Front Hubs "Lock" or "Auto" ?

[Aleric Meyer]

I had my first 4x4 outing on Sunday. I did Matroosberg, outside of Ceres. The first part is a rocky climb. Had a hairy moment or two! Is it best to leave the hubs in the "Auto" position or "Lock". There was also a lot of snow on top of the mountain.

[Chris Skinner]

In my view it really depends on the situation. In very soft sand, with Auto selected (and probably not optimal pressures), I have sometimes experienced a little difficulty in getting going. This is because, initially only the back wheels are driving the vehicle as the front hubs will only lock after the sart of motion to front or rear, and if the back tyres dig down without forward/rearward movement the front wheels may still be unlocked. I think the same would be the case on a tricky ascent where you need immediate traction from both front and rear from a standing start, so in this case I would prefer to be in LOCK. If teh going is fairly easy and you are in and out of 4wd, I would then have Auto selected. Its really a trade off though - whatever is safest and easiest without becommig a bind.

[dieselfan]

What if you were already in 4x4 low would the hubs not have been locked after driving a bit already?

[Herrie]

As soon as I hit gravel roads, I select 4H. It make thing a lot safer and easier for you and the environment

[Peter Connan]

Dieselfan I am not an expert on auto hubs, but my understanding is that it is "slippage" or relative motion with torque between the side shaft and the wheel that causes them to lock. Therefore if you are in 4l and driving on relatively level and hard ground they may not lock.

In other words what locks them is if the side shaft is turning faster than the wheel, and when the rear wheels have enough traction this is not happening?

[David]

Peter I think that can only happen if you drive in 4x2 as the power will always go the path of least resistance which will turn the sideshaft which will lock the hub. My auto hubs only disengage after I have reversed a meter or two while in 2H

[Peter Connan]

David you have me confused now?

The hub cannot be locked by by motion coming from the wheel side, only by motion coming from the side-shaft. thus the hubs will only lock when the transmission is in 4h or 4l. And since the locking mechanism is a cam that sort of "wedges"the mechanism into place, you probably would have to reverse a little bit to unlock it again.

Personally I beleive it is better for the bearings etc. to be turning, particularly on corrugated roads. I lock my (manual) hubs when I leave the tar if I think there is any chance that I will need 4x4, and only unlock them again when I get back on the tar for the last time on the trip.

[David]

... Therefore if you are in 4l and driving on relatively level and hard ground they may not lock...

Hi Peter I agree with everything you said except the above statement as I feel the sideshaft will in any case turn and cause the hub to lock no matter what the terrain as long as you are in 4x4 (power to the front wheels). If they don't lock then there are something wrong with the hub or your sideshaft is busted. They hubs should lock in either direction - forward or backward - as long as a force is supplied

[Stefan]

on Auto, mine engages almost as soon as the stick is moved from 2H to 4H, and disengages within a meter or 2. I always depress the clutch when moving the lever - maybe the re-application of power causes the locking mechanism to activate?

[Peter Connan]

David looking at the manual, some of the parts of the mechanism are mounted in the hub casing, which turns with the wheel, and the rest of the parts are mounted on the side shaft. None of the components making up the mechanism are connected to the axle tube.

Thus the mechanism can only detect differences in speed between the wheel and the sideshaft, but can only be activated by torque from the half-shaft, with a difference in speed between the wheel and the half shaft. Thus when there is no loss of traction on the rear wheels, there will be nothing to tell the hub that 4wd has been selected?