Why Nissan CVTs FAIL
TLDRThe video script offers an in-depth exploration of the continuously variable transmission (CVT), focusing on its inner workings and common failure points, particularly in Nissan vehicles. The host begins by examining the CVT's compact design, including the torque converter, pulleys, and belt system, which allows for smooth gear ratio adjustments. The disassembly process reveals the transmission's hydraulic and electronic control systems, highlighting the fewer number of clutches and solenoids compared to traditional automatics. The star of the CVT is the steel belt, composed of small steel pieces for flexibility and strength. However, the script also discusses the belt's vulnerability due to high torque loads in powerful vehicles, wear and tear, and inadequate cooling systems leading to premature failure. Despite these issues, CVTs are praised for their smooth power delivery and better fuel economy, which is why they are favored in economy cars. The host advises CVT owners to perform regular maintenance and avoid aggressive driving to extend the transmission's life. The script concludes by emphasizing the high cost of CVT repair or replacement and the lack of available resources for DIY repairs.
Takeaways
- 🔧 The continuously variable transmission (CVT) in Nissan Murano is a transaxle designed for front-wheel drive with a transmission cooler and manual valve for gear selection.
- 🔩 The CVT system is compact, with primary and secondary pulleys connected by a belt, and a countershaft that goes to the differential.
- 💡 The transmission control module (TCM) manages the hydraulic and electrical aspects of the CVT, receiving inputs from various vehicle components and controlling the hydraulic circuits.
- 🛠️ The CVT's variator system, consisting of input and output pulleys, adjusts the effective diameter of the pulleys to vary the transmission ratio, providing low gear ratios for starting and high gear ratios for highway driving.
- 🔥 One of the common failure modes of Nissan CVTs is the steel belt, which can fail under high torque loads, especially in higher-powered vehicles.
- 🚿 Inadequate cooling systems can lead to overheating and accelerated wear in CVTs, causing parts to disintegrate faster.
- 🛢️ Regular transmission fluid and coolant changes are crucial for prolonging the life of a CVT, as there are no partial rebuild options like in traditional automatic transmissions.
- 🚫 Nissan CVTs should be driven with care to avoid towing or high-stress conditions that could damage the transmission.
- 💰 The cost of replacing a failed CVT can be significant, often requiring a complete unit replacement rather than repair.
- 🚗 CVTs offer smooth power delivery and better fuel economy than traditional automatics, but this comes at the expense of a 'rubber band' effect on acceleration and increased noise.
- ⚙️ The planetary gear set within the CVT provides reverse functionality, similar to an automatic transmission, and can also be a point of failure.
Q & A
What is the main component of a continuously variable transmission (CVT) that allows it to vary the gear ratio?
-The main component that allows a CVT to vary the gear ratio is the pulley system, which consists of input and output pulleys with a steel belt connecting them. The effective diameter of these pulleys is adjusted to change the gear ratio.
Why are CVTs typically associated with lightweight or economy vehicles?
-CVTs are typically associated with lightweight or economy vehicles because they offer smooth power delivery and better fuel economy due to the lack of traditional gears and reduced friction. However, they are not usually used in high-powered vehicles due to their potential limitations in handling high torque loads.
What is the function of the torque converter in an automatic transmission?
-The torque converter in an automatic transmission serves to transfer the engine's torque to the transmission smoothly and efficiently. It also provides a fluid coupling between the engine and transmission, allowing for smoother starts and load changes without any interruption in power.
How does the design of the CVT's steel belt contribute to its flexibility and strength?
-The CVT's steel belt is composed of small, individual pieces of steel that form a flexible yet strong band. The design allows the belt to be flexible enough to move around the pulleys while maintaining the strength necessary to transfer torque from the engine to the wheels.
What are some potential failure modes of a CVT?
-Some potential failure modes of a CVT include the belt wearing out or breaking due to high torque loads, variators not adjusting properly leading to slipping or shuddering, and inadequate cooling leading to overheating and accelerated wear of components.
Why is the cooling system of a CVT considered inadequate in some Nissan models?
-The cooling system in some Nissan CVT models is considered inadequate because it may not be able to keep up with the heat generated by the high torque loads, especially when paired with powerful engines. This can lead to parts disintegrating and wearing out faster, reducing the lifespan of the transmission.
What is the main advantage of a CVT in terms of fuel economy?
-The main advantage of a CVT in terms of fuel economy is the smooth and continuous power delivery without the need for gear shifts. This results in less friction and more efficient use of the engine's power, leading to better fuel efficiency.
How does the planetary gear set in a CVT contribute to the transmission's operation?
-The planetary gear set in a CVT provides the reverse direction function, allowing the vehicle to back up. It also locks the ring gear to the sun gear, enabling the transmission to engage in reverse or drive modes.
What is the difference between the hydraulic and electric actuation systems used in CVTs?
-Hydraulic actuation systems in CVTs use oil pressure to adjust the width of the variators, changing the effective diameter of the pulleys. Electric servo motors, on the other hand, move the variators in and out to achieve the same effect, but are not present in the CVT discussed in the script.
Why are there fewer solenoids in a CVT compared to a typical automatic transmission?
-There are fewer solenoids in a CVT because there are fewer clutches inside the transmission. The hydraulic circuits in a CVT are simpler due to the absence of multiple gear sets and clutch packs, reducing the number of solenoids needed.
What is the significance of the transmission control module in a CVT?
