Finally- all is explained. Regarding the puzzling question about the steel washer chewing up the delivery sleeve- they aren't intended to ever touch each other! A broken thrust washer near the rear of the transmission allowed the intermediate shaft to move back too far, causing the steel washer to collide with the delivery sleeve. And it appears that I'm to blame for the broken thrust washer, by apparently not accurately checking endplay when I last refreshed the transmission. Substituting a new .075" washer for the broken .085" one gives .013" play (in an allowable range of .007"-.015"). So it must have only had .003" play- oops! But having now explained it all, I can happily replace pieces and get it back into service.
