differential change

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Oct 22, 2013 | 05:13 PM

klr650goldwing

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Joined: Feb 2010

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differential change

If I change the 3:73 gearing on my 2004, f350 V10 4X4 to 4:30 or 4:56 what would the RPM be with each of those gears if I'm running stock tires?
Thanks.

Oct 22, 2013 | 06:41 PM

dkf

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Joined: Mar 2007

Posts: 10,101

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From: Pa

Stock tires, auto trans with TQ locked in OD.

4:30 @ 70mph : around 2275rpm
4.56 @ 70mph : around 2400rpm

http://www.grimmjeeper.com/gears.html

Oct 23, 2013 | 06:47 PM

PROSTOCK

Cargo Master

Joined: Feb 2004

Posts: 2,070

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From: Central Texas

Take your current RPM at any speed and multiply by 1.15 for 4.30's and 1.22 for the 4.56. It's a percent change.
Go 4.56, I just did 4.30's from 3.73 and am not impressed.