2007 Nissan Sentra Transmission

Alright, let's dive into the transmission found in the 2007 Nissan Sentra. Understanding this component is crucial for both basic maintenance and more advanced troubleshooting. We'll cover the different types available, their common issues, and what you should know if you're planning any repairs or even a swap.

Available Transmissions

The 2007 Sentra primarily came with two transmission options:

• RE0F10A Continuously Variable Transmission (CVT): This was the most common option, designed for fuel efficiency and smooth acceleration.
• 6-Speed Manual Transmission (RS6F52A): Available on specific trims, offering a more engaging driving experience.

We'll dissect each of these in detail.

RE0F10A CVT: The Fuel Sipper

The RE0F10A is a continuously variable transmission, or CVT. Unlike traditional automatic transmissions with fixed gear ratios, a CVT utilizes a system of belts and pulleys to provide an infinite range of gear ratios within its operating range. This allows the engine to constantly operate at its most efficient RPM, leading to better fuel economy. In the Sentra, this CVT is electronically controlled for optimal performance. Understanding its functionality is crucial for proper maintenance and troubleshooting.

Key Components:

• Input Pulley (Primary Pulley): Connected to the engine.
• Output Pulley (Secondary Pulley): Connected to the differential and drive axles.
• Steel Belt (Push Belt): Connects the two pulleys and transmits power. It's made of hundreds of interlocking steel elements.
• Valve Body: Contains solenoids that control hydraulic pressure, which in turn adjusts the pulley ratios. Think of it as the brain controlling the gear ratios.
• Transmission Control Module (TCM): Receives signals from various sensors (e.g., engine speed, vehicle speed, throttle position) and commands the valve body.
• Oil Pump: Provides hydraulic pressure for the entire system.
• Torque Converter: Allows the engine to idle without stalling and provides some torque multiplication at low speeds. Similar to a traditional automatic transmission.

How it Works:

The TCM analyzes data from various sensors and uses this information to determine the optimal gear ratio for the current driving conditions. It then signals the valve body to adjust the hydraulic pressure acting on the pulleys. The pulleys are designed to change their effective diameter based on this pressure. As the diameter of one pulley increases, the diameter of the other pulley decreases, effectively changing the gear ratio. The steel belt transmits the power between the pulleys. This continuous adjustment allows for seamless transitions and optimal engine performance.

Common Issues:

Juddering/Shuddering: This is a common complaint with the RE0F10A. It often occurs during acceleration or at low speeds. This can be caused by several factors: degraded CVT fluid, worn steel belt, or issues with the valve body. Regular CVT fluid changes are critical to prevent this issue.

Slipping: When the transmission slips, the engine revs up without a corresponding increase in vehicle speed. This indicates a loss of friction within the transmission, often due to a worn steel belt or low fluid levels. Severe slipping can lead to permanent damage.

Overheating: CVTs generate heat, and if the cooling system is inadequate or the fluid is degraded, the transmission can overheat. This can damage internal components and lead to premature failure. Look for transmission warning lights on your dashboard.

Valve Body Issues: The valve body is a complex component with numerous solenoids that can fail over time. This can lead to erratic shifting, poor performance, and diagnostic trouble codes (DTCs).

Maintenance:

• CVT Fluid Changes: This is the most important maintenance item. Use only the specified Nissan CVT fluid (Nissan NS-2, now superseded by NS-3). The recommended interval is typically every 30,000 miles under normal driving conditions, or more frequently under severe conditions. Do not use regular automatic transmission fluid!
• Inspect for Leaks: Regularly check the transmission for any signs of leaks. Address any leaks promptly to prevent fluid loss and potential damage.
• Monitor Transmission Temperature: If you frequently tow or drive in hot conditions, consider installing a transmission temperature gauge to monitor the temperature and take preventative measures if it gets too high.

RS6F52A 6-Speed Manual: The Driver's Choice

The RS6F52A is a traditional 6-speed manual transmission. It offers a more direct and engaging driving experience compared to the CVT. It's also generally considered more reliable, but still requires proper maintenance.

Key Components:

• Input Shaft: Receives power from the engine via the clutch.
• Output Shaft: Transmits power to the differential and drive axles.
• Gears: Sets of gears with different ratios that provide different levels of torque and speed.
• Shift Forks: Move the synchronizers to engage the desired gear.
• Synchronizers: Allow smooth gear changes by matching the speeds of the gears before they engage.
• Differential: Allows the wheels to rotate at different speeds when turning.

How it Works:

The driver selects the desired gear using the shift lever. This moves the shift fork, which in turn engages the synchronizer. The synchronizer matches the speed of the selected gear to the speed of the output shaft. Once the speeds are matched, the gear is engaged, and power is transmitted through that gear to the output shaft. The output shaft then drives the differential, which distributes power to the drive axles.

Common Issues:

Grinding Gears: This usually indicates worn synchronizers. It can also be caused by improper clutch adjustment or worn clutch components. If you hear grinding when shifting, especially between certain gears, it's a sign of trouble.

Difficulty Shifting: This can be caused by several factors, including a worn clutch, damaged shift linkage, or low transmission fluid. Start by checking the clutch and shift linkage for proper adjustment.

Popping Out of Gear: This indicates worn gears or damaged synchronizers. It can also be caused by a bent shift fork.

Noisy Operation: Excessive noise, such as whining or humming, can indicate worn bearings or gears. This noise often changes with vehicle speed or gear selection.

Maintenance:

• Manual Transmission Fluid Change: Replace the transmission fluid at the recommended interval (typically every 60,000 miles). Use the correct type of fluid specified in your owner's manual. Using the wrong fluid can damage the transmission.
• Clutch Adjustment: Periodically check and adjust the clutch pedal free play. This ensures proper clutch engagement and disengagement.
• Inspect Shift Linkage: Check the shift linkage for any signs of wear or damage. Replace any worn or damaged components.

Troubleshooting Tips (Both Transmissions)

Before jumping to conclusions, here are some general troubleshooting steps:

• Check Fluid Levels: This is the easiest and most important step. Low fluid levels can cause a variety of problems.
• Scan for Diagnostic Trouble Codes (DTCs): Use an OBD-II scanner to check for any stored trouble codes. These codes can provide valuable clues about the nature of the problem.
• Inspect Wiring and Connectors: Check the wiring and connectors for any signs of damage or corrosion. Clean and reconnect any loose connections.
• Consult a Repair Manual: A repair manual specific to the 2007 Nissan Sentra will provide detailed diagnostic procedures and repair instructions.

Conclusion

The transmission is a critical component of your 2007 Nissan Sentra. Understanding its operation and performing regular maintenance can help to prevent costly repairs. Remember to always use the correct type of fluid and follow the manufacturer's recommended maintenance schedule. If you're unsure about any aspect of transmission maintenance or repair, it's always best to consult with a qualified mechanic.