steering pulling problem

Ive had a long time problem with my steering, first it was pulling to the left, had the tracking done and it was fine for 4 weeks, took it back and the drop arm ball joint had play in it, fitted a new one and had the tracking redone, all fine then for another 4 weeks, then car starts pulling to the right and I have a cluncking sound under my feet, find the cluncking is the radius arm bush so replace all suspension bushes with polybush kit hoping that will sort the steering pull, it doesnt, take it to have the tracking done again, it was 1.5 degrees out, drive down the road and its still pulling to the left, take it back to the garage and they double check and the tracking spot on, although the steering wheel is slightly off center when driving straight. I remove the front wheel and find that one of the pads has been dragging, this turns out to be a slightly bent guide pin on the caliper, this is replaced and the wheel now spins freely, try driving the car thinking that must be it and its still pulling to the right, had the tracking checked again and its spot on. Now though I have developed a knocking noise from the steering box, when waggling the steering wheel with no load on it, not 100% sure if its excessive backlash or if the shaft has a bit of play up and down, can you adjust the backlash on the TD5?, or do you think it needs a new box, I go away in 3 weeks and dont want the steering going during the journey?:doh:

cheers Lads

sorted it, it was a tyre problem, had new tyres put on and the pulling is gone