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2018 IS 300 Transmission Hesitation & Rough Downshifts

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Chris P. · rep 0 · May 22, 4:46 AM · 1 replies · solved · Question

Vehicle: 2018 Lexus IS 300 F Sport

Hey everyone, I'm looking for some advice on my 2018 Lexus IS 300 F Sport. Lately, I've noticed the transmission seems to hesitate when accelerating from a stop, almost like a delay before it engages. Also, when slowing down, especially from 3rd to 2nd gear, it sometimes has a noticeably rough or clunky downshift. It's not constant, but it's happening more frequently.

The car has about 60,000 miles, and I'm wondering if this is a known issue for the 8-speed automatic transmission in these models. Could it be a software problem, or something more serious like a solenoid or fluid issue? I'm trying to figure out if this is normal 'character' for the transmission or if I should be concerned.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:46 AM

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ClearTheCode admin answer:

Transmission hesitation and rough downshifts in a 2018 Lexus IS 300 F Sport with 60,000 miles are symptoms that warrant investigation. While modern automatic transmissions can sometimes exhibit unique shift characteristics, consistent hesitation or harshness usually indicates an underlying issue. Here's what to consider:

  1. Transmission Fluid Condition: The 8-speed automatic transmission in your IS 300 uses a specific WS (World Standard) fluid. Over time and mileage, transmission fluid can degrade, losing its lubricating and heat-dissipating properties. While Lexus often states 'lifetime' fluid, many technicians recommend a fluid drain and fill (not a flush) around 60,000-80,000 miles, especially if you're experiencing shift quality issues. Low fluid levels can also cause problems.

  2. Software/Adaptive Learning: Modern transmissions are controlled by a Transmission Control Module (TCM) that 'learns' your driving style. Sometimes, this adaptive learning can lead to undesirable shift patterns. A dealership can check for updated software calibrations for your TCM. They can also perform a 'reset' of the adaptive values, allowing the transmission to relearn from scratch, which often smooths out shifts.

  3. Solenoid Issues: The transmission uses various solenoids to control fluid flow and engage different gears. If a solenoid is sticking or failing, it can cause delayed engagement, harsh shifts, or slipping. A diagnostic scan by a Lexus technician can often reveal specific trouble codes (DTCs) related to transmission solenoid performance, such as P0751 (Shift Solenoid 'A' Performance) or P0776 (Pressure Control Solenoid 'B' Performance).

  4. Valve Body Problems: Less commonly, issues within the transmission's valve body (which directs fluid pressure to the clutches and bands) can cause these symptoms. This is a more involved repair.

When to See a Shop: It's highly recommended to have your Lexus IS 300 inspected by a Lexus dealership or a reputable transmission specialist. They can perform a diagnostic scan to check for any stored transmission-related trouble codes, inspect the transmission fluid, and determine if a software update, adaptive reset, or a more significant repair (like solenoid replacement) is needed. Addressing these issues early can prevent more extensive and costly transmission damage.

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