Here are some details on the running engineering changes for these trucks.
"The cab itself, which had previously been attached to the frame at three points via shackle bolts and rubber mounts, was now mounted at four points. The idea of the three-point system was to let the frame flex without affecting the cab. This worked well, but the single forward mount put too much stress on the front frame cross-member, so two smaller shackle mounts were set on the forward chassis rails instead. The cab was still unaffected by frame flexing thanks to the lessened tension of the shackle bolts.
Frame flexing had caused other problems as well. There'd been complaints, for example, that the 1947-1948 radiator support in the 3100's tended to twist and shake loose after many miles on rough roads. This caused splits in the radiator core, and cracks in front-end sheet metal. For 1949, Chevrolet added X-bracing to the radiator support frame, reinforced the bottom channel, and mounted the entire assembly more rigidly.Hood shake had been another complaint, so a set of cross braces was installed. These ran diagonally across the inner front corners of the hood."
