Front driveshaft vibration, wtf

so my jeep vibrates at over 30mph, took out the front driveshaft, vibrating gone. Put friends front driveshaft in, worked perfectly fine. So my driveshaft is shot in some way shape or form. This is all right after i regeared to 4.56s and hooked it up for the first time so i understand its spinning faster now. Fleetpride wants 100 dollars to balance it for some reason, so im wondering if theres another possible culprit than balance here. ujoints? i dont know whats involved in checking them or how easy replacing is. just lookin for a little guidance, what should i be lookin for when looking over this front shaft? thanks all

check the slip, if there is any play in it that is what is causing it. on mine before gearing it did not vibrate even though there was a very very small amount of play, after going to 4.56s the vibes were rather bad and it was from that small amount of play in the slip. rebalancing it wont help if parts are worn out.

This just happened to me. Regear and bad vibes from the front. Never had vibes up front before. I spent the $60 to replace my ujoints and found the CV joint bearings were trashdd s~!I took it to a@drivesh@nt place. They also found bad splines. Had it rebuilt and balanced (new CV joint, ujoints, bigger splines..$230), no more vibrationr fr~o the front.

Go to a junkyard and get another one.

K