2000lexislx470 rumbling type noise that seems to be coming from dash area behind speedometer

Sounds like a half shaft. Reach around behind each wheel and see if there is play in the shaft that leads from the wheel to the transmission. There should be no play. Other possibility is a bearing hub. Jack up car, grab the tire at 9 and 3 o'clock. Shake wheel if there is movement not from the tie rod then it is the bearing hub.

Spin that wheel by hand as fast as you can. If you can hear the noise coming from right behind the tire it's probably a wheel bearing.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

I have the exact same problem on my 08 starts at about 65mph and is really bad above 80 goes away at 95 or so. I have determined that it is not a motor. I think it is a wire that is vibrating against the dash pad. I am going to take my center console out and lay the radio and climate controls to the side and drive the car to see which wire it is. I tried removing the console and securing all the visible wires last night. but the problem is still there so I may have missed it. Driving and seeing behind that area and looking for the culprit is the only sure fire way for me to positivley Id it. I will let you know what I find out. you please do the same. [email protected]

You must first disconnect the battery cables.
Then you begin work from the driver's side with a 4-corners screwdriver, palm-type and 6-inch long.
Remove the screws holding the speedometer.
Open the doors and locate the screws holding the dash to side of frame.
In the gearbox areas are screws holding the center console panels to frame, remove as well.
Use flat-end screwdrivers to remove the snap-fit plastic panels.
Open the glove compartment and remove its screws holding it up. Then lift it out.
Continue to locate/remove the screws holding the dash to frame.
Pull out the radio knob, and unscrew the stereo from the sides.
Reach behind stereo to unplug its wires, and disconnect antenna cable.
Unscrew the speedometer screws, and unplug their wires from behind.
Lightly shake the dash and see which screws remain. Remove as necessary.
Reverse this procedure to install back the dash.
I'd recommend getting a reapair manual such as Hanyes to due to the complexity of arrangements of parts.

there is a mode controller/actuator in the passenger side area(behing glove box) that will make clicking and rattling noise when failed but I cant say it makes a "horrible" rattle but it is quite audible clicking and clearly is a noise coming from inside the left dash area

that clicking noise is coming from a one of the blend door actuators under the dash. not too bad to change. while it's clicking, feel behind the dash in the area you hear it, to get an idea where it is. most likely your only problem. good luck with it ....

Probably the speedometer cable needs to be removed and lubricated.

Check the water coolant level because some of the hot water goes into the heater radiator behind the dash. Seems you have air in the system.

heated water goes to your heater core under your dash..though you shouldnt be hearing it usually..be sure water level is up at radiator overflow reservoir and pay attention in cabin of any sweet smell of coolant indicating a failing /leaking heater core....look for damp carpet on passenger front area if suspicious

it sounds as though its coming from your computer which is behind the glove compartment.