Transmission Clunk TSB L-SB-0042-25

[Roman]

I started at 16, right after I was around 20-21, settled around 18.6. Every refill now shows >310 miles? When before it was like 298.
I’ll take every mile

Still impressive, I haven't had enough driving since the update to notice myself...
If it does work, I'll take it!

 

[GMan93]

Want to come back and say after having driven a bit more and given the transmission time to re-learn a bit after the update and reset it's much much much better than it was...my clunky 3-2 shift seems almost non-existent now, maybe very occasionally still does it if the right circumstances happen when stopping but more sound wise and not really something you'd feel/notice if the radio is on. The car coasts 1000x better and seems to stay at a fairly consistent RPM level when cruising/up to speed now vs all the gear hunting it was doing before. All-in all a worthwhile update that makes the car drive a lot more like it should have to begin with.

 

[Bluegill]

I also noticed that highway cruising & coasting is improved with less aggressive downshifting. I have previously bitched a lot about how the truck slows itself down so aggressively when you want to coast - for instance, when you're exiting the highway onto a long off ramp. Here in AZ we have some off ramps that are a mile long, or feed onto frontage roads that run for miles. I know that the northeast has exit ramps that give you about 15 feet before you have to crank a hard right 270-degree turn (California too). But out here you can exit the highway at 80 mpg and coast for a long time. I always thought it was absurd that I had to keep shoveling coal onto the fire to make it to the end of an off ramp.

I just did about 400 miles this past week and I noticed a healthy MPG improvement (14.5 indicated which is more like 15.6 corrected for my larger tires). This included going from 1440 feet in elevation to 6800 feet plus over 120 miles of off-road, rocks, mud, climbing, etc.

 

[cmfhsu]

People who have / had this clunk - do you face the clunk only when the transmission is cold? Or does it clunk even when fully warm?

I'm starting to get it at 3000 miles, but only when the transmission is fully cold-soaked overnight. After the transmission reaches operating temperature on the dashboard, my transmission is totally smooth.

 

[RPMSTL]

After the update, my downshifts coming to a stop are smooth.

My 1st cold shift every morning from 1>2 is quite rough. Only does it once.
It is a hesitation followed by a hard shift.

Throttle activated downshifts while accelerating on the highway can sometimes
be rougher than they should be.

I agree that overall it may coast better. There is a 35 mph road I travel daily with some slight
downhill and twisty curves where before the update, the transmission didn't seem to know which
gear to go in. It was constantly shifting, that is better now.

 

[RonV]

At the dealership now, will update when i get it back. The technician says it’s an update.
Just got it back. Smooth as butter! It was getting pretty bad, almost every light. Can already feel the difference!

Had mine updated as well. No more harsh downshift. This is what was mentioned on the invoice:

 

[Cajun Heat]

Had the TSB completed at the 54k/mile service. Put about 600 miles since that and so far so good.

 

[CitizenEarthling]

Had mine updated as well. No more harsh downshift. This is what was mentioned on the invoice:View attachment 16303

I did the same code today.... It's night and day. If you drove the before and after side by side, you would say that it was two different cars.

 

[CitizenEarthling]

View attachment 15481

You're a legend! The bucking was driving me insane....

 

[pmajche1]

My downshift jitter/jolt seems to have returned, even after the software update. Its fairly subtle, but enough to be annoying. Definitely more noticeable prior to warming up to full operating temperature, but still far from perfect at temperature. I plan to have the dealer look at it at the 10k service. Anyone else have the update and not see the results they were expecting?

 

[cmfhsu]

Just had it flashed yesterday, and I still have a minor jolt, though much less noticeable than before. They may also have erased the learned pressure values in the TCU, so it might just be re-learning right now.

If anybody is wondering if recently produced 2025 GXs can have the calibration applied, you can! Mine was produced in July 2025 and I had no problem getting the dealer to flash my ECU.

Make sure you give your dealer the updated TSB number: L-SB-0042-25. The old TSB L-SB-0031-25 was a preliminary one which I believe dealers now cannot access or reference.

 

[incognito.gx]

Tempted to not even have this done at my 10k appt. I don’t really have the harsh downshift ya’ll describe just a little bit of lag when accelerating (at times). I’ll admit the transmission can feel a bit ‘jerky’ but certainly nothing unbearable.

