What do Transfer Case Drop Kits do? They drop your transfer case. When you lift your truck there are several things that must be considered. One of the main areas affected by a lift is the angle of your drive line. That angle at which the drive line goes into the T-case must be correct or you can get a 'growl' or drive line vibration. These transfer case drop kits are designed to lower the transfer case to correct the driveline angle of a lifted truck. If you purchased your suspension package through Jack-it and a transfer case drop is necessary, it will be included (except the Jeep XJ kits).