Why does the Rear windshield wiper goes down below window on your 99 Chevy venture?

The rear wiper on a 1999 Chevy Venture (and many other vehicles) doesn't actually go *below* the window in the sense of physically extending past the bottom edge. What you're likely seeing is the wiper arm continuing downward past the bottom edge of the window glass. This is by design for a couple of reasons:

* Coverage: The arm extending slightly below allows the wiper blade to fully clear the lower portion of the rear window, achieving better coverage and preventing a streak at the bottom. The blade's arc is slightly larger than the window itself.

* Mechanism: The motor and linkage mechanism for the wiper are housed within the vehicle's bodywork. To provide the necessary arc of movement, the wiper arm needs to extend beyond the glass. If the arm stopped exactly at the window's edge, it would likely limit the effective cleaning area.

In short, it's not a malfunction; it's intentional design to improve wiper effectiveness.