[Killer Bee]

short answer is no, 4" of lift does not automatically or categorically necessitate driveshaft lengthening..

can a 4" lift in some circumstances require driveshaft lengthening? sometimes but not always..

can lifting a 4wd vehicle create transfer case leaks? yes, but not necessarily by virtue of lift alone..

slip yokes are designed to operate within a range of suspension travel, some accomplish this better than others..

worn yokes and seals simply running in different positions can create leaks where otherwise parts in better condition would not leak..

short wheelbase vehicles may experience driveline angle issues more so than overall length issues..

suspension travel is also an important factor that dictates required driveshaft lengths, yoke engagement, u-joint type, etc..

apologies for the vague answer but there is a myriad of criteria to consider for a proper answer to your question..

knowing exactly what you're working on, exact lift from stock height, method of lift, etc. will yield more accurate responses..

please share some details about your project and good luck!