-The transmission control module (TCM) in a CVT is responsible for interfacing with other vehicle computers through the CAN communication bus. It processes inputs like accelerator position and wheel speed to compute and generate electrical signals that control the operation of the CVT, such as adjusting the pulleys' diameters.
Outlines
🔧 Exploring the Insides and Workings of a CVT from a Nissan Murano
The video begins with an introduction to the continuously variable transmission (CVT) found in a Nissan Murano, highlighting its transaxle design for front-wheel drive. The presenter outlines the components of the CVT, including the torque converter, transmission cooler, manual valve, speed sensor, and variators. The disassembly process starts with removing hoses, the cooler, and the filter, which is similar to a car's oil filter but smaller. The video emphasizes the importance of the valve body, which directs fluid flow for various transmission operations. The presenter also discusses the electronic components, such as the EPROM and transmission control module, which manage the CVT's functions. The hydraulic aspects are also covered, explaining how the transmission control module converts electronic inputs into hydraulic outputs to adjust the pulleys and gear ratios.
🔩 Dissecting the CVT's Components and Understanding Their Functions
The presenter continues by removing bolts to access the transmission's interior, revealing the input shaft, oil pump, and differential. The CVT's unique features, such as the variator and steel belt, are explained, with a focus on how they contribute to the transmission's smooth operation. The video also covers the planetary gear set's role in providing reverse functionality. The oil pump's design and operation are detailed, including its internal fluid passages and pressure regulation. The presenter then discusses the CVT's parking pawl mechanism and the process of removing the oil pump and housing. The heart of the CVT, including the input and output pulleys and the steel belt, is examined, with an explanation of how the pulleys adjust their effective diameter to vary the transmission ratio for different driving conditions.
🔄 Understanding the CVT's Pulleys and Belt System for Gear Ratio Adjustment
The video delves into the operation of the CVT's pulleys and belt, describing how the pulleys' conical shape allows for the adjustment of the effective diameter and, consequently, the gear ratio. The presenter explains the hydraulic actuation system that adjusts the pulleys' widths, enabling the CVT to maintain a constant belt length despite changes in diameter. The removal of the pulleys and the examination of the belt's construction, made of small steel pieces forming a flexible yet strong band, are shown. The video contrasts the push-style system of the CVT belt with the pull-style system of a rubber belt, emphasizing the belt's role in torque transfer and its response to hydraulic pressure changes.
⚙️ Failure Modes of CVTs and Their Impact on Vehicle Performance
The final paragraph addresses common failure modes of CVTs, focusing on the belt as the weakest link due to its steel construction and the high torque it must handle, especially in more powerful vehicles like the Nissan Murano. The video discusses how wear and tear, improper variator adjustments, and inadequate cooling systems can lead to belt slippage, shuttering, and even transmission failure. The presenter also contrasts the CVT's smooth power delivery and fuel efficiency with its drawbacks, such as noise and the rubber band effect during acceleration. The video concludes with advice on maintaining a CVT, including regular fluid changes and cautious driving, and a cautionary note on the high replacement costs and lack of rebuild options for CVTs.
Mindmap
Keywords
💡Continuously Variable Transmission (CVT)
💡Torque Converter
💡Valve Body
💡Transmission Control Module (TCM)
💡Pulleys and Belt
💡Hydraulic Actuators
💡Planetary Gear Set
💡Oil Pump
💡Cooling System
💡Failure Modes
💡Fuel Economy
Highlights
The video provides an in-depth look inside a continuously variable transmission (CVT), explaining its components and operation.
The CVT from a Nissan Murano is used as an example, which is a transversely situated transaxle for front wheel drive.
A transmission cooler and manual valve are identified, highlighting the CVT's cooling and gear selection mechanisms.
The disassembly process reveals the hydraulic control system, including solenoids and pressure regulators, which adjust pulley sizes.
The electronic aspects of the CVT are discussed, including the transmission control module and its connection to the vehicle's computer system.
The steel belt in the CVT is shown to be flexible yet strong, made of small steel pieces that transfer torque between pulleys.
The variator's role in adjusting the effective diameter of the pulleys is demonstrated, affecting the transmission's gear ratio.
The video points out that Nissan has paired CVTs with higher-powered engines, which can lead to increased stress and failure.
Cooling system inadequacies in Nissan CVTs are discussed as a significant oversight, leading to faster wear and potential failure.
A whining sound is identified as a telltale sign of CVT failure, due to steel-on-steel contact within the transmission.
The advantages of CVTs, such as smooth power delivery and better fuel economy, are contrasted with their disadvantages, like noise and a 'rubber band' effect.
Nissan markets CVTs as more reliable due to fewer moving parts, but the video disputes this claim, citing numerous failures and legal issues.
The high cost of replacing a CVT, as opposed to rebuilding an automatic transmission, is mentioned as a significant drawback.
The video concludes with advice for CVT owners, emphasizing regular transmission fluid changes and gentle driving to prolong the transmission's life.
A unique aspect of the video is the use of the presenter's brother's old pants and gym pants to clean up the transmission fluid, adding a humorous touch.
The presenter's DIY approach to disassembling the CVT, including using an angle grinder to remove parts, demonstrates the complexity of these transmissions.
The video provides a visual breakdown of the CVT's components, such as the input and output actuators, and the planetary gear set.
The importance of the CVT's oil pump and its role in providing fluid flow for transmission operation is explained.
Failure modes of the CVT, including belt failure and improper variator adjustments, are explored in detail.
Transcripts
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