Medium duty engine/tranny?

To be a bit more specific, some also has to do with how long a motor will last before a complete rebuild. IE 400-600K miles vs 200K. BUT, still that is suspect in my mind, as Navistar had V8 diesel motors with equal mileage before rebuild as GM/Ford had the BB gas rigs back in the 90s, all had a 100K mile useage's. IE the IDI6.9/7.3 motors Navistar in mdt rigs, and Ford used in pickups and the SD350, before the current 450 chassis came out. My idi7.3 has 20 years and 140K, its on its last legs, but still usable. If one wanted a higher miles before rebuild, one went with a DT360/466/530 which had 400K lifetime expectancy if used city driving, 600K if more on the freeway. The T444E and subsequent 6.0, 6.4 V8's had 400K mile useages as the B5.9 and DT360 had. But lighter in weight, approx same hp for like useage.

But, I would agree with bedlam and some others, that it is not used as it should be per say by some forum members.

Marty