 

[gvan1998]

i only did it because people are reporting improved gas mileage.

 

[RPMSTL]

No improved gas mileage after update for me.

 

[pmajche1]

Tempted to not even have this done at my 10k appt. I don’t really have the harsh downshift ya’ll describe just a little bit of lag when accelerating (at times). I’ll admit the transmission can feel a bit ‘jerky’ but certainly nothing unbearable.

My service tech claimed it should help with the lag and hesitation as well.

 

[ToyCruiser]

It didn't fix mine any more than an ECU reset did.. which is to say that it helped for about 3 days..

 

[cmfhsu]

I truly think greasing my driveshaft helped more than the TSB. It makes the throttle react more immediately, it tames the clunks, and it's straight up healthy for the car.

I'll have to see how the vehicle behaves after a few thousand miles, but I'm quite happy after greasing my slip yoke a second time in 4000 miles.

 

[CitizenEarthling]

I truly think greasing my driveshaft helped more than the TSB. It makes the throttle react more immediately, it tames the clunks, and it's straight up healthy for the car.

I'll have to see how the vehicle behaves after a few thousand miles, but I'm quite happy after greasing my slip yoke a second time in 4000 miles.

Is that easy DIY for a noob?

 

[cmfhsu]

I'd say it's about as difficult as a diy oil change, though more fiddly if you don't have a way to lift all 4 wheels off the ground.

EDIT: Here's a writeup from our very own nartmot describing the process for the GX550 specifically: Anyone know if the GX550 Has Grease-able U-Joints

Here's a YouTube diy for the gx460:

It's more or less the same. Somebody please correct me if I'm wrong, but I believe there's 4 zerks for the u joints (one per), but only one slip yoke zerk fitting on the rear driveshaft (now located on the large section of the driveshaft, seemingly different from the gx460 which is on the small section near the u joint). The front slip yoke seems to have a gaiter and no zerk, but I'd like to hear from anybody who's found a front driveshaft zerk.

I use Lucas red n tacky grease, but the manual says any #2 non-moly lithium grease will work. I filled the u joint grease until all the white / grey factory grease was purged, and I pumped like 13 pumps of grease into the slip yoke and it didn't budge an inch - STOP GREASING THE SLIP YOKE IF YOU SEE IT START TO MOVE OR EXTEND. Greases don't mix well, so I tried to fill every u joint with only red n tacky, but the slip yoke doesn't have an overpressure purge mechanism, so I'm just gonna have to regularly keep on top of filling it with fresh red n tacky every 5k miles.

The slip yoke being totally empty seems to have the most effect on the clunky driveline and thunk into second / first gear. Every time I grease it, it turns my GX into a whole different luxurious car with imperceptible shifts and more immediate throttle response from a stop. The LX470 had a similar complaint, so looks like some things never change hahaha

 

[maui_ab1]

I'd say it's about as difficult as a diy oil change, though more fiddly if you don't have a way to lift all 4 wheels off the ground. Here's a YouTube diy for the gx460:

It's more or less the same. Somebody please correct me if I'm wrong, but I believe there's 4 zerks for the u joints (one per), but only one slip yoke zerk fitting on the rear driveshaft (now located on the large section of the driveshaft, seemingly different from the gx460 which is on the small section near the u joint). The front slip yoke seems to have a gaiter and no zerk, but I'd like to hear from anybody who's found a front driveshaft zerk.

I use Lucas red n tacky grease, but the manual says any #2 non-moly lithium grease will work. I filled the u joint grease until all the white / grey factory grease was purged, and I pumped like 13 pumps of grease into the slip yoke and it didn't budge an inch - STOP GREASING THE SLIP YOKE IF YOU SEE IT START TO MOVE OR EXTEND. Greases don't mix well, so I tried to fill every u joint with only red n tacky, but the slip yoke doesn't have an overpressure purge mechanism, so I'm just gonna have to regularly keep on top of filling it with fresh red n tacky every 5k miles.

The slip yoke being totally empty seems to have the most effect on the clunky driveline and thunk into second / first gear. Every time I grease it, it turns my GX into a whole different luxurious car with imperceptible shifts and more immediate throttle response from a stop. The LX470 had a similar complaint, so looks like some things never change hahaha

do you think the stealership would do this for us if requested? my 5k is coming up and i'd like them to perform it