So maybe he feels a little proud over the fact that he managed to (unintentionally), make Optimus cut himself off. Hips canting into the touch, charge collecting at each deeper dig and skittering away down his circuitry as the stroke was begun again, Cliffjumper nearly laughed around the audial, but cut it to merely humming.

Gently gripping the slender thing between his teeth, Cliffjumper dragged downwards along it while he raised his other hand to - slightly haphazardly, since it was hard to see what he was doing - stroke the wheel set in the opposite shoulder.