Yea you are right Ice Man. But GM does,t trust their 6 speed. The option list on a 6 speed GM DURAMAX is sad at best. While the CUMMINS 6 speed NV 5600 is a good tranny with all the options to be had. GM has the Dodge beat on the auto . But the CUMMINS has them beat on the 6 speed. WAKE up a bit GM. 310hp 590ftlbs is under 325 and 600.