Im just trying to fiqure out my front differential and how it works? I put manual locking hubs on it for starters, but im trying figure out what the purpase of the vacume diaphragm on the differential box. I figure it locks the front cv shaft in, but does it act like a locker or is it still a limited slip differential? And does the transfer case disengage the front drive shaft when its two wheel drive or does still spine?

 

here ya go... this will explain it.....

http://www.ncttora.com/fsm/1990-1995...f/differen.pdf


its an open differential, and yes, the vacuum lines are there to push engage the axles to the diff.

 

You had permanently locked hubs which means that the CV shafts both turn with the wheels. The right side is permanently connected to that side of the differential so although it would seem that it should receive power from the differential, the left side is disconnected until the sleeve engages that side. Therefore the left side output spins freely and since the differential is open, no power is transmitted to the either wheel. When you engage 4wd on the truck, the diaphragm pulls a sleeve and locks the left front axle to the output of the left side of the differential thus resulting in transmission of power to both wheels.