Greetings folks,

There's a pulsing rumble from under the car (definitely in / around the transmission) from perhaps 5 through 15mph and again 45-55mph. There's also a distinct bad-bearing howl coming from the same area under the car when it is idling in drive. Putting the car in neutral makes the howl go almost completely away. Neither of these behaviors changes based on engine temp or fluid (the fluid is now fresh). Finally, the transmission behaves a little odd from take-off, although it's just kind of 'random', sometimes it shifts a little rough 1-2, sometimes I have a little problem with hunting gears between 2-3 and 3-4. All very random and very mild.

I have a rebuilt torque converter order ready to go but it just seems like it could be a bad bearing or even clogged transmission filter. Previously on this forum "bad torque converter" was the immediate reaction and it seems to at least partially fit the symptoms, but there isn't any lack of power, poor fuel economy, stalling. Since the "howl" is only at idle that goes away as soon as the engine is spinning over 1k rpms, I'm somewhat suspicious that I have a bad bearing, rather than a bad TC... or maybe both.

Any thoughts?

Thanks all!

 

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Anyone have any thoughts about that bad-bearing howl at idle? Hoping for someone who has heard it in their car before!

Thanks!

 

73k? sure its not the rear end? check the filter... how was the fluid when you changed iit? , what did you put in there? it takes t-4 toyota only fluid. weird it would help if i could hear the sound although im not an expert and im not sure if i could help. good luck

 

Hi Will, I am sure it's not the rear end. The bad-bearing whine/howl only occurs when the car is still. The diff never slips even under full load, makes no noise and seems to be in perfect shape.

The transmission mount is also, at least visually, in perfect, virtually like-new condition.

I flushed the ATF but this had no impact on either the bad-bearing howl noise when sitting idling, nor on the rumble at 45-55mph.

I already ordered a rebuilt TC but I'm hesitant to dive in to this if it might be as simple as a clogged filter. It looks like it's going to be pretty involved to try and drop the transmission out in my driveway.

 

Just some advise, if you do end up dropping the tranny out make sure you change the rear main seal and the front seal in the tranny. And check the EGR pipe for cracks, it's a common problem and easier to get to with tranny out, from what I've read here.

 

Well, I have some GOOD news here. My continued problems are due to my own laziness, not a failing torque converter. I had flushed the transmission fluid and replaced w/ Valvoline high-mileage, which only temporarily reduced some of the noise; it quickly came back, and I'd even say, was worse than ever.

Yesterday I decided to drop the pan, clean out the pan & magnets, replace the filter - and sure enough, the pan was coated in metal sludge, the magnets were covered, the filter screen was clogged.

Wiping everything clean and installing a new filter has caused 90% of the sound to go away - both at idle, and the rumble at speed. Apparently this was almost entirely due to fluid starvation, not a failing torque converter. The car is working spectacularly now - the way a Lexus should - extremely quiet and smooth.

So, happier days ahead with my new Lexus!

 

I will advice you to drain All Valvoline fluid and use Toyota ATF-IV. our transmission is sensitive to fluids.

 

Thanks, I spent a fair amount of time scouring the history here, the interweb for other info about the A650E, and I believe even started a thread on the topic of transmission fluid. The conclusion was that folks had used other oils than Toyota T-IV successfully. The Valvoline high-mileage also says it meets the Toyota T-IV spec. Cheap Dex/Merc oil is $1.50 per quart and I paid $5.50 for the Valvoline, so it's not the cheapest option out there. But it does seem to be working splendidly in the gear box.

I just swapped out transmission fluid in one of the Mercedes with fluid that costs no less than $25 per quart. I could not find any reliable information indicating that any aftermarket option was viable for that transmission (designated 722.6), although the Mobil 1 Full Synthetic may have been recently certified for similar M-B transmissions.

I'll definitely report back after I have one or two thousand miles on this oil to see if it still seems to be working well; I suspect it will be fine.

 

Nice job. Feels good to have Kiro running back the way it should doesn't it!

 

thanks for that info because mine is doing the same thing and also my egr is cracked so it makes a horrendous noise. so while im under there i will do so and well hopefully i yield the same results as yourself.

 

Hello everyone,

I am a new member with 98' LS 400.
Bought used at 25k on it and have enjoyed the car without major issue for many years.

Recently it developed a disturbing humming noise at starting and idle.
It gets louder when air cond is on.
The car performance is still OK except the annoyed humming noise at stop sign.

Have the transmission fluid replaced but the noise is still there.

Checked with several mechanics and was told the car needs a used transmission.
Cost varies from $2000 to $1600 and $1100.

Other said it only needs a rebuilt torque converter ($200 part and $450 labor).

Wonder which way should I proceed?

Appreciate your input.

 

Oh I forgot......my LS400 current mileage is 250k.....
The body and paint and interior are still in good shape.
I would like to keep it for few more years.

 

How is the shifting? With the A/C on I begin to suspect that the humming noise is something that is being driven by the serpentine belt. Has the timing belt, water pump and idlers been done at the 200K mark? Any signs of leaking power steering fluid?

 

timing belt, water pump were replaced at 180k (at each 90k intervals)