180sx2fast4u

I am currently rebuilding an F23 and Ive gotten all the pistons, rods, crank installed. Im now at the front cover and balance shafts. I have 3 seals one for the crank and I thought two for the balance shafts. I see the front balance shaft seal (brown) fits into the front cover but I am unsure of the location of the rear balance shaft seal. I have the balance shaft in and I see with the front cover on it attaches to the gear which mates to the other gear etc, but on the side that faces the block the third seal I have doesn't fit. Any help would be great, if needed I can take some pictures. Thanks