Could very well be locker-related, only one real way to find out . . . (acually, two, jack up the rear with the x-case in neutral and spin one wheel. If the other wheel goes the same way, Locker Ho!, if it goes opposite, open dif)
However, while I did not fully understand what you say, the angle of your driveshaft, and all of that other good stuff, should have nothing to do with your problem. Basically, everything remains constant, and the fact that you are under throttle, or steady, or coasting, can't be affected much but the angle of the drive shaft. I just figured out what you were saying, and I think that out of square suspension geometry may be the problem. Read on . . .
But, remember, that the force of the pinion turning tries to move the axle around a bit as it spins the ring gear (creep). This can cause squating under hard acceleration, and the forces are always present to some degree.
How are your rear springs and bushings? really tired stuff can, I think, show up in what you describe, but I didn't think it could be so severe. I have all new suspension on my CJ, and I can still feel some wander that is related to my right foot. It's the nature of the crappy steering and the short wheelbase (even shorter on your CJ-5). You may have just the usuall "exciting" highway ride.
But I'd make sure everything on the suspesion is in good order and torqued to spec. I'd even go for some poly bushings as well.
'82 Scrambler - NV4500/4.5" lift/33" Toyo MTs/4.0/twin stick, and my windshield washers work! Full 1/2 cab Cage
2004 Grand Limited 4.7 HO - OH Boy!
2010 Grand Laredo 5.7 Hemi - SICK - work vehicle -gone - replaced by an 08 Tahoe - nice ride.
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