Agree, I just asked the question in theoritical sense.

Since Wrangler is designed for offroad as first priority, I agree that no one wants to add center differential to it so it can be used on dry road.

I raised the question simply asking the theoritical
posibility to convert command trac to select trac

After reading the select-trac description on jeep site,
I got a little bit confused because it says it is
the transfer case that distributes the torque between
front and rear axle. Does it mean the transfer case
somehow behaves like a center differential, or is there
a center differential inside the transfer case?

Regarding your comments below
我以前強調4X4是因為總是有人說吸能，吸能。可我就是覺得梯形大梁的4X4最抗撞，最安全。哈哈。

My current feeling is,

in situaiton such as SUV against Sedan,
梯形大梁 makes SUV relatively safer. Because SUV's
hard body can easily cut into Sedan's crash zone first.


in sitation when hitting Wall or some BIG, concrete obstable, at low speed, maybe softer sedan is
safer.

My theory base is,

if the sedan's crash zone can absorb energy completely before the wall reaches the driver's compartment, the driver can be safe.

In the same situation, when SUV hits the wall, since its body structure is usually tough and hard, it is
a hard crash and can cause bigger concussion on driver.

Of course, when the speed is too big, then the crash zone can not absorb all energy, then the driver is in dangerous state. While SUV have a better chance to
keep driver in one piece.

This is like wrapping an egg with cotton or metal.
then drop it to the ground.
At low height, egg wrapped with cotton may survive
while egg wrapped with metal broke

At big height, the egg wrapped with cotton is completely flatted, while the egg wrapped with metal
is broke, but not that bad.

Since the HIGH way safety test is usually a low speed
crash against wall, so many sedans win a better score than SUV.

So talking about overal safety of vehicle, we need to
at least know this factor
ratio of vehicle-vehcile crash vehicle-wall crash