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2018 Q50 3.0t Rough Shifting After DIY Transmission Fluid Level Check

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Emily N. · rep 0 · May 22, 5:08 AM · 1 replies · solved · Question

Vehicle: 2018 Infiniti Q50 3.0t Luxe

Hey everyone,

I have a 2018 Infiniti Q50 3.0t Luxe with about 70,000 miles. Recently, I decided to check my transmission fluid level myself, following a YouTube video. I made sure the car was warm and on level ground, but I'm not sure if I got the temperature exactly right. I added a little fluid because it looked low.

Now, the car feels like it's shifting a bit rougher, especially between 2nd and 3rd gear, and sometimes when downshifting. It wasn't doing this before. Did I mess something up? Is there a specific procedure for these transmissions that I missed? Should I be worried, or does it just need to settle?

Any advice would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 5:08 AM

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ClearTheCode admin answer:

It sounds like you might have encountered a common issue when checking or topping off transmission fluid on modern Infiniti vehicles, especially the Q50. The rough shifting you're experiencing could be due to an incorrect fluid level or air introduced into the system.

Here's what you should consider:

  1. Precise Fluid Level Check: Infiniti transmissions (like many modern automatics) are very sensitive to fluid levels. The correct procedure often involves checking the fluid at a very specific temperature range (usually around 100-120°F or 38-49°C) using a diagnostic tool to monitor the transmission fluid temperature (TFT). The engine must be running, and the vehicle must be perfectly level. Overfilling can be just as detrimental as underfilling.
  2. Fluid Type: Ensure you used the exact specified transmission fluid. For your 2018 Q50, it typically requires Nissan Matic S fluid. Using an incorrect fluid type can lead to shifting issues and long-term transmission damage.
  3. Air in the System: If the fluid was significantly low, or if the fill procedure allowed air to enter the system, it could cause temporary shifting anomalies. Driving the car gently for a bit might help purge some air, but this is less common with simple top-offs.
  4. Adaptive Learning: Transmission control modules (TCMs) have adaptive learning. Sometimes, after fluid changes or level adjustments, the TCM needs to relearn optimal shift points. This usually resolves itself after some driving.

When to see a shop:

  • If the rough shifting persists or worsens after a few days of normal driving.
  • If you notice any new warning lights on your dashboard.
  • If you're unsure about the fluid type you used or the accuracy of your fluid level check.
  • A professional can perform a proper fluid level check using a scan tool to monitor TFT and ensure the level is spot on. They can also check for any stored transmission-related diagnostic trouble codes (DTCs) that might not trigger a check engine light but indicate an internal issue.
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