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Rough Shifting on my 2018 Q50 3.0t - Time for Transmission Fluid?

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Chris P. · rep 0 · May 22, 5:07 AM · 1 replies · solved · Question

Vehicle: 2018 Infiniti Q50 3.0t

Hey everyone,

I've got a 2018 Infiniti Q50 3.0t with about 75,000 miles on it. Lately, I've noticed the transmission shifting a bit rough, especially between 2nd and 3rd gear, and sometimes when downshifting. It's not always consistent, but it's definitely more noticeable than it used to be.

I've been keeping up with regular oil changes, but I'm not sure if the transmission fluid has ever been changed. I bought the car used a couple of years ago.

Is 75k miles a typical interval for a transmission fluid change on these Q50s? Is this something a reasonably handy DIYer can tackle, or is it best left to a professional given the complexity of modern transmissions? Any specific fluid recommendations or things to watch out for?

Thanks for any advice!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 5:07 AM

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ClearTheCode admin answer:

Rough shifting in your 2018 Infiniti Q50 3.0t at 75,000 miles can indeed be a sign that your transmission fluid is due for attention. While Infiniti often states 'lifetime' fluid for some transmissions, in practice, fluid degrades over time and mileage, especially with performance driving or in hot climates.

Here's what you should consider:

  1. Transmission Fluid Service Interval: For the 7-speed automatic transmission in your Q50, many independent shops and enthusiasts recommend a transmission fluid drain and fill every 60,000 to 90,000 miles, or sooner if you drive aggressively. Infiniti's official stance might be longer, but proactive maintenance is key for longevity.
  2. Causes of Rough Shifting:
    • Degraded Fluid: Over time, transmission fluid loses its lubricating properties and can become contaminated with clutch material, leading to increased friction and rough shifts.
    • Low Fluid Level: A low fluid level can cause pressure issues within the transmission, affecting shift quality.
    • Solenoid Issues: Less commonly, a failing shift solenoid could cause specific gear shifting problems.
    • Software Glitch: Sometimes, a transmission control module (TCM) software update can resolve minor shifting anomalies.
  3. DIY vs. Professional:
    • DIY Drain & Fill: A simple drain and fill is often possible for a DIYer with the right tools and knowledge. You'll need to ensure you use the correct Nissan Matic S or equivalent fluid (check your owner's manual or a reputable parts supplier for the exact specification). Be aware that a drain and fill only replaces a portion of the total fluid.
    • Professional Flush: A full fluid exchange (flush) is more comprehensive but requires specialized equipment. Some shops perform this, but it's crucial to ensure they use the correct method and fluid to avoid potential issues.
    • Complexity: The Q50's transmission can be sensitive to fluid levels and types. If you're not confident, a professional service is recommended. They can also check for any related diagnostic trouble codes (DTCs), though rough shifting often doesn't trigger a specific OBD-II code unless there's a more severe internal issue (e.g., P0700 - Transmission Control System Malfunction).
  4. When to See a Shop:
    • If the rough shifting is accompanied by warning lights (e.g., 'Service Engine Soon' or 'AT Check').
    • If you notice any slipping, grinding, or complete loss of gears.
    • If a fluid change doesn't resolve the issue, or if the fluid looks excessively dark or smells burnt.
    • If you're unsure about performing the service yourself.

Addressing the transmission fluid is a good first step. A professional can also perform a diagnostic scan to check for any underlying electronic issues before proceeding with a fluid service.

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