Posted 31 March 2013 - 08:22 AM
I am guessing that you have renewed the knuckle joint, as you should do every time there is major maintenance in this area. (You don't want the cup wearing through, as they do, resulting in a scrapped arm.) The new cup more often than not does not seat fully in the arm at first, possibly due to trapped air behind it, or just because the nylon cup is slightly oversize for the hole to make it a tight fit. Ordinarily it sorts itself out as soon as there is weight on the wheel, so raising the arm with a jack, maybe up and down a few times, will most likely sort it out.
If the subframe is out of the car, or its rear mounts are undone so it can be lowered, you can use a cone compressor, as you would at the front, to compress the cone slightly to help get things together. You should not have to, but I needed to once, just a length of threaded rod, as there was no need to apply the huge amount of force needed at the front, maybe about 1/4" compression of the cone. When it was all assembled and the car bounced a few times, it settled nicely at the correct ride height.
The other possibility, if you have used a non-genuine subframe, is that it has been made wrongly, and if so the supplier is entirely liable, so take it back and demand a full refund. If they refuse, Trading Standards is the next place to go.