Td5 auto gearbox clunk

Hope you can help, my Discovery Td5 changes down with a terrible chunk instead of a smooth change. When I replaced the engine, I had to relax the bellhousing fasteners to allow the flexiplate to line up with the torque converter-could that have caused this fault?
Would appreciate any help, abuse or clever one-liners!

how do you mean, t/c was tight up to drive plate ,should be 1-2mm gap that you close by tighten t/c bolts