I have a 99 ranger 4x4 4l with manual locking hubs , 4x4 seems to only work when the hubs are locked . Is this normal . Just purchased the vehicle dont know much about these

 

If they're unlocked, the wheel/hub assembly spins independently of the axle, so power from the engine cannot be applied.

 

Welcome to the forum

Yes, +1 to above

Your 1999 Ranger came with Automatic PVH(Pulse Vacuum Hubs) from the factory, these were used on Rangers from 1998 to 2000, but they started to have problems almost immediately, failed to Lock or unLock.

So many changed these years to Rugged Ridge/AVM Manual locking/unlocking hubs so they could have reliable 4WD
By 2001 Ford switched all Rangers over to full time Locked front hubs, no unLock, Ford called it Live Axle.

During winter months people with 4x4's will leave manual hubs Locked all the time, doesn't hurt anything(if you had a 2001 or up Ranger you would have no choice, front is always locked).
Then they shift into 4WD when needed, and back to 2WD when they want

You should be in 2WD on dry roads and if you will be driving above 50MPH
4WD is best suited for slower speeds(under 50MPH) and marginal traction conditions
State of the hubs, locked or unlocked, doesn't matter in above, just transfer case selection matters

In summer people will unlock the hubs, you pickup about .3MPG with hubs unlocked, not much but not nothing either, lol.


And just a heads up about 4WD, it doesn't help if there is ICE, you WILL fly of the road if you hit ICE, and this is why you see mostly 4WD vehicles in the ditches when roads are icy, people think they will have better traction with 4WD, and you do BUT...........not if all 4 wheels are on ICE

4WD's main benefit in a pickup truck is that you have the weight of the engine on one of the driving axles, like Front Wheel Drive cars which do better in low traction conditions than Rear Wheel drive cars/trucks.
And the laws of physics, it is easier to PULL a load than to PUSH a load, front wheel drive/4WD PULLS the load