$(function(){
    $('.fadein-gears img:gt(0)').hide();
    setInterval(function(){
      $('.fadein-gears :first-child').fadeOut()
         .next('img').fadeIn()
         .end().appendTo('.fadein-gears');}, 
      5000);
});

$(function(){
    $('.fadein-wheels img:gt(0)').hide();
    setInterval(function(){
      $('.fadein-wheels :first-child').fadeOut()
         .next('img').fadeIn()
         .end().appendTo('.fadein-wheels');}, 
      5000);
});