Nairobi, Oct. 16 -- I have just bought a middle-aged 4WD that has "free-wheeling" hubs on the front axle.What do these special hubs do?Are they essential, or just gimmick?Should I runwith them on "lock" or "free", and when should I change the setting? Clement

Free-wheeling hubs are optional but quite useful - with minor but real benefit to performance, fuel economy and reducing some wear-and-tear.

You should always set them to "lock" whenever you engage 4WD and preferably set them to "free"when you return to 2WD.This is the how and why:

When you are in 2WD, the front prop shaft is disconnected from the gearbox.But it is still connected to the front differential, the front drive shafts, and the front wheels.And those wheels, though no l...