Assuming stock Ford "Auto-Hubs"?
Too much grease will prevent them from locking, very light coat on the locking parts are enough, i.e. don't pack them with grease like you would with regular bearing cap.
Front axle is an OPEN differential, so only one axle will get power, the one that is easiest to spin, so shortest axle, if you stop that axle/wheel from spinning the other axle should start to spin because it is now the easiest to spin.
If you spin the front drive shaft in the "forward" direction both hubs should lock.
If you spin a wheel in the "backward" direction that hub should unlock.
Rear axle on most Ranger 4x4s is L/S, Limited Slip, and both axles get power
When you engage 4WD in the transfer case the front drive shaft will start to turn when you move and that engages the Auto-Hubs, when you put transfer case in 2WD the front drive shaft will continue to turn because hubs are locked, but front wheels won't be powered by the engine.
To unlock the hubs you need to back up a few feet, sometimes 50+feet, while in 2WD.
You will hear a "clicking" noise if an Auto-Hub is not fully engaged or dis-engaged.
OPEN differentials are less expensive to build and that is what 95% of the cars and trucks made have used and still use, and that is why when you get stuck only one wheel spins, lol, the easiest wheel to turn gets 100% of the power.
L/S, Posi-traction, Trac-Lok, ect..............have clutch discs in the differential, if one axle starts to spin faster than the other the clutch discs are forced together and equalize the power going to the slower turning axle.
This presents a problem since vehicles do have to go around corners, outside wheel has to spin faster than inside wheel when cornering, so these clutch discs need to slip when speed difference isn't that much, usually there is an additive needed in the differential oil to aid in this "limited slipping".
Last edited by RonD; 07-04-2015 at 10:01 AM.