grub2-install failing after RAID 1 HDD replaced

[Kilburn Abrahams]

I upgraded a gentoo box which has RAID 1 from 350GB to 1TB drives. Then I decided to upgarde from grub 1 to grub 2.
Steps:
1.  installed grub 2 V2.02 beta 2

2.  checked /boot/grub/device.map (all looked fine)
     (fd0) /dev/fd0
     (hd0) /dev/sda
     (hd1) /dev/sdb
3.  grub2-install --grub-setup=/bin/true /dev/sda
     Installing for i386-pc platform.
     grub2-install: error: disk `mduuid/c845d9551ec0b439cb201669f728008a' not found.

blkid is returning this.
 

/dev/md0: UUID="b75a81b5-59c6-4eb8-aadc-66650f5ea1bd" TYPE="ext2"
/dev/md2: UUID="3211adef-bf44-41d4-86bb-164b46c3d909" TYPE="ext4"
/dev/md1: UUID="6036ef9a-878e-45ce-b5b3-bec8cd920fd2" TYPE="swap"
/dev/sdb1: UUID="c845d955-1ec0-b439-cb20-1669f728008a" TYPE="linux_raid_member" PARTUUID="6795d2bc-01"
/dev/sdb2: UUID="e1c7ed62-0e38-d06b-cb20-1669f728008a" TYPE="linux_raid_member" PARTUUID="6795d2bc-02"
/dev/sdb3: UUID="18a2e9e5-05d5-4ba4-cb20-1669f728008a" TYPE="linux_raid_member" PARTUUID="6795d2bc-03"
/dev/sda1: UUID="c845d955-1ec0-b439-cb20-1669f728008a" TYPE="linux_raid_member" PARTUUID="6795d2bc-01"
/dev/sda2: UUID="e1c7ed62-0e38-d06b-cb20-1669f728008a" TYPE="linux_raid_member" PARTUUID="6795d2bc-02"
/dev/sda3: UUID="18a2e9e5-05d5-4ba4-cb20-1669f728008a" TYPE="linux_raid_member" PARTUUID="6795d2bc-03"

The HDD are formatted as
/dev/sda1 * 2048 67583 65536 32M fd Linux raid autodetect
/dev/sda2 67584 12355583 12288000 5.9G fd Linux raid autodetect
/dev/sda3 12355584 1953525167 1941169584 925.6G fd Linux raid autodetect
/dev/sdb1 * 2048 67583 65536 32M fd Linux raid autodetect
/dev/sdb2 67584 12355583 12288000 5.9G fd Linux raid autodetect
/dev/sdb3 12355584 1953525167 1941169584 925.6G fd Linux raid autodetect

Is there something I am missing? I am using mdadm 3.3.1 but can upgarde to 3.4. I believe grub2-install calls mdadm via grub2-probe, is this what is causing the problem, if so, how can I correct this?

Thanks

Kilburn