I've just got myself two new rear axle bushes for the A4, as the old ones are "slightly" worn... I've noticed they have huge voids in the back of them, hence wondering about polyurethane filling the voids. I've filled mounts before, but usually ones that are supporting engines and suchlike, whereas these bushes are being subject to constant twisting forces around its axis as the axle moves up and down Just wondering if anyone else has poly-filled a bush thats being used in this type of location before? On one hand it seems that it would make it stiffer, improve the axle location etc, but on the other i'm worried that it will start limiting the rotational movement, and stop the axle doing its job? Any ideas?