Hi. I have a 1999 freelander and I had a knocking noise as yours. I was not sure if my noise was coming from front or back, it turned out to be the diff, eventually it got worse and the car was climbing itself in reverse, my local garage took out the diff, so it was only 2 wheel drive, the noise got worse, so finally to save money they suggested taking off the driveshaft. The Freelander I think is the only 4x4 that can run without the driveshaft to rear. That cured it without spending a fortune on a new diff. It's only a front wheel drive now, but I do not use it off road so no problem It cost me about £100 for all the work instead of about £650 for new diff and labour. Your knock might be something else, but if it's the diff Hope this helps.
Regards,
Alan
Alan
January 2009