To me a big issue would be the Allison transmission. You need to take that critter on a 30 mile test run, up and down hills then travel a few miles in stop & go crawl. Look for delayed or hard shifts or ranging on grades where the transmission is having problems making up its mind which gear to be in.
I would have someone following looking for blue smoke any qty or blooms of black smoke when climbing hills and the Allison is ranging. Underneath look for fluid or fuel leaks. Check waterpump for leaks. Air brake time leakdown test then a 2nd time leakdown test with brakes applied. I own a bus with a 400 hp 855 Cummins. Hope this helps
