front caster angle question

i have ordered adjustable control arms and will be trying to align it after i install them
my question is does anyone know the relation between pinion angle,and caster/knuckle angle, and the angle of the back(or front if you are talking about the way it faces) of the case on a d30 in the front end of a '99 xj...5" lift

i have searched and understand what the caster angle should be but my angle finder is a little bulky and i don't feel like i am getting an acurate measurement on the knuckle...so i am hoping to try to correlate the angle from the back of the case to the knuckle as i can get a good measurement of of it..
i searched on gojeeps page but he was refering to two different d30's and mentioned one in a '00-02 and i was thinking the '99 was the same as these
so i am a lil' cornfused...

see if there's a good place on the upper or lower ball-joint to put it and add or subtract 90 degrees.

that's what I do with my D44, but it has lower ball-joints that are about 2 inches across and flat on the bottom.

A rough gauge is that you lose one degree of caster for every inch of lift if you keep the axle pinion yoke directly in line with the driveshaft.

For a 5" lift, you mostly likely will need to drop from the stock 7 degrees of caster down to 5 degrees, and let the pinion sit 3 degrees below the driveshaft, giving you a total of five degrees of correction for your five inches of lift. This should allow you to drive pretty much vibration free, but you are right at the limit.

I wouldn't worry about measuring - focus on how it drives and just forget about alignment specs - they don't matter. Adjust the upper arms so the u-joint angle is only 1 degree below the driveshaft, giving about three degrees of caster. This should be vibe free even in 4wd. Take it out on the highway up to 70 mph. Does it track straight and drive nicely? If so, you are done. If it wanders and tacks from side to side, you need more caster.

If needed, lower the pinion one degree, thereby adding a degree of caster (you are now at approximately four degrees of caster). Repeat the driving test.

If it still tacks and wobbles, do it again. At 3 degrees of u-joint operating angle it will probably vibrate in 4wd, but at 5 degrees of caster it should drive nicely. You can make micro adjustments...some people find 4.5 degrees of caster with about 2.5 degrees of u-joint angle is vibe free and drives well.

If it still doesn't drive straight, you'll be lowering the lift or getting lockout hubs (or putting up with the vibes).

Nay

I agree with Nay, throw the book out the window. Every rig acts different when lifted. Go by how it handles and feels. I am at 6.5” and all I used for alignment was a tape measurer.