4x4

I bought a 1987 Chevy Silverado with a
350 and matching tranny that were take.
From a wrecked vehicle and put in the
truck. I put a windshield in it and tuned it
up on Friday! Yesterday, I wanted to test
the 4x4 unit and so I went out and locked
the hubs in, started the truck put my shifter
in 4high, back out of the driveway, drove
30 feet at idle speed with 2-3 throttle taps
to see if I could feel all 4 wheels pulling,
and I did feel them so I stopped.
Next, I put the truck in Neutral,  shifted
back to 2 high and all hell broke loose!
Sounds like there are gears hitting each
other, and I can not get the truck to move
now!  No 2 wheel....no 4 wheel.....can't
even tow it without tearing up more stuff!
It's parked in the street on Blackwater Mo
and I have no idea what to do.
Help!!??