How exactly does the blazer's autotrac 4wd system work? Im use to the locking hubs. Also should my front drive shaft be spinning when 4wd is not engaged?

 

The 4wd works by engaging the transfer case in the proper range and engaging the front axle with a vacuum actuator. On the front axle the left driveshaft is always connected to the differential and the right driveshaft is engaged/disengaged, so your front driveshaft is always turning when you're moving. When in Auto the front axle is engaged and the transfer case is in 2WD mode, if it senses a speed difference between the front and rear axle it will briefly shift the transfer case in 4WD mode (up to several seconds if it still senses slippage). There's a clutch pack so it doesn't grind the transfer case in Auto mode. When you change the fluid you use the factory GM Autotrack fluid, there is no substitute.

 

well iiiiiii learned something today!