I have my front frame up on stands, and I noticed today that my front diff input shaft flange did not spin with either wheel turning. (Transmission and engine are both out of vehicle).
Turn flange by hand, neither left or right wheel would spin. I thought that is odd.

So set about and pulled the disconnect. It was over towards the driver wheel. Got handy-dandy hand vacuum pump, and 10 or 15 inches of vacuum pull the fork easily either direction.

Reached in and moved the collar towards the pass' side. engaged both axles, turn either wheel and the flange turns. Un-engaged and maybe the right wheel might turn, maybe sometimes not. Usually neither would spin. Can not remembere now, but -think- either wheel would always spin flange when collar is engaged.

Is this correct operation?

I have a printed FSM, and didn't see anything about operation. Don't be shy telling me I missed it. My ex will tell you I can't find my butt with both hands and a flashlight. (Testing the actuator - but pretty much as I had done.) And it holds a vacuum for at least a few minutes, meaning the hoses that connect at the VSVs don't leak down. I got to wondering if my front would engage at all once up and running. (Target date spring 2035 !!)

95 4runner body/frame/axles. (originally automatic transmission). NOT free wheel locking hubs either.

 

Perfectly normal operation. The ADD (Automatic differential disconnect) disconnects the left CV shaft from the left stub shaft inside the differential. With that done, the left wheel can't turn any part of the diff. The right wheel will spin the spider gears in the diff, and the left stub shaft inside the diff winds up spinning backwards (but you can't see that.) The ring and pinion have more friction resistance, so they just sit stationary. If you spin the pinion flange, the spider gears again spin just the left stub shaft, because it's the lightest and lowest friction piece of the diff.

 

Thank you!