I just installed a new transmission in my car and had to remove the front driveshaft to do so and had the same problem. I got it back together, which isn't easy. I put all the balls into that ring, aligned the balls on the driveshaft knuckle while in the ring moving them to were they're supposed to be, right on the very edge though is where you want to align them. Then take the casing and line it up while holding the ring on the very end with the balls align, push the casing on over the ring as you push it on the knuckle. It honestly took maybe 15mins to get it on there right after my bro in law screwed with it for hours so I think it's a hit or miss and want to smash stuff kinda thing. I then pryed the other end of the casing off while it was all assembled, then packed the little disk that pops off full of grease and pushed as much grease into the knuckle casing assembly as I could. Not a gaurenteed assembly procedure because I'm currently having a vibration in front that I think is from the front driveshaft. But I got it together and everything moved easily and fluidly. You basically have to put the ring into the casing and on the knuckle at the same exact time. WHY FORD WHY MUST YOU MAKE THINGS SO DIFFICULT!?