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2018 RX 350 Transmission Hesitation and Hard Shifts at Low Speeds

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Mike T. · rep 0 · May 25, 3:25 AM · 1 replies · solved · Question

Vehicle: 2018 Lexus RX 350 FWD

Hey everyone,

I've got a 2018 Lexus RX 350 FWD, and I've started noticing some concerning transmission behavior lately. Specifically, when I'm driving at lower speeds, like in stop-and-go traffic or pulling away from a stop sign, the transmission seems to hesitate before engaging, and then sometimes shifts quite hard into the next gear.

It's not constant, but it's happening more frequently now. There's no check engine light on, and the fluid levels seem fine from what I can tell. Has anyone else experienced this with their RX 350, especially around this model year? I'm wondering if it's a common issue or something I should be really worried about.

Any advice or shared experiences would be greatly appreciated before I take it to the dealership. Thanks!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:25 AM

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ClearTheCode admin answer:

Transmission hesitation and hard shifts in a 2018 Lexus RX 350, even without a Check Engine Light (CEL), can indicate several potential issues. It's important to address this promptly to prevent further damage.

Common Causes:

  1. Low or Contaminated Transmission Fluid: Even if the level appears fine, old or burnt fluid can lose its lubricating properties, leading to poor shifting. Contamination can also cause issues.
  2. Transmission Solenoid Problems: Solenoids control fluid flow within the transmission. A failing solenoid can cause delayed or harsh shifts. These may not always trigger an immediate CEL.
  3. Valve Body Issues: The valve body is the 'brain' of the automatic transmission, directing fluid to engage clutches and bands. Wear or blockages in the valve body can lead to erratic shifting.
  4. Software Glitch/Adaptive Learning: Sometimes, the Transmission Control Module (TCM) software can develop glitches or its adaptive learning parameters might need to be reset or updated. Lexus has issued TSBs (Technical Service Bulletins) for some models related to transmission programming.
  5. Torque Converter Problems: While less common for just hesitation, a failing torque converter can contribute to irregular power transfer and shifting issues.

When to See a Shop:

  • Immediately: If the problem worsens, you hear grinding noises, or the vehicle struggles to move.
  • Soon: Even without a CEL, persistent hesitation and hard shifts warrant professional diagnosis. Continuing to drive with a developing transmission issue can lead to more extensive and costly repairs.

Recommended Steps:

  1. Professional Diagnostic Scan: A Lexus-specific diagnostic tool can often pull 'pending' or 'history' codes that a generic OBD-II scanner might miss, or provide live data on transmission parameters.
  2. Transmission Fluid Inspection: Have a technician perform a thorough inspection of the transmission fluid's condition (color, smell, presence of metal particles) and level.
  3. Check for TSBs: Ask the dealership if there are any relevant Technical Service Bulletins or software updates for your specific 2018 RX 350 model regarding transmission performance.
  4. Test Drive with Technician: Replicate the issue with a skilled technician to help them pinpoint the exact symptoms.
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