The oil pan.
in the usa this cover is called the oil pan. in other countries it is called the sump pan
The pan (usually black in color) on the bottom of the transmission serves as a reservoir for transmission fluid. Keep in mind that that it holds only about half of the total transmission capacity.
The bladder serves as a temporary reservoir for urine before it is eliminated from the body.
the bone marrow
On the bottom of the engine and on passenger side back if memory serves.
Adipose serves as the body's primary energy reservoir.
If the 2006 Armada is the same as the 2005, there is not a separate reservoir for the rear. One reservoir serves both front and rear. It is under the hood, on the drivers side on the front corner. When you add washer fluid, you actually add it directly to the reservoir. The pump, located on the back of the reservoir, near the bottom, will have two exit nozzles on it, one leads to the front windshield, one to the back.
The same reservoir that serves front wipers serves the rear window. If the rear sprayhead is not working then it may be blocked or the line to the engine compartment may be pinched, or have come disconnected.
the stomach
the oil drain plug is located at the bottom of the sump under the engine. If memory serves you will need a hex bit to remove it.
Your car may or may not have a trans dipstick, but on my '96, it's located on the driver's side of the engine, toward the rear of the engine. If memory serves, it's more or less, under the brake fluid reservoir. FriPilot
It is noise .