Kim Jung-woo opened the scoring in the seventh minute and Lee Dong-gook added a 27th-minute penalty as Jeonbuk responded to second-placed FC Seoul's hammering of Busan I'Park on Saturday.
Kim Eun-jung pulled a goal back for Gangwon, also from the spot.
Third-placed Ulsan Hyundai remained eight points back after a 2-1 win over Gwangju FC thanks to Kwak Tae-hwi's last-minute winner. Maranhao had earlier equalised after Kim Dong-sub put Gwangju ahead.
Pohang Steelers came from behind to beat Incheon United 2-1, also with a last-minute goal.
Nam Joon-jae gave Incheon the lead but Shin Hyung-min equalised and Noh Byung-joon grabbed the late clincher.