Loss Of Traction

I have purchased a Disco 1996 Tdi to replace my defender, the first week i had it the clutch went and so we have now a new heavy duty clutch fitted. I took it out today for a test and find that it is great on road and it is ok at pulling up small hills etc but when i tred it on a steeper hill( railway embankment) it drove up about its own length and then would go no further, it didnt wheel spin even though my foot was right of the clutch, it just reved and done nothing more, i was in Hi box with the diff loak on, the car is modified with a 2" lift and 33" BF Goodrich AT's. The defender goes up this kind of hill no problem and if it cant it would at least spin its wheels, this just wont. I could understand it spinning as the tyres dont seam very good in mud but there was no spinning at all.

I dont know Disco's and I am very disapointed that it wont do anything like the defender does. Can any one help me please.(New User) also does any one have the same problem with these tyres.
Thanks
Kevin

the engine is exactly the same as in the 300tdi defenders. therer is obviously a problem with this disco

the problem part i know, the cure i dont, any ideas?

Sounds like the new clutch was slipping.
Is it adjusted correctly? or possibly oil leak onto new clutch?
Did it smell after spinning the engine?