The problem is that the clutch pressure plate is spinning, but the pushrod is not. So how do you make them work together?
The original design used a single large bearing between the pushrod and lifter, because the lifter was directly contacting the spinning pressure plate. This bearing allowed the lifter to spin.
In 87 they changed the design to put three small bearings between the rod and lifter, and lock them together (I think because people kept loosing the single large bearing on the other design). But it still wore out very fast, because the lifter still spins when it contacts the pressure plate.
The 89 update is a much more robust design. Instead of putting a bearing between the rod and lifter to allow the lifter to spin, they put a needle bearing between the lifter and pressure plate, so now the lifter doesn't spin. Since the lifter isn't spinning, it lasts much longer.
The 89 update will not cure a slipping clutch, it doesn't fix your springs or add more pressure. It only changes the way your clutch disengages. It only replaces the lifter and pressure plate, it doesn't change the springs, worn clutch fibers, steels, or anything like that.
If you have to pull your clutch in really far to get it to disengage, and all your adjustment is used up, the 89 update might very well fix that. But if it your clutch is worn out and is slipping, the 89 update won't do anything at all.
