Using Route Code in Sales/Transportation

My client is implementing JDE Transportation module in early 2015, they are on E-1 9.0.  They would like to enter a value in the Route Code field on the 'Additional Header Information' tab on the [Sales Order Header] form in SO Entry, and then have that value populate to the Route Code field on the 'Shipment Revisions' tab of the [Shipment Revisions] form. 

We have found that, if the Route Code is entered on the Billing Information form in the Customer Master, then it will update to the SO Header, SO Detail, and the Shipment Header.  But, if the Route Code is entered directly onto the SO Header, it will default to the SO Detail, but not to the Shipment Header.