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Rough Shifting After Transmission Fluid Change on 2018 Sorento V6

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Mark S. · rep 0 · May 25, 2:11 AM · 1 replies · solved · Question

Vehicle: 2018 Kia Sorento EX V6

Hey everyone,

I recently decided to do a DIY transmission fluid drain and fill on my 2018 Kia Sorento EX V6 with about 85,000 miles. I used the recommended OEM fluid and followed a guide I found online. Everything seemed straightforward, but now I'm noticing some rougher shifts, especially between 2nd and 3rd gear, and sometimes a slight hesitation when accelerating from a stop.

Could I have done something wrong? I made sure to measure the fluid I drained and put in the same amount, then checked the level according to the manual (engine warm, cycling through gears). I'm worried I might have introduced air or used the wrong procedure for my specific model. Any advice would be greatly appreciated before I take it to a shop.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 2:11 AM

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ClearTheCode admin answer:

It's commendable that you tackled a transmission fluid change yourself! Rough shifting after a fluid change can be concerning, but it's often rectifiable. Here's a breakdown of potential causes and steps to take:

  1. Verify Fluid Level and Type:

    • Level Check: Re-check the transmission fluid level meticulously. Kia transmissions are very sensitive to correct fluid levels. Ensure the engine is at operating temperature, the vehicle is on level ground, and you've cycled through all gears (P, R, N, D, L) briefly before checking in P or N (consult your owner's manual for the exact procedure for your 2018 Sorento).
    • Fluid Type: Double-check that the fluid you used is exactly the specification required by Kia for your 2018 Sorento V6 (e.g., SP-IV, SP-IV RR). Using an incorrect fluid, even if it seems similar, can cause shifting issues.

  2. Air in the System/Fluid Circulation:

    • Sometimes, after a fluid change, it takes a little driving for the new fluid to fully circulate and for any trapped air to work its way out. Drive gently for a few days to see if it improves. However, if the issue is severe, do not continue driving extensively.

  3. Potential Causes for Rough Shifting:

    • Incorrect Fluid Level: This is the most common culprit. Both overfilling and underfilling can cause problems.
    • Contamination: Though less likely with new fluid, any debris introduced during the process could cause issues.
    • Improper Drain/Fill: If the procedure wasn't followed precisely, or if the system wasn't adequately flushed (if a full flush was attempted), residual old fluid or air could be problematic.
    • Adaptive Learning: Your vehicle's transmission control module (TCM) might need to 're-learn' shift points with the new fluid. This usually happens automatically over time.

  4. When to See a Shop:

    • If the rough shifting persists or worsens after re-checking the fluid level and driving gently for a short period.
    • If you notice any new leaks, strange noises, or the check engine light illuminates (though less common for just fluid issues, it can indicate a deeper problem).
    • If you are unsure about the fluid level or type, or if you suspect you might have introduced contaminants.

An authorized Kia service center or a reputable transmission specialist can perform a diagnostic check, verify the fluid level and condition, and potentially reset the transmission's adaptive learning values if needed.

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