Problem with 4x4 Auto mode

[ExSport]

I noticed something unsettling this weekend when backing up my driveway. My driveway is short, straight, moderately inclined, and at the time was a bit slippery with snow on top and ice underneath.

I had the 4x4 system set to "AUTO" mode as normal. I started to back slowly up the driveway, and my Explorer started making an awful banging noise, maybe 4 or 5 times, seemingly as it went in and out of 4WD as the wheels were slipping.

I read in some of the other threads about how the ControlTrac system works, and that there can be a slight "thud" when power is transferred to the front. But I believe I experienced something more serious than that. I also read how the transfer of torque is progressive and occurs in increments. My system seemed to be banging on and off, with little or no progression.

Can anyone comment on what the problem could be? I have had to resort to switching to 4Hi when I was going up slippery driveways, etc.


Thanks,
Brian

 

[yob_yeknom]

Believe it or not, that is normal.

When the back tires have no traction and power is transferred to the front tires which have traction, banging can be felt and heard when the front tires suddenly turn and grab hold. If the back tires are spinning pretty badly and the front tires have a lot of traction, it can make a pretty friggin' hard, loud bang. That's just the way it works.
It's kind of like popping the clutch with a manual transmission, but not with the engine revved up enough to spin the tires. The tires are sitting still and when power is suddenly applied to them they make traction and the car bangs and jerks foward. So with the back tires on your X spinning and not moving the vehicle, the front tires are not turning. If they are sitting on something that they will have traction on when the power is pulsed up to them, the vehicle bangs and jerks as they grab hold and pull the vehicle foward.
With the 4 high mode the front is locked in and turning the entire time just like the rear. That way there were no sudden pulses of power to the front to cause the banging.
Did that make any sense?