Is it necessary do to have a front double cardan driveshaft on a 4.5inch lift, no extreme wheeling will be done with this build

 

At 4.5 the difference in the angle between the output shaft of the transfer case, and the input shaft (pinion) of the differential becomes pretty severe. This typically has to be compensated for, one way or the other. The existing 2 u-joint setup can not usually deal with that amount of direction change in the drive shaft without bad vibrations or chewing through u-joints every year (or both..typically). This additional stress will also help cause pinion seal leaks at the differential. Transfer case drops (lowering the cross member), slip yoke eliminators, customer rear drive shafts (using a front shaft with cardan), and axle pinion angle adjustment shims are all used to try and correct the the angle between the transfer case and differential, or at least get it back into a reasonable range that won't result in vibrations or other problems. It is on the road, under torque load, and at speed where these problems will drive you crazy.

So the short answer is probably...yes. You'll likely have to do -something- to account for the angle difference the lift has created.

 

at speed on a Highway the issue is problematic, due to excessive vibration, unless action is taken to compensate the angles