First time posting, love this forum. I have a 2002 SR5 4Runner with 4WD. I am second owner and have it for 8yrs. Love this truck! All maintenance is up to date and in excellent condition given it is 14yrs old and has 170,000mi. I use it as my daily driver and noticed yesterday a loud metal sounding vibration when I place it in gear with the brake pedal depressed. When it is moving or in Park/neutral, no loud sound. I had my brother place it in gear while looking underneath and it seems to be emanating from the rear driveshaft next to muffler. Can't tell if it's the exhaust or possible U-joint for driveshaft. It drives fine and does not emit metal sound when driving. If anyone has any idea as to what it is, I would appreciate. Taking it to my mechanic on Tues.