Happens on the highway, putting the tcase in 4wh makes the vibes go away, I can put it in 4wh for just a second and the vibes go away for a while. I had the front driveshaft rebuilt, all Johnny Joints are good, alignment is good. New transmission mount. Nothing is loose and it drives great besides the vibes. It almost feels like it's pulsating. I had new gears put in about 4 months ago. Any ideas?