i have AVM hubs and they work great. all you have to do is go to each when and lock it, then put it in 4x4 and she should work. then for fuel economy u can unlock it and the front wheels will just free wheel instead of spinning the from cv
shafts. as for why yours stopped working who knows, could be vacuum leak, hubs could be stuck in the unlocked position. manual hubs are way more reliable.
1999 Ford Ranger Ext Cab XLT 3.0 Auto 4X4 4.10 non L/S
mods: airbox mod, 6000k HIDs, AVM manual locking hubs
coming soon: tint, tri-fold tonneau cover, lift, rims and tires!