We have a 40ft Tuscany with the 6.7l Cummins and Allison transmission, only problems was going west out of Denver speed got down to 30mph.
But a lot of power issues isn’t the engine or transmission but the programming of them, almost all of these are programmed for best fuel economy.
What I did was change my cruise control setting from a hard cruise to soft cruise, changed transmission setting to performance, haven’t been back through Denver since then but from Ohio to Florida with the cruise set at 70mph it never drops more then 5 mph.
Soft cruise is basically all throttle to power up hills, hard cruise let’s the ecm increase the hp to maintain speed, and with transmission set up for performance mode just doesn’t shift up as quick.
You have to have a computer with Cummins in-site and the Allison software to make these changes.
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