The 2 speed rear has a low gear to get a load moving and a higher gear once you are rolling.I used to drive a C60 rollback tow truck with a 350 small block and a two speed usually drove it in high unless I had one one the bed and one on the wheel lift,or pulling a long grade you would sometimes split the top 2 to keep the rpm's up.They are nice when they work well but expensive to repair if abused.Onetunn
