Thanks, Blaine. "Resonate" was the word I was searching for and Flowmasters are about the worst for doing it. From that website, there's a Magnaflow dealer about 3 miles from my home.
Just FYI, if you have an interest in a deeper tranny pan (more fluid volume, about 3 more quarts) for that Allison, the part # is 29536522 at < 50$. Another part # used is 29536891 or 29537966 for the new suction filter and tube extension for the filter at ~ 22$. Draining and removing the old pan, and putting on the new pan will require you add back 11 and 1/4 quarts of fluid. I've got one but haven't installed it yet.
