Can HA or fail-over work with difference version?

Hi, would like to get some input. We have a 1 pair LTM 3900 and planning to upgrade the version from BIG-IP 11.1.0 Build 1943.0 Final To BIG-IP 11.4.1 Build 681.0 Hotfix HF8. This upgrade only done in 1 box. After the upgrade, 1 box will using version 11.1 and another box will using 11.4 and remain for 1 weeks before upgrade another box. During this period, can the HA or fail-over will work as normal? Can another box (standby) take the traffic if the active box down? Thanks