Hi,
I currently have a Disco TD5, but i fancy a TD5 Defender, If is was to change the transfer box gearing to that on the Disco and sound proof it (exmoor trim kit etc) and maybe chip it, is it going to be any good on the motorway compared with the Disco?

probe about the same!

why would you want to make a defender drive and sound like a discovery?..if you want something that is as fast and as quiet and as comfy as a discovery on the motorway buy a discovery..if you want something that is the best fun youll ever have off road,,aint gonna break the speed barrier and is noisy and drafty and reasonably comy get a defender,but it aint gonna drive nothing like a discovery,but in my opinion is great fun and always brings a smile to my face

Aye although the disco and defender share the same basic set up of engine transmission etc they really are totally different. Sounds like you want the comfort and convenience of the disco but the "cool" of the defender. You can't have both.