Thump when braking/slowing (1 Viewer)

[mateo4012]

Hi, I have a new GX500 Premium (less than 200 miles on it) and have a weird issue:

• When slowing to very low speeds from normal driving, there is a single deep thump (sounds exactly like bass from a speaker)
• This thump typically happens at 12-14mph when slowing down, and is pretty consistent (though it doesn't happen 100% of the time); it's not super-loud, but is noticeable.

I'm thinking it has something to do with the transmission or drive train, but wonder if this is a known issue or anyone has thoughts on what it would be. Thanks!

 

[incognito.gx]

Hi, I have a new GX500 Premium (less than 200 miles on it) and have a weird issue:

• When slowing to very low speeds from normal driving, there is a single deep thump (sounds exactly like bass from a speaker)
• This thump typically happens at 12-14mph when slowing down, and is pretty consistent (though it doesn't happen 100% of the time); it's not super-loud, but is noticeable.

I'm thinking it has something to do with the transmission or drive train, but wonder if this is a known issue or anyone has thoughts on what it would be. Thanks!

Known issue. Have dealer rest transmission memory.

 

[mateo4012]

Known issue. Have dealer rest transmission memory.

Thank you!

 

[GX550ooh]

Known issue. Have dealer rest transmission memory.

Do you happen to know the code for this fix? I’ve mentioned the issue to my dealer here in Western MA, told him that I’ve seen several forum members mention a transmission memory reset and the service tech told me it’s a known issue but that Lexus are still working on a fix “to appease the customer”.

 

[KatGX]

I was told the same. It’s caused, or so I’m told, by the brain and the transmission predicting the way you drive. More prevalent when there are multiple drivers.
My “kerr chunk” seems to have mellowed a lot since I got around 20000mi

 

[Laxal550OT+]

Definitely a known issue and you should report to Lexus corporate. I did and surprisingly Lexus corp actually contacted me and my dealer to “document” the concern and said they would reach out when a solution is identified. I expressed my dissatisfaction and disappointment with such an expensive car. Shared how I am reminded of the problem literally every time I drive the car and slow down to a stop. Very frustrating!

 

[GMan93]

Noticed same thing on my 2025 during first 500 miles. It's since gotten a bit better I feel and doesn't happen all the time only if I break hard it seems. Either it's kind of learned my driving style or I guess i've learned to feather the brake to get it to smoothly stop. I definitely know what you're talking about though during that 12-14mph slow down 2-1 shift. Like a "dum" sound and you feel it a little more. Hopefully they come out with something soon. Haven't brought it up but will on my 1st service.

 

[mateo4012]

I just had the software fix applied to the transmission, but the sound is still there--pretty frustrating

 

[GMan93]

Sound still there for me too. Low bass "boom" when coasting or braking at 12mph. Never experienced anything like it in any car i've ever driven/owned.

 

[BackRdRnr]

Remember it is a 10 speed that upshifts out of first gear at 5 or 6 MPH at slow speeds. The downshift you feel is a difficult one because of the low gearing for off road capability. This truck was engineered to provide you off road use so I give it a break on some issues. 2 cents.

 

[GMan93]

Remember it is a 10 speed that upshifts out of first gear at 5 or 6 MPH at slow speeds. The downshift you feel is a difficult one because of the low gearing for off road capability. This truck was engineered to provide you off road use so I give it a break on some issues. 2 cents.

It doesn't always do it is the weird part. And always the same exact mph it's actually the 3-2 shift (12mph) and sound. Only downshift never on the upshift. I saw some say greasing the slip yoke and u-joints helped some with rougher shifting, not sure if it is the cause of this issue...may try when take back to dealer for next service unless anyone else can confirm the existence of this and if they've found an actual solution.

 

[BackRdRnr]

It doesn't always do it is the weird part. And always the same exact mph it's actually the 3-2 shift (12mph) and sound. Only downshift never on the upshift. I saw some say greasing the slip yoke and u-joints helped some with rougher shifting, not sure if it is the cause of this issue...may try when take back to dealer for next service unless anyone else can confirm the existence of this and if they've found an actual solution.

IMO it is the tranny and the computer deciding it is time to shift. Speed that you are decelerating also factors in to the shift. I suppose it does not always happen because of the speed/ slower is softer shift/more time for the shift to occur/less pressure on the drivetrain as it engages the next gear. Only the service folks will know for sure. 2 cents.

 

[cmfhsu]

Sound still there for me too. Low bass "boom" when coasting or braking at 12mph. Never experienced anything like it in any car i've ever driven/owned.

