If its the torque converter it will eventually trigger the check engine light. At that point a hard enough code should be generated to further substantiate the analysis. On some of the torque converter cases the unit starts to deteriorate so much that it begins to whine. When this happens bits and pieces have come off the converter and are travelling through your transmission. You want to avoid the situation getting to this level because at that point the transmission will need to be replaced(remanufactured best). If you catch the torque converter failure in the early stages then you just replace this component and the trans is still good.