[jdmccright]

You still need an aftermarket brake controller. The Avs didn't offer an integrated controller until 2009 models. Some GM HD trucks offered it starting in 2007, but read some of those have issues. My guess is that somehow your trailer brakes are reading the "STOP" lamp voltage as the signal which is either on or off...no modulation.

The slider you refer to is the "gain" input that adjusts the electric brake voltage signal according to the controller's inertial sensor and brake input. More gain means that the trailer brakes are applied more firmly in proportion to the controller's sensors. Some controllers have this slider work opposite to logic...moving it to the left INCREASES gain instead of to the right, etc. This is not to be confused (as you may know) with the manual brake slider that lets you apply the trailer brakes separately to correct any swaying or to help with descents down steeper grades.

Finally, some controllers have a delay setting to when the trailer brakes are applied once the controller senses that the truck brakes are being applied. Hope this helps!