Broken transfer case in Murano

A couple of times I have reported a knocking noise when starting my 2010 Nissan Murano from cold and when taking off after it's been sitting for a while, but it didn't make the noise when the dealer had it. At the 80,000km service they said the transfer case seal is leaking and would cost $800 to fix, the front lower control arm bushes are starting to crack, and the rear engine mount had collapsed and the cost to fix was $380. There was also a knocking sound from the transaxle area, but they were unable to hear the noise at the start. I booked the car in to have the transfer case seal fixed, now a couple of days after it started making a grinding noise when taking off and in reverse gear as well. I went straight back to the dealer to get them to look at. They took it for a test drive and come back and said they have not had any trouble with this before and advised me not to take the car home. The Service Manager called me and said to take the car home, but don't go interstate and drive it easy as the transfer case is no good and he was going to give head office a call to see if they would fix the car for free. The answer from Nissan was that they would not do anything about the problem. I don't think this is fair, as I paid for the transfer case seals to be fixed and now the problem is within the same area. I've now been told to take the car back and the dealer will look at it at my expense, but I want I want them to replace the transfer case as the problem got worse after they did the seals. Do you think I have a case or not?