87 4 speed electronic overdrive. recently replaced the rubber driveshaft coupling(or flex disc, or whatever you'd prefer to call it) along with the bearing where the driveshaft meets the transmission. in doing so i ended up completely taking out the drive shaft. i made sure to mark the far side of the drive shaft(where all the splines are) but my markings ended up being a little hard to make out exactly.

now there seems to be a strong vibration when i get to about 45+miles per hour. i've been told that this can be caused by that joint being off just one spline, or that it could be my universal joints.

the vibration is constant regardless of whether or not i'm accelerating or not, just as long as i'm at the speed of 45+. so i'm told by someone else that since it's vibrating regardless of whether or not i'm accelerating(if i'm coasting) that it's more than likely not the u joints since they should only vibrate when under load.

i'm new here and i'm not even sure if this is the right forum to post in, but any responses would be helpful.

thanks