The 3000 rpm Rumble

This particularly frustrating noise is only generated by the RS200 (3S-GE) 6 speed manual Altezza.  When you take your foot of the accelerator and let the car decelerate down through 3000 rpm a deep rumble reverberates through the cabin.

Listen for yourself:

Raw Rumble (104 kb, 6 seconds)

Filtered to remove high frequencies (104 kb, 6 seconds)

You'll need to listen to this through a good sound system - the rumble is down below 200 Hz, well out of reach for most computer squawk boxes.  YOU WILL NOT HEAR THE RUMBLE WITHOUT GOOD SPEAKERS!  It's not the best capture of the sound, but hopefully it gives you an idea of what I'm on about here.  The rumble starts at about the 3 second mark, when I take my foot off the accelerator.  I intend to record some better examples when I get more time.

As yet I am not aware of the true source of the noise, let alone the cure.  So, if any of what I present here sparks some ideas in you, PLEASE let me know (use the link bottom-right)

Personal Experience

The rumble is very pronounced on mine (standard factory clutch and dual mass flywheel). Or maybe I'm just very attuned to it!? It’s not just a noise, but also a definite vibration – you can ‘feel’ it coming up through the body of the car.  Very noticeable on smooth seal. It happens when lightly engine breaking down through 3000 rpm on flat road, slight inclines and declines. Have noticed it in gears 3 through 6. The rumble stops as soon as the accelerator or clutch is pressed.  May be more pronounced if you play on the throttle - accelerating from 2500 to just over 3000 and then let it come down again, rather than letting it come all the way down from 4000 or above.

I’m pretty certain it’s not an exhaust thing - rattling heat shields and exhaust joints tend to be more of a buzzy sound and certainly not a low frequency vibration like this, nor is it the drone of an exhaust.  Induction noise was a popular theory for a while (I’ll explain more later) but after some trials I’m currently less convinced. 

Current speculation is that it’s clutch, flywheel or diff related.

I have eliminated drive shaft as the cause.  Mine had notchy universal joints and was looking promising as a cause.  However, it has been replaced and the rumble remains as strong as ever.

I can’t seem to get the rumble when the car is cold.  I haven’t managed to confirm whether it’s engine cold or driveline cold that’s not generating the noise.  Regardless, after 10 minutes of driving the rumble is there with a vengeance.

Information from Others

Thread at NZ/Aust. Altezza Forums
Thread at Lexus Owners Club UK Forums
Rumble Gone Thread

Update - Rumble Gone! (19 Nov 2005)

Fitted new genuine Toyota:
 With the rumble gone there's a lot of other little rattles that were happening on the overrun that have also shut up. For example my accelerator pedal had a rattle (that I was getting around to fixing...) but has gone completely. Just goes to show how much of a vibration the rumble used to send through the car.

The gears now engage a lot more smoothly, there's no shudder on cold take-offs and the stick feels less notchy between gears.

The 'thud' when you push through from 1st to 2nd reasonably quickly still exists, as does the front shaft gear chatter in neutral. But you can hardly expect a clutch and flywheel change to fix those 'characteristics'!

Playing with the old dual mass when it was out apparently you could feel that the 'springiness' in one direction was not there, so the dampening effect wouldn't have been working. The question is was the worn dual mass the cause of the rumble, or was it just unable to dampen the rumble? Toyota must be using dual mass for a reason, and the reason is most likely to dampen such vibrations.

Anyway, no rumble, happy happy joy joy...
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