I have a 2003 Sorento with a 3.5 engine. When it is shifting between 1st and 2nd I hear a knock in my engine. At idle the knock is not there. If I rev it a little I hear the knock but if I rev it while in gear and foot on the brake it is quiet. I am ruling out a rod knock because it is not always there. Could it be a collapsed lifter? Has anyone else had this problem? it will not knock under load.