Need help identifying clunk in rear end

[nchandler]

Hey folks, I have a 1972 K20 that makes a loud clunk when putting it in reverse.
The U-Joints are good, there is no Left - Right slop in the yoke.

The yoke rotates a bout 1/2 or so inches clockwise before it catches.


There seems to be appropriate amount of play for the backlash but the ring gear seems to turn with the yoke about 1/2 or so of an inch before it engages.


What would cause this amount of play on the ring gear?

Thanks