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2024 Lexus RX 350h — should I service 'lifetime' transmission fluid?

JDMGuy85Community StarterJan 6, 20262024 Lexus RX 350hTexas
2024 Lexus RX 350h, about 96,000 miles. Manual says the transmission fluid is lifetime under normal use, but the car is approaching 80k miles and I plan to keep it a long time. Curious what owners are actually doing and whether drain/fill versus exchange matters. If I fix it I'll come back and update the thread.
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2023 Lexus RX 350 Premium

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11 replies

ApexGuy71Community StarterCommunity StarterJan 6, 2026permalink
I'd want a measurement, not a hunch. Get a real battery/charging test on the 2024 Lexus RX, not just resting voltage, before blaming a module. Save the big job until that test fails. Monthly payment math is how wallets disappear. Trying not to diagnose from the couch.
JDMGuy85Community StarterCommunity StarterJan 7, 2026permalink
I went back under the 2024 Lexus RX and it only happens after a heat soak, not on a cold start. Next check is the cheap one I can do in a driveway.
CityRunner96Community StarterCommunity StarterJan 7, 2026permalink
Log the conditions before you spend. If a shop can't duplicate it on the 2024 Lexus RX, bring a video plus freeze-frame data, not just a story. Save the big job until that test fails. On “should i service 'lifetime' transmission fluid,” that was the fork that mattered for me. This is from a 2024 Lexus RX in Texas with 96,000 miles. If you share a photo of the worksheet, easier to sanity-check. Parking it somewhere I can hear it better next time.
ApexGuy71Community StarterCommunity StarterJan 7, 2026permalink
Fair point. Counterpoint: Loaded-suspension checks on the 2024 Lexus RX catch play that a wheels-hanging inspection misses. Save the big job until that test fails. Parts cannon is a personality type I try to avoid. Your commute and mine probably aren't the same, but the test still applies. I'd rather look cautious in this thread than stuck later.
CityRunner96Community StarterCommunity StarterJan 8, 2026permalink
I'd push back a little: Move a coil or plug on the 2024 Lexus RX if it's cylinder-specific and see whether the code follows. Don't erase codes until someone who can help has seen them. If you share a photo of the worksheet, easier to sanity-check. I'm in no rush to be a hero on it.
ApexGuy71Community StarterCommunity StarterJan 8, 2026permalink
Agree — and I'd add this: Move a coil or plug on the 2024 Lexus RX if it's cylinder-specific and see whether the code follows. That's the branch I'd chase this week. On “should i service 'lifetime' transmission fluid,” that was the fork that mattered for me. The universe charges extra for guessing. If your situation is the opposite, ignore me. I already checked the easy fluid levels.
JDMGuy85Community StarterCommunity StarterJan 7, 2026permalink
Update: the cheap test changed the symptom, so I'm not throwing parts yet. I'm in no rush to be a hero on it.
JDMGuy85Community StarterCommunity StarterJan 7, 2026permalink
Checked the easy stuff on the 2024 Lexus RX and found one clue worth chasing before I book a shop. Parking it somewhere I can hear it better next time.
PixelPilot91Community StarterCommunity StarterJan 7, 2026permalink
Start with the test that can prove you wrong. Swap the cheap/easy piece first on the 2024 Lexus RX and see if the fault moves. Save the big job until that test fails. Write the result down so the next test isn't a repeat of the last one. Your commute and mine probably aren't the same, but the test still applies. Cold start is when I can actually reproduce it.
NewCarCamperCommunity StarterCommunity StarterJan 8, 2026permalink
I wouldn't throw parts yet. Loaded-suspension checks on the 2024 Lexus RX catch play that a wheels-hanging inspection misses. Save the big job until that test fails. Do that first. I've seen both outcomes, which is why I'd test instead of assume. Cold start is when I can actually reproduce it.
PixelPilot91Community StarterCommunity StarterJan 8, 2026permalink
Ask what changed right before it started. Get a real battery/charging test on the 2024 Lexus RX, not just resting voltage, before blaming a module. If the cheap test changes it, stop and reassess. Time, temperature, and whether it's in gear are the notes that actually help a shop. If it repeats twice more I'll book time.
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