Rear end
 

I bought a Eaton posi for my 3.25 rear end. I have a 700r4 transmission and so I I would like different gears. I thought I read when I bought it that the lowest gears I could put was a 3.42, but could I put 3.73s? I can currently go 100mph and I’m only pushing 2500 rpm, which is where my cam is just starting to be happy and I know if I can get lower gears I could get better fuel mileage. Currently getting 13.7mpg on the interstate at 80-85 mph. Or do you think 3.42 would be enough. I have a blueprint high performance 383 roller engine.

Re: Rear end
 

I would go with 3.73’s personally, you’ll appreciate the low end power it will produce. If you don’t wanna go that low, I would then consider 3.55’s. That would be a happy medium of low end and freeway speeds with the 700R4.

Re: Rear end
 

Will a 3.73 fit on my carrier?

Re: Rear end
 

You didn't mention what rear end you have , if it's a truck 12-bolt, then with 3.25 gears you would have a series-3 carrier. You can get "thick" 3:73 ring gears, that fit a series-3, you can also get 4:11, maybe even lower. I personally would go with 4:11's.

Re: Rear end
 

Sorry yes I have a 12 bolt. I don’t really want 4.11s it has enough power with my 3.25, 3.73 I feel would be plenty. I’m just wanting it to be a better cruiser on the highway and interstate.
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Re: Rear end
 

bbc=>700r4=>3.73 ( about +9 on the ODO here )

Re: Rear end
 

12 bolt truck carrier is 2.76-3.42 and 3.73 up. So you will have to do something different.

12 bolt car carrier brake is a total different animal.

http://www.differentials.com/technic...arrier-breaks/

Re: Rear end