Rear end ratio
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New User
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Rear end ratio
Has anyone gone from a 3.73 to a 3.55 and gained what in mpg?
Observed what in rpm drop
2000 PSD CC SB 2WD AUTO 3.7 150K ITP Reg. Rtrn,AFE,Magnaflow3.5dp/4back
foil delete,zoodad mod,hp oilxvr, .450 sonnax mod, DP 80e 80t F5, autometer pyro,boost
Thanks
Tom
Observed what in rpm drop
2000 PSD CC SB 2WD AUTO 3.7 150K ITP Reg. Rtrn,AFE,Magnaflow3.5dp/4back
foil delete,zoodad mod,hp oilxvr, .450 sonnax mod, DP 80e 80t F5, autometer pyro,boost
Thanks
Tom
Fleet Mechanic
Joined: Jul 2005
Posts: 1,800
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From: Southern Colorado
You can just do the math as a straight percentage for the RPM, but IMO, that's not enough gearing change to bother. If you bought 1-2 sizes bigger tires, you can turn 3.73 into 3.55. These trucks are a giant physics problem (as far as fuel economy) and a few RPM just won't change it enough to bother. If you went from say, 3.73 to 3.08, then you'd see a significant difference.
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,695
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From: SE Florida
You'll drop 4.8% in RPM. So if you now are at 2000 RPM if you change to 3.55 gears at the same speed you will be turning 1900 RPM. You might be able to gain tenth of a MPG, maybe not.
Cargo Master
Joined: Oct 2011
Posts: 2,862
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From: SoCal/Wyoming
You can have some benefit but that would depend on the type of driving you do. I run 37” tires with stock 3.73 gears which puts me in the 3.50 range. While I gain a little mileage on the highway, I lose a little in town. Since everywhere I drive from home is highway, it works for me but if I used my truck for mostly towing or in-town driving, I would change the gears. Here is what my RPMs look like at 65mph.<O
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New User
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Rear end ratio
Thanks for inputs
I guess even if I got 1mpg I would have to drive many miles to pay off those new gears
Then again with taller tires you'll be higher in the air which will cause more drag
I guess even if I got 1mpg I would have to drive many miles to pay off those new gears
Then again with taller tires you'll be higher in the air which will cause more drag
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