We loved our auto hubs right up to the point where they blew up our front ring&pinion set.
They always engaged when we wanted them to, they lasted great, never broke them. Loved them in the winter.
The only problem was when climbing up a steep hill in 4wd high, we bogged down and started to roll backwards.
I hit the brakes, engaged 4wd low. I then proceeded to hit the gas and attempted to go forward and BAMB!!! No more 4wd.
I found out that the auto hubs became unlocked when I rolled backwards (easy to do with a stick) and then they abruptly locked when the drive train was already moving forward in the rear and it knocked a couple of teeth off of the pinion gear.
Those teeth then got shoved into the housing by the ring gear, and destroyed the housing too.
That was the last time I used auto hubs.
Manuals or flanges after this.
~Nate