Originally Posted by TJ_Jerry
I thought so too but it just seemed that keeping the pinion angle lined up would keep at least the rear u joints under less stress ? I could be full of s**t too !
With a standard driveshaft like yours you don't want the pinion angle "lined up" with the drive shaft.
This is a pic of how a standard driveshaft should be. you want the pinion angle to match the angle of the output shaft on the transfer case, basically parallel
Adjustable uppers allow you to properly adjust the pinion angle. This is especially important when you have an SYE and CV driveshaft because the pinion angle must match the angle of the driveshaft to eliminate vibes.
Transfer case drops lessen the angles on your standard driveshaft and help make the output shaft angle and pinion angle close to parallel to reduce vibes. If you don't have any driveshaft vibrations now then you should be fine with your stock uppers.
If you decide to step up to and SYE and double carden CV shaft, you can ditch the transfer case drop.And then you'll need adjustable uppers to correctly set pinion angle.
Hope this helped