The answer is definitely 4 and the division is definitely the AFC North. Amazingly, it happened THREE TIMES.
1997: GBP (13-3), TBB (10-6), DET (9-7), MIN (9-7)
1994: MIN (10-6), GBP (9-7), DET (9-7), CHI (9-7)
1982: GBP (5-3-1), MIN (5-4), TBB (5-4), DET (4-5)
The 1982 strike shortened season featured 16 playoff teams (out of 28 teams in the league). No team had a bye, and there were 8 games on wild card weekend (4 on Saturday and 4 on Sunday). I remember it well, as I spent the entire weekend only watching football.