if they are the same model of tranny, liek a 2wd w55 and a 4wd w56, then all that needs to be changed is the tailshaft assemlby of the 2wd swapped for a tcase, and the output shaft of the 2wd swapped for the output of the 4x4 tranny, that then mates to the tcase
the 2wd tranny from the 94 is a w55.... the 84 truck probably uses a g series.... you would jsut need the output shaft from a 4x4 w series tranny, and then bolt it to a tcase compatible with a w56....
