The best way is to get a straight peice of round stock steel that is as close in diameter as possible to the splined end of your axle shafts. Remove the shafts and slide the steel rod through the housing so it protrudes from each exle flange (if you have a thrust block installed you'll have to take it out to be able to slide the rod through). Then take mesurements from the top and bottom of the rod to the bearing bore. If the measurements between top and bottom aren't equal on either tube then it's bent up or down relative to the centerline of the differential case.
'84 CJ-7: Yota axles (spartan locked front, e-locked rear) 4" BDS, 1" Daystar & 3/8" shackle lifts, 35" X-Terrains on steelies, YJ Tub & family roll bar, heater blower upgrade, 4.2L w/MC2100 & Team Rush, Warn 8274. Rebuilt 4.2/4.0 hybrid, AX15 and twin sticks/clocking ring waiting to go in.
The advertised position for a topless, dirty jeep girl has been filled......by my wife. Thanks to all that applied.
<------------and yes, that is her. :-D