Been wondering that lately with my '94 F150 4x4. Has it's original auto hubs, and they work, but lately using them and spinning around in 4x4, sometimes the whole truck will start very very violently shaking,, feels like the front wheels are locking/unlocking very quickly, it does it very badly in reverse.


Is this signs of failing hubs?

Truck has 93k miles on it.

 

The auto hubs usually fail by refusing to lock in reliably. That said, I've read people having them not engage fully causing grinding noise & vibration...
Whey you change direction (forward to reverse & back again), they un-lock & lock again, so if it's slick and you start spinning before they lock in it can cause quite an impact...

 

No, they usually shake and vibrate long after they're locked in.

 

These auto-locking hubs are designed to engage when torque is applied via the axle shaft. They are to disengage when input torque is no longer applied and the direction of rotation is reversed for a given [short] distance. Failure can occur when one (or more) of the engagement cogs breaks or if the grease is lacking or dirty thus preventing the cam or disc to rotate into the engaged position. Unfortunately both hubs usually do not fail at the same time leading to the possibility of ruining your differential (by way of one hub being engaged while the other is not) if you do not catch the problem in time. Best answer? Replace those so-called "auto" hubs with manuals. The only better time to do so than today... was yesterday!

dn.