After replacing the engine on my Td 5 I found that the flexiplate was very tight against the three torque converter fixing holes. The only way to align the bolt holes was by undoing all the bellhousing bolts a few turns, which relaxed the flexiplate against the torque converter allowing everything to line up. I've now got a gearbox that changes down with the worst thump ever-especially the low gears. Is it just a coincidence, is the box faulty or maybe there's pressure against the lockup clutch, stopping the gears releasing on change down?