Automatic 4wd Selection

[gmyeah]

Just looking for some insight on how the A4WD selection on my 08 sierra 4x4 works. I understand how drive shafts, tranfer cases and differentials work, but was curious on how this choice works when selected. There's 2H, 4H, 4L and this A4WD. So I got thinking about it and here's what I think happens. In this mode, the front and rear drive shafts are joined as in 4WD, but the half shafts aren't connecting to the hub. When the truck (or some sensor) picks up slippage....the hubs lock and you're in 4WD for that moment. Is this right? This would allow you to run it on partially dry roads that have portions of snow for example. You wouldn't have to worry about your tires chirping and beating up your transmission. The selection seem pretty capable, but not completely sure how it works. Am I right? Thanks in advance.

[gmtech4]

well ,you are close ,

 

in auto 4wd the frt diff actuator engages the frt diff,not the hubs..

 

the t case uses a clutch pack with as i remember 8 or 10 fibers and steels,the t case encoder motor ramps up the the fork to near "on " to engage the front output shaft

 

when the Abs system detects wheels slip for the rear wheels the modules have a chat and the t case encoder motor locks that clutch up fast and BAM ......4wd right now

 

awesome system