When you say "teamed" I take it you are talking about an etherchannel?
Well you should have an etherchannel interface like interface po1 (port-channel 1) for example.
Just make any changes you require to the port-channel interface and NOT the inidividual interface that make up the port-channel group.
If you make a change to the and individual interface you WILL bring down the etherchannel and you WILL have downtime.
To add vlan 6 to the etherchannel you just need to enter the interface po and add the vlan with:
#switchport trunk allowed vlan add 6
regards,
Ian