Busted rear diff dodge 2500

   / Busted rear diff dodge 2500 #51  
You have it correct, the higher number is better for towing and the lower number is for better fuel mileage.
 
   / Busted rear diff dodge 2500 #52  
As a rule of thumb, numerically higher lower gears will provide better fuel economy, but the selection of the "ideal" ratio depends on the torque curve of the engine, transmission final drive ratio (overdrive or not), anticipated load, and road speed while towing, among other things. In other words, it's possible to underdrive the engine by selecting too high a final drive ratio seeking better economy. Doing so might cause the engine to lug at cruising speed, increasing the possibility of both detonation and repetitive downshift-upshifting. You can also play with tire and wheel diameter to fine tune the rpms at cruise.
 
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   / Busted rear diff dodge 2500 #57  
Sometimes modern trucks will skimp on the size of the diff carrier to keep costs down and mileage up, at the cost of reliability. With a small carrier and a high (numerically)gear ratio (4:11 eg), the pinion diameter gets quite small and the contact patch is also small. You need a bigger carrier so your ring gear can be bigger and also your pinion diameter. But, they cost more and take more HP to turn those bigger bearings etc.

Edit: clarification.
 
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   / Busted rear diff dodge 2500 #58  
ruffdog said:
Sometimes modern trucks will skimp on the size of the diff carrier to keep costs down and mileage up, at the cost of reliability. With a small carrier and a high gear ratio (4:11 eg), the pinion diameter gets quite small and the contact patch is also small. You need a bigger carrier so your ring gear can be bigger and also your pinion diameter. But, they cost more and take more HP to turn those bigger bearings etc.
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Surely you meant "a low gear ratio", right?
 
   / Busted rear diff dodge 2500 #60  
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