In Connector it is possible to pick up updates to synchronized entries.  This is the scenario... 

In AX you enter a sales order with one line and the sales order is synchronized to CRM by the Connector.  In AX if you change the quantity on the sales line or add a second line to the sales order how do you get the update to the sales order moved over to CRM? 

The answer is you have to configure the database to do change tracking.  In SQL server on each database there is a change tracking property that is set to False by default.  Change this to True and set the Retention Period property in SQL to the length of time you want the changes kept, like 2 days.  Once you have set those properties restart SQL server for the change to be enabled.  If you are on AX 2009 and Connector FP6, restart the Connector service and you should start seeing your updates get moved over to CRM.  If you are on AX 2012, rerun the DynamicsConnector class in AX in order for the web services to detect the change in the database properties.  Once you've rerun the class, restart the Connector service and you should see your updates get synchronized.