Rear Diff. Question for 3.73 ratio - Ford Powerstroke Diesel Forum
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Old 01-01-2012, 11:17 PM
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Talking Rear Diff. Question for 3.73 ratio

Hi guys,

I need to see about getting some lower gears for my diffs.

I run Toyo M/T's 38x15.5x20, with D1 (3.37) diff. gears.

What ratio would you guys recommend? (4.10, 4.30???)

I do a fair amount of towing, and this ratio, plus my large tire size, is KILLING my power!
She dogs on the bigger hills thats for sure.

Any and all opinions are welcomed.
Thanks guys.
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Old 01-03-2012, 07:19 PM
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Wow...

25 people have looked at this thread and NOBODY can give me a suggestion?!?!

Is anyone running a setup like mine?
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Old 01-05-2012, 05:29 PM
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Based on my Jeep experience this is what I see.

First tale a look at this. Gear Ratio from Tire Size

I am not sure what tire size your truck came with, so I guessed at 32" tall. Now running a 38" tire it looks like you should be running a 4.30 ratio.

Double check the numbers on the Currie Calculator.

Tom
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Old 01-05-2012, 05:37 PM
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4.30 would put you close to stock.
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Old 01-05-2012, 05:53 PM
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Quote:
Originally Posted by JSchuricht View Post
4.30 would put you close to stock.
That is the same I was thinking. It should be good. Just remember even if you go with 4.30s you still have a much bigger tire to get rolling and stop. It will never feel like it did stock.
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Old 01-05-2012, 11:09 PM
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I run 4.30's with my 35's and it works great.
4.10 is not worth going to because it is not much change from 3.73, so go to at least 4.30, or even 4.56 if you really want some good towing power!
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Old 01-06-2012, 11:14 AM
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Quote:
Originally Posted by GregsSD View Post
I run 4.30's with my 35's and it works great.
4.10 is not worth going to because it is not much change from 3.73, so go to at least 4.30, or even 4.56 if you really want some good towing power!
What kind of MPG do you get with the 4.30? I have a similar set up to the OP but have toyo All Terrains in a 37/14/18

As it is now i get roughly 14mpg. Mine doesn't struggle too bad in the uphills since i really don't tow more than like 7k but more power would not hurt. My truck only has a 4" turbo back and a k&n ram air intake as far as power mods go. Tuner is in the plans. Would it be best to get the tuner or the gearing first?

02 F250 7.3L 4x4
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Old 01-06-2012, 05:39 PM
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If you do the gears first, it will take alot of strain off of your tranny so it should last longer!

I get about 14 mpg, but I drive very little highway miles, it's all in town and backroads. Changing gears brought back about half the mileage that I lost by going to 35's.
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Old 01-06-2012, 08:23 PM
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Quote:
Originally Posted by GregsSD View Post
If you do the gears first, it will take alot of strain off of your tranny so it should last longer!

I get about 14 mpg, but I drive very little highway miles, it's all in town and backroads. Changing gears brought back about half the mileage that I lost by going to 35's.
If you don't mind me asking, what did it cost for the gears and installation for both differentials?
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Old 01-06-2012, 09:10 PM
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Originally Posted by z28gsxr View Post
If you don't mind me asking, what did it cost for the gears and installation for both differentials?

Gears, Bearings, and labor was around $1700-$1800
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