Why diesels are most efficient around 1,800 rpm

ShinerBock wrote:
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Manufacturers do not make different trans tunes for different rear gear ratios. YOU are suppose to pick the rear gear ratio that has the best blend of of efficiency/performance based on how you use your truck.

Drivers can create their own transmission tune with a little click when the situation requires it. Selecting 7 instead of 8 when approaching a hill has the same effect as changing rear axle ratios and a whole lot cheaper and easier.