Stellar. Thanks so much Eric, i'll try that.
BTW i did contact a local brake shop and he just said "replace the calipers, it'll cost less than having me rebuild them".
If there is something i can do myself, i'll do it (as evidenced by the numerous requests for help on this forum when i get stuck
*edit* I wish i had known that tip wrt the pistons when i had them all apart not that long ago. I replaced all 4 pads when i installed a new (used) rear diff.