In a GTR its not only the added weight of the drive chain and all 8 clutch plates in the transfer case, extra tailshaft, diff centre, drive shafts, brake rotors, wheels etc, but friction between all these individual components, also heat and energy being dispersed in many little directions by vibration can also cause loss of power. Remember the more power you have the more friction is created between components like gearsets etc. A GTR we had on the dyno had 270AWkw and then 330rwkw. So there's 60kilowats just in the removal of the front driveline, remove the rear driveline to get flywheel kilowatts and your probably looking at another 35-40kw+++