Grease retainers? They were there once. That ujoint is baked, no question. When you install (or have installed) new ones..you will see that there is an "o-ring" type seal.
That seal will fall off and be gone as soon as the joints grease goes bye bye and what once was needle bearings turn to dust. 96 and older uses 260X series joint, 97 and newer uses the 760X or (296) series. Do not buy a joint with a grease fitting as they are WEAK JUNK. Buy an OEM spicer joint. Be sure to find the "sweet spot" when installing them as it is easy to install a joint on a bind..that tears it up in 2k miles or less. The sweet spot just means the shafts move freely in all directions after the new joint is installed. How to attain it is to apply a few taps with a hammer next to the caps and feel that the joint is centered.

SD