[My 2003 SS Had Switchable 4x4]

You are definitely correct, yes the switch is functional and it does go into 4lo

[My 2003 SS Had Switchable 4x4]

That is what I am wondering, it does have a rebuilt title, but whoever fixed it did a fantastic job.  I would figure that maybe if the damage was that bad they went ahead and swapped it.

[My 2003 SS Had Switchable 4x4]

Where is the best place to verify the VIN?

2GCEK19N631318850

[4x4 issues]

Is this on a SS?

[My 2003 SS Had Switchable 4x4]

Was this factory installed or done after the fact?  It has the 2wd 4wd and awd button......