall safety of the truck on the road.
