Ok so the problem is solved, but as there is not too much information is available on the internet, and some info is misleading, i will share my experience here.
Original Issue : Chain Slipping sound fron Transfer case only in 4H mode
Other symptoms : No Power to Front wheel in 4H-L or 4LL mode. But no slipping sound from T-case
Diagnosis: Mechanical Failure of Transfer Case.
Solution: Replacement of Transfer Case (kabli) expense of 16k to 18k pak rupees
Technicalities: Try to find a Transfer Case with original motor (actuator) attached to it, otherwise haggle and bring the price down to 14 or 15 k. You will still need a motor, taken off another T-case or your original t-case(if the motor was fine.)
Complication: This is the most complicated issue, if you dont get the original motor (never taken off) of the T-case you bought, then you wont get 4x4 function, and your 4wd ecu will detect that the motor is not calibrated and your 4wd indication lights will start blinking.
I have searched high and low on internet forums, some even say that this setup is useless and you need a complete t-case with original motor, some give a slight idea about adjusting the calibration but no method or steps.
However It is possible to calibrate an actuator motor with the new T-case, and Hameed electrician and his guys near Gawal Mandi did it for me, charged me 3000 for it, but they normally charge anywhere between 4 to 7k for this Job. It can take between 1 hour and 3 hours.. (they say it can even take upto 12 hours) but if there is no other problem in the car I dont think it will take more than 2 hours or so.
Here are the directions , near Marir chowk, Muree Road,