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2020 GX 460 Harsh Shifting & Hesitation - Transmission Concern

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Mike T. · rep 0 · May 25, 3:30 AM · 1 replies · solved · Question

Vehicle: 2020 Lexus GX 460 Premium

Hi everyone, I'm experiencing some concerning transmission behavior in my 2020 Lexus GX 460, which has about 35,000 miles on it. Lately, I've noticed harsh shifts, particularly from 1st to 2nd gear and sometimes downshifting when coming to a stop. There's also an occasional hesitation when accelerating from a standstill.

It's not constant, but it's happening frequently enough to make me worried. I'm still within the factory warranty period, thankfully. Has anyone with a 2020 or similar model year GX 460 experienced these kinds of transmission issues? Is this a known problem, or could it be related to fluid levels or a software glitch?

I'm planning to take it to the dealership, but I'd like to go in armed with some knowledge. Any advice on what to mention or what they might look for would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:30 AM

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ClearTheCode admin answer:

Harsher shifting and hesitation in your 2020 Lexus GX 460's transmission are definitely symptoms that warrant professional attention, especially with only 35,000 miles. While the GX 460's 6-speed automatic is generally robust, these symptoms can indicate various issues. Since you're still under warranty, it's crucial to get this documented and inspected by a Lexus dealership.

  1. Potential Causes for Harsh Shifting/Hesitation:

    • Low or Contaminated Transmission Fluid: Even in a sealed transmission, fluid levels can sometimes be low from the factory or due to a small leak. Contaminated or degraded fluid can also lead to poor shifting.
    • Transmission Control Module (TCM) Software: The TCM manages shift points and pressures. An outdated or glitched software calibration can cause erratic shifting. Lexus might have updated software available to address known shift quality concerns.
    • Solenoid Issues: Solenoids within the valve body control the flow of transmission fluid to engage gears. A faulty or sticking solenoid can lead to harsh shifts or delays.
    • Valve Body Problems: The valve body is the 'brain' of the automatic transmission, directing fluid pressure. Wear or contamination in the valve body can cause a range of shifting problems.
    • Internal Mechanical Wear: Less likely at this mileage, but wear in clutch packs or other internal components could also contribute.

  2. Relevant OBD-II Codes: If the transmission control unit detects an anomaly, it will typically store diagnostic trouble codes (DTCs) related to the transmission. Look for codes in the P07xx series, which specifically relate to transmission control system issues. Examples include:

    • P0700: Transmission Control System Malfunction (a general code indicating a transmission issue exists).
    • P0705: Transmission Range Sensor Circuit Malfunction.
    • P0720: Output Speed Sensor Circuit Malfunction.
    • P0731 - P0736: Incorrect Gear Ratio for specific gears.

When to See a Shop:

Take your GX 460 to a Lexus dealership immediately. Since you are under warranty, any necessary repairs should be covered. Clearly describe the symptoms (when they occur, which gears, acceleration vs. deceleration) to the service advisor. They will connect to the vehicle's computer to check for stored transmission codes, inspect fluid levels and condition, and check for any applicable Technical Service Bulletins (TSBs) or software updates related to transmission performance for your specific model year. Do not delay, as transmission issues can worsen over time.

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