A u-joint should be installed with the grease fitting on the compression side of the yoke. What that means is, as the transmission yoke turns, it pushes on the grease fitting as it tries to turn the driveshaft. You don't want the yoke to pull on the webbing of the u-joint where the fitting is. The other end of the driveshaft is the same only the driveshaft yoke pushes on the fitting as it tries to turn the pinion yoke. The grease fitting should be pointing at the yoke with the most clearance, usually the driveshaft.
Joe
