回复：dont fooled by the name!!!!

Again, here is the words quoted form Wikipedia

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Selec-Trac offers full-time all wheel drive in addition to the part-time 4WD of Command-Trac. Full-Time all wheel drive has the ability for the front and rear axles to rotate at different speeds, making driving on dry and wet surfaces possible year-round without shifting back to 2WD again. It still has the ability to lock the front and rear axles
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To me, it sounds the major difference between Select-Trac and Command-Trac is

Select-Trac provides a lockable center differential.
When not locked, it provides the vehicle the ability
to engate in 4wd mode even on dry road.
When locked, it behaves the same as Command-Trac,
which provides 4H and 4L option that can not be engaged on dry road.

My original question is
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Given a Wrangler with command-trac, then upgrade it with a lockable center differential, can it become a Select-Trac system?
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As for engaging 4wd on dry road, I know you are not big fan of it. But I can tell a personal story that
sometimes it helps.

I used to have a Honda Civic, on rainy days, when I accelerate this car from stop light, I can feel the slippery of the rear wheel.

Now I am driving a RAV4, in the same situation, I feel
more sure footed and never felt slippery on the real wheel.

Subaru offers AWD rally cars which performs really well
on dry road too.