Need some help understanding this. The u-joint manufacturers seem to say they want a 1-3 degree offset in alignment to get proper u-joint rotation for even bearing wear in the caps. So if this is the case why do we go through so much trouble to ensure the driveline is perfectly straight? Shouldn't we actually be looking to have the height offset enough to create the 1-3 degree offset that is best for the u-joints? That is after all the purpose of drive alignment, right?

The purpose of the drive alignment is more centered towards making sure the shaft section that rides on the gimbal bearing and extends into the coupler is straight. You'll get u joint angle every time you trim and turn.

X2 You are not aligning the u-joints, you are aligning the input shaft between the gimbal bearing and the coupler.

Amen to the comments

If not aligned it will tear up the splines on the coupler and drive shaft. Make sure you check this every 100 hours

3pointstsr

I completely forgot about steering and trim allowing for movement of the u-joints. On an SSM installation there is no bearing to align with though, correct?. The output shaft of the drive with the u-joints plugs directly into the back of the trans, right? I guess I was thinking you'd want the 1-3 degree offset at the most commonly trimmed position of the drive. Just trying to learn the why's of what we do for a better understanding of the whole thing. Thanks

ive seen when you do the alignment ,if you turn the motor 180, its off some when you stab the tool again.

As Vinny P said, alignment of Bravo style drives is to align the gimbal bearing and the engine/coupler. If the engine angle isn't correct, the spline shaft from the drive will not want to go all of the way into the coupler unless the engine angle is correct. This isn't really to set the angles on the u-joint, that is by design between the gimbal bearing, trim/steer pivot pin location, and the location of the drive on the transom bellhousing.
SSM drives don't have the gimbal bearing, but the final goal is the same. Proper alignment of SSM plug-in drives is center the tailstock (no gimbal bearing) "and" to keep "equal" angles of the 2 crosses throughout the trim and steering range, within reason of course.

Here is some basic info explaining equal angles, double cardan joints and shafts: http://en.wikipedia.org/wiki/Constant-velocity_joint and http://en.wikipedia.org/wiki/Universal_joint