#3 Checkball (Intermediate Band Apply)
WARNING: This page is about a different car, the 2008 Pontiac G5 and 2008 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.
Intermediate band fluid pressure seats the #3 checkball and is forced through the #8 orifice. This orifice helps to control the intermediate band apply.