clunk when turning

[macdaddy70]

Good evening all. I have a 70 gmc c10 lwb with a manual transmission. I have recently noticed when starting from a stop and making a turn, there is a noticeable clunk in the rear of the truck. No issues after the initial clunk...it drives great but it does have me concerned. Does not happen when I am at cruising speed rounding corners and doesn't happen all the time when turning at a stop light. Mostly occurs when turning to the left...I do not recall it happening when turning right. I have checked u-joints and none have slack. Could this be an issue with the axle bearings or the differential itself. Any suggestions...?
Thanks for your help in advance. Hope everyone has a great Labor Day weekend!!!!