Truck Repair: Drivetrain, sierra 4x4, gmc sierra

Question
Kasey,
I have a 2000 GMC Sierra 4x4 Z71 that I think has sginificant slack in the drivetrain.  When I have the vehicle in park, parking brake set, I can manually rotate the driveshaft about one inch from its static position.
What does this mean / portend about the drivetrain or transmission?
When I bought the vehicle 2 years ago, used, the emergency brake did not work, so the parking gear was the only thing holding the vehicle in place when parked....I replaced the e-brake shoes, adjusted the e-brake cables, and fixed the e-brake problem....but am now worried the drive-train may still need some repairs.
The vehicle has 103,000 miles on it and maybe time to re-build the trans? or rear-diff?
Thanks for your time, Kasey.
-Brooks


Answer
sounds like the slop is in the rearend when you put the truck in park it will slightly roll forward untill it stops on the trans so dont worry about the trans slop is the norm there when in park but you should not have 1" of travel in the rear end .. time to pull that back plate off and find the slop.thanks for the question