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I was wondering what planning anyone else has done with their 4bts and a final drive ratio. I have a 4bt that I have planned for my cj7. I was reading about rpms and learned that somewhere between 1600 - 1900 is best at highway speed. Having chosen a 4bt for fuel economy and torque, I would like to maximize both. Here is what I have;
-jeep cj7
-4btA
-NV4500 (5th gear ratio .73)
-Dana 300 (1:1)
-axle ratio (not sure yet, might convert axles to 73-87 chevy 6bolt)
-thinking about 33 inch tires

Since the jeep will be driven mostly on the road, I thought about 33's because they would be a good compromise between the 235/75/15 tires that I have and the big stuff:) . I want to save fuel but dont want to lug the engine. I know about 4Lo's gear calculator and appreciate his site. I learned that with 3.73's I should rpm at 1800. Is this ideal, or should I go lower or higher? The vehicle is fairly light, so if I did go lower, I think the engine would still pull easily. Any opinions?
 

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According to the charts, the lowest BSFC is in the 1700-1800 rpm range. 1700 is lowest, so that would give you the best fuel economy. While still not getting fuel hungry if you should go 70-75. If you have the AMC 20 in your CJ that would be the next taller gear set...3.54
 
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