Well, after spending some time looking at the Factory Assembly Manual and re-education myself to the proper terms for the cross members of an AD truck (yes I fell like a dummy) I have to start from scratch. For a 3100 there are 4 cross members. The front cross member, the rear engine support, the second cross member and the rear cross member. In my previous post I said the second cross member but that was wrong. I should have said the transmission support or even a propeller shaft support. Attached are examples collected from searching.
Attachments
1949.jpg (37.82 KB, 107 downloads)
1950.jpg (192.5 KB, 103 downloads)
1951.jpg (46.29 KB, 103 downloads)
1953.jpg (80.75 KB, 108 downloads)
1954.jpg (297.17 KB, 107 downloads)

Last edited by buoymaker; 12/08/2020 9:06 PM.

"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."