Like an idiot, I didn't measure before ripping out my whole suspension. I want to make sure I get an acceptable caster angle when welding the perches on top. Seems like it would be a whole lot easier to set caster by measuring pinion angle using the flat on the pumpkin housing that looks like it was made for a magnetic angle finder.

Anybody know this measurement or care to check out you jeep. I'd also like to know what you caster for the given pinion angle. I believe the factory caster spec is 7.5 +/- .5 deg. (87 YJ)

Set the purches on it, put the weight of the Jeep on them, set the caster angle and weld. This is the most accurate way IMHO.

What dean said, with the addition:

If you're going to run 4wd on the street, set pinion angle and you get what you get for caster (unless you turn the knuckles).

If not, you can probably set the caster you want, and accept the pinion, as long as the pinion angle isn't way off.

But the only way to do it is with the weight on your axle.

You should also make sure the new perches are parallel to the old. That would prevent the caster from changing.