If you stay stock with the horsepower they will last a long time with regular service intervals. My friend has 3 Dodge cummins all autos. A 2000,2001 and 2003. They all pull 15k to 20k generators on a daily basis. The 2000 has 228,000mi and it is the original trans. The 2003 has 138,000 and no problems. Talk to allison owners and they will tell you the problems they have had,I think the Dodge transmission's are bullit proof untill you throw the horsepower and big time tourqe to them. By the way my buddy's 1995 cummins has 635,000 on her and still running strong with only one rear end and two manual transmission rebuilds. Gotta love that cummins we got.