Firstly, if you don't know it, the rear u-joint (68 C-code with C4) has 2 small caps and 2 large caps. The large caps go in the differential pinion and the small caps are pressed into the drive line. Secondly, the grease nipple on this particular part sucks. You cannot get a standard sized grease gun to fit between the caps to grease it. Forget even trying once it's on the car which is the only time you can grease it since the large caps have to be held in place on the pinion to grease it at which point... it's impossible.