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2018 Lexus RX 350 Transmission Hesitation and Rough Shifting

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Brittany E. · rep 0 · May 22, 4:40 AM · 1 replies · solved · Question

Vehicle: 2018 Lexus RX 350 F Sport

Hey everyone, I'm experiencing some really frustrating issues with my 2018 Lexus RX 350 F Sport. Lately, the transmission feels like it's hesitating quite a bit, especially when accelerating from a stop or at lower speeds. It's almost like there's a delay before it engages properly.

On top of that, I've noticed some rough shifts, particularly between 2nd and 3rd gear, and sometimes downshifting feels clunky. It's not consistent, but it's happening more frequently now. There's no check engine light on, which is confusing.

Has anyone else with a similar year RX 350 experienced this? What could be causing this kind of transmission behavior? I'm hoping it's not a major issue.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:40 AM

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ClearTheCode admin answer:

Transmission hesitation and rough shifting in a 2018 Lexus RX 350 can stem from several causes, even without an illuminated check engine light. Modern transmissions are complex, and subtle issues can affect performance.

Common Causes:

  1. Low or Contaminated Transmission Fluid: Over time, transmission fluid can degrade or become low, leading to poor lubrication and increased friction, causing rough shifts and hesitation. Contaminated fluid can also clog internal passages.
  2. Transmission Control Module (TCM) Software Glitch: Sometimes, a simple software update or reset of the TCM can resolve erratic shifting patterns. The TCM learns your driving style, and sometimes this learning can become skewed.
  3. Worn Solenoids or Valve Body Issues: Solenoids control the flow of transmission fluid to engage gears. If they are sticking or failing, it can lead to delayed or harsh shifts. The valve body itself can also develop issues.
  4. Torque Converter Problems: A failing torque converter can cause shuddering, slipping, or delayed engagement, especially when starting from a stop.
  5. Sensor Malfunctions: Speed sensors (input/output) or the transmission fluid temperature sensor can send incorrect data to the TCM, leading to improper shift timing.

What to Do:

  1. Check Transmission Fluid: While many modern transmissions are 'sealed for life,' it's crucial to have a qualified technician check the fluid level and condition. This often requires specific tools and procedures.
  2. Scan for Pending Codes: Even without a Check Engine Light, a professional scan tool can sometimes reveal pending diagnostic trouble codes (DTCs) related to the transmission (e.g., P0700 series codes like P0705, P0715, P0720, or gear ratio errors P0731-P0736) that haven't yet triggered the dashboard light.
  3. Consult a Lexus Specialist: Given the complexity, it's best to have a Lexus dealership or a reputable independent transmission specialist diagnose the issue. They have the specific diagnostic tools and expertise for these vehicles.

When to See a Shop:

Immediately. Transmission issues, even minor ones, can quickly escalate into costly repairs if not addressed promptly. Continuing to drive with these symptoms can cause further damage to internal transmission components. Describe the symptoms in detail to the technician, including when and how often they occur.

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