We've owned our 2005 4Runner since new, sounds normal to me. On steep inclines, after being at a dead stop with foot applied to brake pedal, as I move my foot from brake to accelerator pedal it will make the rapid clicking sound. This is the brakes applying (it's using ABS system to apply brakes, same sound when you slam on the brakes and ABS kicks in). If it's for more than about 2 seconds, it'll beep too. You'll notice the traction control light come on in the dash at that point too. Once you start accelerating forward, the system is back to normal and traction control light will be off. If you hear the noises and your 4Runner continues to roll backwards, you might have a problem. Test that without anyone behind you.
Thank you. It was definitely for less than 2 seconds.
