[DanEC]

Maybe I missed it in all the above posts but the angle of the driveshaft is only one small part of the equation. What you need to know is the angle from horizontal of the differential pinion shaft/yoke saddle. Then you need to measure the angle from horizontal of the transmission output shaft/yoke saddle. This can usually be determined by rotating the yoke to top dead center and put an angle finder on top of it. I've had to sometimes put a big socket on top of the yoke saddle and the angle finder on top of that.

At normal ride height you want those two angles to be as close to the same as possible, regardless for the moment of the difference in height. In other words if the differential is angled down to the front 2 degrees and the transmission yoke is angled down to the front 2 degrees then that is what you want. If the differential is 3 degrees up to the front and the transmission is 3 degrees down to the front, you will have vibration problems. Then the difference in angle of the driveshaft needs to be measured and the resultant angles between it and the differential pinion and then betwee the driveshaft and the transmission shaft determined.

I know that at least a couple of degrees minimum (between driveshaft and pinion and driveshaft and transmission) is required in order to generate proper rotation of the needle bearings. I don't remember what an approximate maximum angle difference is - probably depends on U-joints, yoke knuckle clearances, etc.

Getting the driveshaft more level isn't the issue. Getting the pinion and transmission output shaft angles as close to the same as possible at ride height is what's important.