Highly suggest lubricating your driveshaft u-joints and slip yoke - this was the solution to my thumping & clunky dump-truck-ness, even after applying the software calibration fix.

Anyone know if the GX550 Has Grease-able U-Joints

Just wondering if greasing the drive shaft u-joints are part of the 550's regular maintenance or if they are "lifetime" u-joints. I will eventually crawl under there and check for zerks during my first oil change, but I'm only at 200 miles.

www.lexusgxforum.com

It looks like the GX550, like the LX470 before it, requires a lot of grease to quell thumps and drivetrain lash - and the car comes with almost none when it's delivered. You can either DIY it (not super hard, but a little time consuming), or ask a shop to do it for you. Any local independent shop will do it no problem - some Lexus dealers might give you some grief when you ask because customers rarely request that service.

 

[GMan93]

Highly suggest lubricating your driveshaft u-joints and slip yoke - this was the solution to my thumping & clunky dump-truck-ness, even after applying the software calibration fix.

Anyone know if the GX550 Has Grease-able U-Joints

Just wondering if greasing the drive shaft u-joints are part of the 550's regular maintenance or if they are "lifetime" u-joints. I will eventually crawl under there and check for zerks during my first oil change, but I'm only at 200 miles.

www.lexusgxforum.com

It looks like the GX550, like the LX470 before it, requires a lot of grease to quell thumps and drivetrain lash - and the car comes with almost none when it's delivered. You can either DIY it (not super hard, but a little time consuming), or ask a shop to do it for you. Any local independent shop will do it no problem - some Lexus dealers might give you some grief when you ask because customers rarely request that service.

So took in for 5k service. Was able to drive with tech and have him experience the issue and he did note what I was experiencing is real. They had a couple other GXs on site to compare to. From just talking to him and telling him about possibly greasing the slip yoke he said he'd throw some more grease on it and also disable the fake engine noise. They had some other GXs to compare against and after he did they said the others seemed to do something similar. Not sure if they actually greased anything as the report just said that it was deemed a "normal" thing that the other GXs also did at this time and didn't note anything about grease when I went to pick it up later(service manager couldn't confirm anything was done other than what was in the write up), but it is driving a good deal better now so think they may have. Either that or just doing an oil change and topping up fluids did something...lol. Either way happy for now and will probably have things greased either by my independent mechanic or the dealer again at 10k.

 

[BackRdRnr]

thanks for the tech info on the grease fittings..........I assumed they were sealed joints these days! I will be looking into those needing attention. Happy ThanGXgiving!

 

[GMan93]

Finally found the solution to this for anyone wondering.....You need to disable the ANC (Active noise canceling) and Fake Engine sounds in the vehicle. I'm guessing for some reason the car tries to cancel out the engine downshift noise or pumps in extra noise right around that 12-14mph downshift and it creates this annoying "bass boom" sound which when disabled it doesn't do and it's 1000x better. I indirectly suspected this eventually as when I had the moonroof open or windows down in the car the sound would stop. Put 2 + 2 together and realized it's probably something to do with the noise canceling/fake engine crap and had it disabled. Dealt with this annoying issue for a good part of a year and happy to have finally found the solution for it. (Came to find out the dealer actually in fact did NOT disable to the fake engine noise when they had said they did and the ANC was also on). When I confirmed they were disabled now the issue is gone.

 

[mateo4012]

Finally found the solution to this for anyone wondering.....You need to disable the ANC (Active noise canceling) and Fake Engine sounds in the vehicle. I'm guessing for some reason the car tries to cancel out the engine downshift noise or pumps in extra noise right around that 12-14mph downshift and it creates this annoying "bass boom" sound which when disabled it doesn't do and it's 1000x better. I indirectly suspected this eventually as when I had the moonroof open or windows down in the car the sound would stop. Put 2 + 2 together and realized it's probably something to do with the noise canceling/fake engine crap and had it disabled. Dealt with this annoying issue for a good part of a year and happy to have finally found the solution for it. (Came to find out the dealer actually in fact did NOT disable to the fake engine noise when they had said they did and the ANC was also on). When I confirmed they were disabled now the issue is gone.

That's incredible, thanks for sharing the solution! How did you disable the fake engine noise and ANC? Does the dealer have to do this?

 

[GMan93]

That's incredible, thanks for sharing the solution! How did you disable the fake engine noise and ANC? Does the dealer have to do this?

Dealer can do it or if you have an OBD device you can do it yourself. You can order one off amazon for like $30-40 I think.