You're driving it WITHOUT the (rear) driveshaft, and it still shakes? Probably not that driveshaft, then. 'Course, the transfer case output shaft isn't supported in the bushing with no driveshaft yoke in place.Tried back to front tire swap, feels the same. Should have driveshaft back and in by Wed/Thurs.
Bent wheel, bent axle shaft, bad bearing(s) in the axle housing somewhere, maybe a chipped ring 'n' pinion gear.
Potentially the FRONT drive shaft, or in the front axle--but that often shows up as steering wheel shake.
If it was engine or torque converter, it'd do it in neutral.