An electrical submersible pump assembly has modules including a pump, a motor, and a pressure equalizer. A first adapter having threads is mounted to one of the modules. A second adapter is mounted to an adjacent one of the modules, the second adapter having a tubular body, a neck, and an external shoulder at a base of the neck. A collar is rotatably carried on the neck and in threaded engagement with the threads of the first adapter. A clamp secures around the neck between the external shoulder and the collar after the collar is fully engaged with the threads on the first adapter. A pair of flanges are mounted to and extend outward from the clamp. A motor lead locates between the flanges.