Hey Brandon,
As 3B said, Chevrolet started producing factory tandems for the 1956 model year and were available on the 10000 series trucks. In 1957 they also became available on the 8000 series trucks. They used a pair of 15,000 pound Chevrolet rears with a 3-speed power divider. The power divider had two "underdrive" gears (2.22:1 and 1.22:1) and direct. The power divider also allowed the operator to switch from dual drive axles to single drive on the fly. The rears could be either 6.17:1 or 7.20:1 ratio. The transmission could be either the Spicer 5-speed or the 6-speed Powermatic. Power steering and a 4-barrel carburator was also required equipment.
I have seen a picture of a 8000 series 1957 and I have seen in person 2 different 10000 series units...not to many of them around.
FYI, my information only covers the Task Force trucks 1955 thru 1959.
Mike B
