4x4 clunks on highway?

[koning56]

Hello, it seems that on the highway the 4x4 suddenly goes on off for no reason. Which goes with a loud clunk.
I'm driving in auto 4x4.
It's a 2000 ford explorer 4.0ltr xlt.
Thanks in advance for helping.

 

[Benji-Man]

First thought was, are the tires all the same size and approximately the same remaining life expectancy. The A4wd feature could be sensing different diameter tires.

My explorer engages hard with small icy patches on the road, it's got open differentials, which i believe makes the engagement even more noticeable.


The same type system in my Expedition, with Limited slip, both rear wheels are trying to pull upon engagement of the transfer case and eases the lurch felt.

 

[my98nnj]

What makes you think it's actually the 4wd making the clunk?

 

[koning56]

The tires might be a reason. 1 tire is softer then the others. I will fill them asap and check what happens. Hope this simple solution is it. Thanks.

The reason I suspect that's it's the 4wd engaging on/off is because it's same sound when I push pedal to the floor on a snowy slippery road.