2000 Jimmy transmission

I've discovered a slight noise, when my truck is on drive or reverse only, but when its on neutral, is ok.... yes I've changed my trans. filter and the previous one look clean.. http://www.automotiveforums.com/vbulletin/images/icons/icon7.gif 150000km
??? could it be a bearing behind my Torkconverter... I just don't have a clue..
Did anyone out there had a simuler problem..