Vision on teams
A team (or department/division) has a unique contribution to a larger organisation.
Why unique? If this were no longer the case, then the existence of the team would cease to exist at some point. To what extent is your team in touch with this unique contribution? If this unique contribution is lived by the team, then this obviously will contribute to an effective team.
Additionally, as pointed out before, something else is needed: TRUST. In a good team every member deploys his or her talents, and the strengths of individuals are engaged in combination with the weaknesses of other team members. There is mutual trust and respect. The team is effective, in the sense that it delivers what it committed to, and has fun in the process. Of course, there can be pressure, but this does not result in negative stress or a negative atmosphere.
There can, and in fact must, be conflicts. However by giving effective feedback in an open atmosphere, these are resolved. For a good bedding of the team is a strong well-balanced team lead helpful, and each team member has a responsibility for the functioning of the team as a whole. This includes the responsibility to speak up what is not working, and thereby staying engaged.