No pulsation. It seems to start at 25-30 but you can hear it slower upon decel. I do not believe it is rotor or caliper related. Brakes were good last time I had the wheels off and the pedal doesn't pulse. Nothing in the steering either.

 

Well when i said pulsation... what i was getting at is the audio/sound your hearing have a oscillation or pulsation?

 

No, it is a pretty constant growl.

 

I think you'll find (eventually) that the growl/roaring noise is naturally coming internally from the AWD transfer case and transmitted via some mounting/support bushing or component directly or indirectly associated with the transfer case which has become either hardened or deteriorated - allowing the noise to be transmitted to the frame instead of isolating the noise from the frame to reduce the noise from being heard inside the cabin. That said, I doubt there is anything wrong with the internals of the transfer case. I also rather doubt a worn or defective axle/wheel bearing is causing the growl or roaring noise.

 

Until I crawl up under it, I'm going to go with this assumption as well. It isn't louder with the windows down at any corner and appears to be emanating from the middle of the car when sitting in either front seat. Best I remember, the rear wheel bearing was pretty loud and pretty obvious in turns.

I may stick my cheapo GoPro knock-off under there to see if anything can be narrowed down.

 

hmm...uh-huh, yeah, yeah

 

When you hear the noise next time throw it in Neutral, coast and do things like hit the Brakes and listen in Neutral and see if you hear the same noise. Tell us what happened then?

 

Already did that. No change. It is 100% speed related. Not engine or torque converter.

 

That would indicate the noise is coming from the area beginning with the transfer case, including the drive shaft and ending with the differential. The drive shaft would have to be making contact with something (rubbing) to make a noise, otherwise it would be spinning in an out-of-balance (unbalanced) condition which would cause a noticeable vibration/shimmy (which it's not). The differential having a bad bearing that makes the roar noise you're hearing is unlikely in my opinion.

As previously mentioned, I think the natural noise generated by the AWD transfer case is being transmitted to the car's frame via a failed (hardened or deteriorated) mounting bushing, its purpose being to isolate the transfer case noise from the frame.

 

Here is an audio recording where my phone was laying on top of the hump for the transfer case. You can hear the engine and when I let off, the roar is more prominent. You can barely hear me say 30MPH and 40MPH since this is basically under my knee. I slow down and then accelerate again.

Hopefully, this works. It is shared from my Google Drive.

Audio of Roar

 

Listening very carefully, it sounds similar to what a manual transmission with a degree of gear drive lash (intentional play, slop or clearance between gear sets) sounds like when going from an unloaded (i.e coasting) condition to a loaded (i.e. under a degree of acceleration) condition. All pretty typical... I'd look for a failed bushing that (when undamaged) is intended to absorb or prevent that gear drive noise from being transmitted to the frame and inside the cabin.

 

Yes, my other car has a Muncie M22 so I am very aware of those sounds. They are more of a whine due to straighter cut gears. It also is per gear and not completely MPH based.

I will get it on the lift this week and check it out hopefully.

 

 

I took a long, winding drive to my dad's farm yesterday and when I stopped, I checked all the bearings with my infrared thermometer. All the front and rear bearings were within 2-3° of each other. I checked as close to the wheel/rotor mating surface as I could and also at a lug nut just to see what it was. They were all around 117-120° so that would rule out a bearing.

Further up the rotor where the pads run, they were all well over 140° but still within a nominal range so no calipers sticking.

I'm procrastinating and dreaming up other projects to avoid putting it on the lift. I'm actually waiting for a buddy to drop by so I can do it without involving my wife. She tends to abhor anything car related.

 

Sometimes a Lexus Whine is the Front Transmission pump going. Seems you don't think its the trans at all. Listening to the Vid also does not sound like the Lexus trans pump whine either. The Trans pump can throw you off noise wise and sometimes does not change with RPM or speed once it starts Whining. That some more roaring than whine noise?

I don't know if you have already done this, but I would drain and refill the diff and front transfer case fluid also. Listening to the recording it sounds like 100% drivetrain, front and/or transfer case, rear diff??? I did notice a little shake on the dash? Is that the car or just the recording device shaking? My guess is front transfer diff, or rear diff. This is strange, cause it also had the drive axel wheel bearing type noise also. ppl have already been replacing wheel bearing on these 4th Gen GS's. I think to nail it down you may have to lift the car, let someone put in gear carefully and accelerate to listen and pin point where its coming from.