There are many designs for 4 wheel drive, I wouldn't use my part-time 4x4 ford truck in 4x4 mode just for rain on pavement. Maybe if it was some sort of super huge gullywasher that suddenly appeared and was floating my rear end downstream.

I think the explorer has a Full-time 4x4 system as an option.

For those of you with a 4x4 that are curious there's:

Full-time 4WD
Part-time 4WD
Full-time symmetric AWD
Automatic asymmetric AWD
and combinations

Here's a guide to the various type of 4 wheel drive systems:

http://www.4x4abc.com/4WD101/4WD-AWD-autoAWD.html

http://www.4x4abc.com/4WD101/definition_combi.html

 

AWD and 4WD are very very different. Thats why our trucks arent always in 4WD.

 

The 2006 Harley Davidson is supposed to be available with all wheel drive.

 

on a paved road in rain leave the truck in 2wd and don't gun it...if you have good tires they will handlel the wet road for you.....if you got bad tires 4 hi is useless.