carl, some good points, except the driveshaft must be taken into account in the overall scheme and out of spec #'s WILL cause excessively worn u joints, and could lead to annoying vibrations. the working angle must be as close to 1* as possible, and the difference cannot exceed .5* btwn them. i didnt make this up, spicer (the largest mfg) did. if you just set them the same, you could be looking at some out of spec working angles, especially if the car is lowered a lot. i had to raise the back of my tranny 2" to get my numbers within spec. raising the tranny decreased its angle and therfore required a change in the pinion angle.
when was the last time one of those large 4x4's was doing 80+ on the freeway. when was the last time one of those large 4x4's ran tires that didnt make the truck shake to begin with. my point is, a car set up to run fast and quiet is much different than a truck whose tires alone are louder than the stereo, and thats my stereo when im driving next to them.
the pinion must match the trans, but they can also be equal and opposite. if your pinion is higher than the trans, you can actually point the rear of the trans down, and also point the pinion down ( like this \____/ ). again as long as the working angles are within .5* of each other (pinion can be .5* different to account for axle wrap), and as close to 1* as possible without being under, everything is optimal.
also, dont worry about the car being at parallel. the drivetrain doesnt care about that. put it at ride height and start measuring.
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