The Infiniti Q40, known for its smooth performance, can sometimes experience shifting issues due to a faulty valve body. This comprehensive guide provides a detailed walkthrough of the Infiniti Q40 Valve Body replacement process for the 2014-2016 models equipped with the VQ37VHR engine and RE7R01A transmission. This issue often presents with a P0720 trouble code, indicating a problem with the output speed sensor circuit. While the sensor itself is rarely the cause (see NHTSA report: https://static.nhtsa.gov/odi/tsbs/2019/MC-10168892-0001.pdf), the valve body is a common culprit.
Understanding the Problem: Symptoms and Diagnosis
A malfunctioning Infiniti Q40 valve body can manifest in several ways:
- P0720 Trouble Code: This code indicates a problem with the output speed sensor circuit, often pointing to the valve body.
- Limited Shifting: The vehicle may not shift beyond third gear.
- Restricted RPM: Engine speed may be capped at 2,000 RPM in first gear.
- Manual Mode Unavailable: Inability to engage manual shift mode.
Gathering the Necessary Tools and Parts
Before starting the replacement, ensure you have the following:
- Replacement Valve Body: A new, rebuilt, or used valve body (eBay is a potential source).
- Nissan Matic S Fluid (999MP-MTS00P): Approximately 10 quarts; using OEM fluid is crucial. Consider purchasing extra. (Z1 Motorsports is a potential source)
- New Drain Bolt: Part Number 31377-31X06
- New Fill Bolt: Part Number 31361-1XJ0A
- New Oil Pan Gasket: Part Number 31397-1XJ0A
- ATF Filler Adapter: CTA Tools 7425 is recommended.
- 5mm Hex Bit: For the fill bolt (not Torx).
- Torque Wrench: Capable of reading as low as 5 ft-lbs.
- Sockets: 19mm for the drain bolt, 10mm for other bolts.
- Fluid Transfer Pump: Harbor Freight offers a suitable option.
- Jack Stands and Jack (or Lift): Ensuring the vehicle is level is crucial.
- A Second Person: Highly recommended to assist with the process.
- Factory Service Manual (FSM): Indispensable for detailed diagrams and instructions (NICOclub is a potential source key pages TM-121, TM-122, TM-219 – TM-222).
Infiniti Q40 Valve Body Replacement Procedure
This process is complex and requires careful attention to detail. Consult the FSM throughout the procedure. The following steps provide a general overview:
Preparation and Removal
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Remove Engine Cover and Drain ATF: Refer to the FSM for specific instructions.
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Remove Exhaust and Sensor Components: Disconnect oxygen sensors and remove necessary brackets as per FSM guidance.
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Remove Oil Pan: Carefully remove the oil pan, gasket, and magnets. Clean thoroughly.
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Access Valve Body: Remove the snap ring, push the joint connector, and disconnect the output speed sensor.
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Remove Valve Body Bolts: Carefully remove the bolts securing the valve body and TCM, paying attention to different sizes and labeling them for reinstallation. Refer to the FSM for bolt locations and torque specifications.
Installation
- Transfer Necessary Parts: Compare the old and new valve bodies and transfer components like the solenoid cover, TCM harness, and joint connector bracket as needed.
- Install New Valve Body: Carefully align the valve body, ensuring proper engagement of the manual valve cutout and projection plate. Consult the FSM for detailed guidance.
- Install Bolts and Tighten: Install and torque the bolts in the correct sequence and to the specified torque, starting with the “E” bolt. Refer to the FSM for specific torque values.
- Reinstall Oil Pan: Install a new oil pan gasket and tighten the bolts to the specified torque.
- Refill ATF: Follow the FSM’s detailed fluid filling procedure, which involves a specific sequence of filling, running the engine, and checking the fluid level. This ensures proper fluid level and avoids damage to the transmission.
Conclusion
Replacing the Infiniti Q40 valve body is a challenging task best left to experienced mechanics. However, with the right tools, thorough preparation, and meticulous adherence to the FSM, a skilled DIYer can accomplish this repair. Remember, safety and accuracy are paramount. Always prioritize safety and consult the FSM for comprehensive instructions and diagrams. Successfully completing this process will restore your Q40’s smooth shifting and optimal performance.
