clicking/grinding noise from rear when turning after warm up

Here's some simple places to start...is the ABS light on, how r the U-joints...how's it braking? Try slammin' on the brakes whilst in reverse n see what happens. If that doesn't produce more certainty, jack up the pickup with both rear tires off the ground, put her in gear n get under the pickup n listen. Do you have limited slip? Notice if both tires turn forward whilst in gear or if only 1 turns. If u have an LSD, then the clutches mite be disintegrating. Pull the drums n make a visual of the brakes n check the end play on the axles.