In spin direction, the pulley "climbs" up the shaft pushing upward against the brake rotor to release the brake. At the same time the shaft is pulled downward. Inside the transmission, the shaft goes through the input pinion gear and then the stop collar. Under the pinion is the clutch consisting of two washers, one stationary and one splined to the shaft (rotates with shaft). There should be very little downward movement of the shaft. The stop collar pulls down on the pinion which forces the clutch washers together. The pin that holds the stop collar may have sheared off. In some transmissions, a C clip is used instead of a stop collar and pin. Not sure which one yours uses.

Eric

Here's a photo of one with a broken stop collar pin

Doesn't make sense. The only time there is any pulling down of the shaft is in spin cycle. The pulley bearing is pushing up on the brake rotor causing the pulley hub to pull down on the shaft. The amount of downward movement of the shaft is miniscule, just enough to squeeze the clutch washers together. In agitation direction, the pulley winds back down the shaft til it hits the stop but there is nothing actually pulling down on the shaft at this point. The dust cap is pressed onto the pulley so I don't see what would be popping it off. Does the washer agitate ok? Is the popping off of the dust cap the only problem?

Eric

I put the clutch plate, pinion gear and lip seal in the transmission and have the unit back together. So far so good. Evidently a few thousandths wear on the clutch washer and nylon pinion was the culprit. Additionally replaced tub bearing, lower bearing and tub seal
Thanks for the pointers. I had serviced a lot of dependable care washers but only a few transmission replacements. So today is accounted as an educational experience. Too bad this unit is no longer made.