13 speed with brownie box?

If the 13 is an overdrive and you use a 1241a yes it will have 42 percent overdrive when using them both. But you better have a hoss to turn that kinda gear and more rotating mass. Also if that aux starts whining you better get it outta overdrive or you will regret it


If I wanted to go a little quicker I would just run my RPM on up higher. Unless the speed you want to run exceeds the engine RPM limit. There is no gain in fuel mileage etc. honestly I think it will be harder on the motor than just taching it out

 

Maybe I'm understanding the concept wrong would I have another set of gears when putting it in overdrive or would it be just one more gear

 

An RTLO 13 speed ends in .73 a 1241a has a final ratio of .85. So in 13 if you shift the aux into overdrive your gonna have .73 driving .85 so essentially another half gear up or close. The problem is it takes power to turn that auxiliary plus the percentage of overdrive it gets hard to do.

 

So I would probably be better off putting 4 elevens in my rear axles

 

Thing with gears is its give and take. Major gear reductions (like low and first) give you gobs of torque at a cost of speed. When you get into overdrives, its inverse: more speed at the cost of torque multiplication.

Too much overdrive might actually hurt economy if you have to keep your foot into it all day just to maintain the speed limit. Whereas running two or three hundred RPM higher with less overdrive might be more efficient since the engine doesn't need to work as hard.