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New TSB L-SB-0048-25 for transmission downshift clunk

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Old Oct 24, 2025 | 09:18 AM
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Default New TSB L-SB-0048-25 for transmission downshift clunk

Just saw someone posted this over at reddit. If someone had it done already, any issues afterwards?

The description sounds like what I'm experiencing when slowing/coasting to a stop for 5-4 or 5-3 downshifts although its less noticable after 10-15 minutes of warmup.
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Old Oct 24, 2025 | 09:28 AM
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^^^ I googled that TSB and it appears to be for the GX 550 and a hood flutter issue. Correct me, if I'm wrong.
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Old Oct 24, 2025 | 09:43 AM
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Just released yesterday apparently so probably why nothing shows up on google. Post with screenshot of the TSB: https://www.reddit.com/r/Lexus/comme...wnshift_clunk/
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Old Oct 24, 2025 | 10:37 AM
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Amazing news. I always had a bad feeling about that noise.
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Old Oct 24, 2025 | 12:29 PM
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I was wondering when this TSB would come out and I it is reassuring to know others are hearing/feeling this same issue.


For those that have reflashed ECUs, do you think this will erase your existing tune?
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Old Oct 24, 2025 | 01:46 PM
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This is just an excuse for service techs to drive the car.

On a related note, if they can do this, why not reprogram the transmission altogether to make it more zippy?
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Old Oct 24, 2025 | 03:22 PM
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Originally Posted by V8Brah
This is just an excuse for service techs to drive the car.

On a related note, if they can do this, why not reprogram the transmission altogether to make it more zippy?
Dumb answer? Cause they hate fun.

Serious answer? Wear management strategy.
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Old Oct 24, 2025 | 03:28 PM
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So it looks like if you don't have this happening, there is no reason to take it in for service, correct?
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Old Oct 24, 2025 | 03:30 PM
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Originally Posted by ExLexOwner
So it looks like if you don't have this happening, there is no reason to take it in for service, correct?
You don't have it? Lucky.

I guess not. I wouldn't bother unless it's an issue for you. If nothing else, it seems like this issue doesn't grenade the transmission after a few thousand miles (if mine is anything to go by). Mine has done it since day 1, over 2.5 years and 23,000 miles ago.
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Old Oct 24, 2025 | 03:39 PM
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Originally Posted by arentz07
Dumb answer? Cause they hate fun.

Serious answer? Wear management strategy.
I would argue a well-tuned transmission would cause less wear because when you mash the pedal everything is just smoother - I could be wrong though.

Toyota/Lexus is such a mess. Their inconsistency when it comes to listening to customers is absolutely infuriating. Follow my logic:

(+) they come out with the IS500 (V8)
(-) they keep a 10 year old interior and transmission
(+) they extend the life of the IS in 2026
(-) they make the exterior worse
(+) they update the interior
(-) they drop the V8 from the next IS
(+) they release a TSB for the IS500 transmission

That's just the IS lineup in a nutshell. Don't even get me started on their boneheaded decisions regarding the ES, RC, LS, and GS.
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Old Oct 24, 2025 | 04:38 PM
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Originally Posted by V8Brah
I would argue a well-tuned transmission would cause less wear because when you mash the pedal everything is just smoother - I could be wrong though.

Toyota/Lexus is such a mess. Their inconsistency when it comes to listening to customers is absolutely infuriating. Follow my logic:

(+) they come out with the IS500 (V8)
(-) they keep a 10 year old interior and transmission
(+) they extend the life of the IS in 2026
(-) they make the exterior worse
(+) they update the interior
(-) they drop the V8 from the next IS
(+) they release a TSB for the IS500 transmission

That's just the IS lineup in a nutshell. Don't even get me started on their boneheaded decisions regarding the ES, RC, LS, and GS.
Keep in mind the TSB says something specifically about the "fuel cut logic", so I don't know whether that would have anything to do with the overall performance of the transmission.

edit: OK I reread it, and it also mentions the transmission control unit. Hmm.

Last edited by arentz07; Oct 24, 2025 at 04:45 PM.
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Old Oct 24, 2025 | 04:51 PM
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I am not sure I understand what you guys are experiencing/describing - It is likely a sign that I don't have it or that I just assume it is part of how this thing is
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Old Oct 24, 2025 | 06:26 PM
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There is a simple fix for this - drive it in sports plus mode and drive it like a V8. I am averaging 16mpg and I rarely run into this.
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Old Oct 24, 2025 | 10:18 PM
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Originally Posted by V8Brah
This is just an excuse for service techs to drive the car.

On a related note, if they can do this, why not reprogram the transmission altogether to make it more zippy?
I remember they came out with something like this for one of my Minis and after the update the car felt lazy as hell! It was a completely different car afterwards and just plain sucked. I'd be careful with this TSB .
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Old Oct 24, 2025 | 10:46 PM
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Originally Posted by Benibiker1558
I remember they came out with something like this for one of my Minis and after the update the car felt lazy as hell! It was a completely different car afterwards and just plain sucked. I'd be careful with this TSB .
This crossed my mind too since they botched the front apron separation TSB. I think I'll wait for the reports from others before going myself.

Sad you can't trust Lexus anymore.
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