Conduct inside the Vehicle
You must stay off the crew intercom once inside the vehicle, by default you will join this when you mount up, best practice is to connect to Misc Channel 1. This allows the vehicle crew to communicate uninterrupted by any infantry chatter.
When in the vehicle best conduct is to not speak to the crew unless spoken to, your fireteam leader or squad leader will be on the crew channel to talk to the crew.
In some more cramped vehicles, you will be asked to keep quiet to not distract the crew during combat.