Here's a sneaky trick I've used for years when assembilng standard transmissions. The cluster gear needle bearings have to be held into place on most of them with grease, as they're loose-packed without a cage to hold them in place. The thrust washers on each end of the cluster gear are also a PITA to keep in place while the pivot shaft is inserted. Getting the cluster gear into position without dropping needle bearings or losing a thrust washer will increase your vocabulary of cusswords, guaranteed! If you use a piece of wooden dowel rod cut off to the right length to hold the needle bearings and thrust washers in place while you manipulate the cluster gear into the trans case, it will slide out as the steel pivot shaft is inserted. Just make the dowel exactly the right length to fit between the front and rear holes in the case. Sand the dowel to the right size to be an easy slip fit through the holes in the case. In a pinch, I've also used a cut-off piece of garden hose for the same purpose. My tool box used to contain an assembly dowel for Ford and Chevy transmissions, so I didn't have to cut up a broom handle or a garden hose every time I built up a transmission!
Jerry