I have several versions of the AM Pacific covering several runs, including the first run. None have experienced the universals (or anything else in the drive, for that matter) breaking.
When the Pacific first came out, we ran one at a Scenery Unlimited open house for five hours non-stop without any trouble.
Also, all AM diesels, except for the first run of GP 35's (they use a spring!), have plastic universals, as do the former SHS diesels. I've logged quite a few miles on most of my AM and SHS motive power without incident.
Rusty