Yep it's a common issue! But not normal. I bet it feels like somebody as bumped you in the rear of the vehicle don't it. If you have a two piece driveshaft and I'm about 100% sure you do. Take the drive shaft apart and clean out all the grease in there. Then take some grease and slide on the splines,take the grease fitting and remove the ball that keeps the junk out. Install the driveshaft and see what happens I bet you it will be gone. The cause is air and to much grease cause's the shaft to bind up then it will slide down and you feel the bump or jump. Hope that helps you out.
