4.10's to 3.73's

[aggoodin]

I have an 07 Extended Cab with a 2.3 auto. I use it as a commuter/occasional hauler. I drive 32 miles each way to work at 75mph on the cruise control. I am getting like 21mpg now that its cold out. I am disappointed. It turns about 3k rpm at that speed.

I was thinking about changing out the 4.10's to 3.73's to knock those RPM's down and get better mileage. My hangup is that the truck is going to have to work pretty hard to get up to speed with those gears and maybe negate the top end advantage.

Any thoughts on the subject?

 

[metalmacguyver]

in theory this would work. what you could do to see if you like it is put some larger tires on instead. it would have the same effect, wouldn't be permanent, and would be relatively cheap depending on where you get the tires. used tires from a tire shop would likely be free. just a thought.

 

[srteach]

I have an 07 Extended Cab with a 2.3 auto. I use it as a commuter/occasional hauler. I drive 32 miles each way to work at 75mph on the cruise control. I am getting like 21mpg now that its cold out. I am disappointed. It turns about 3k rpm at that speed.

I was thinking about changing out the 4.10's to 3.73's to knock those RPM's down and get better mileage. My hangup is that the truck is going to have to work pretty hard to get up to speed with those gears and maybe negate the top end advantage.

Any thoughts on the subject?

Not the best solution. 3.73's will cause more work for the engine. More work, more fuel use, especially if you have tall tires. I had a 96 2wd with a 5spd and it got about that mileage with properly sized tires.

You probably have some excess power that could turn taller tires. Metal gave the best advice, in my opinion.

 

[JFA_Spyderman]

To get the best mileage, the engine must be in it's powerband. And 3k is right about there. You will have to use more fuel with larger tires or higher (numerically lower) gears. And to be honest, 21mpg is about right for that truck.

 

[HAPPY_RANGER_GUY]

Slow down 5 mph and you'll see a difference perhaps. Slow down 10 and you'll certainly see a difference. This is your best option for better fuel economy.

T.

 

[jgrnot]

what you could do to see if you like it is put some larger tires on instead. it would have the same effect

I disagree. I put taller and wider tires on my truck. I can feel the engine working harder then it should.

Slow down 5 mph and you'll see a difference perhaps. Slow down 10 and you'll certainly see a difference. This is your best option for better fuel economy.

T.

I agree! I used to drive 70, 75, heck even 80! I used to get 220-260 miles on a 19.5 gallon tank.

Now that I drive 65, or whatever the limit is on whatever road I'm on, I get 300-340, on that same tank. IMO, that's a HUGE difference!!

Based on my 15-17 MPG (estimated, haven't actually checked in years), and current 87 octane in Reno priced at $3.35 per gallon, I'm saving around $15-$18 PER FILL UP by going 65 and not 75!

 

[metalmacguyver]

I disagree. I put taller and wider tires on my truck. I can feel the engine working harder then it should.

that is exactly what i said.

by lowering the gears like 4.10 to 3.73, the engine will have to work harder in the same way that it would have to work harder to turn a larger tire.

 

[aggoodin]

If I drive slower I have to leave for work early and at 70mph I'll get blown off the road by truckers non-stop.

Oh well I kind of felt I was stuck with what I have. Life served me lemons so I'll just pucker up and eat them.

 

[Bent Bolt]

I disagree. I put taller and wider tires on my truck. I can feel the engine working harder then it should.

A wider tire also increases the rolling resistance therefore uses more fuel. A taller narrow tire might have given you a better result.

 

[Bent Bolt]

If I drive slower I have to leave for work early and at 70mph I'll get blown off the road by truckers non-stop.

Oh well I kind of felt I was stuck with what I have. Life served me lemons so I'll just pucker up and eat them.

So let them blow by you. You don't know them and you get to keep more $$ in your pocket by driving slower.

 

[AllanD]

Taller gears at the same speed would probably make things worse.

3000rpm is close to the middle of the "sweet spot" for the DOHC 4cyl
and trust me you'd HATE it with 3.73's

Slow down a little.

Do consider slightly larger tires, the important thing is inflation pressure.

Rolling drag is more a function of tire deformation than of actual physical
size of the tire. tires that have mor eload capacity will deform less with
a given weight and so will roll easier.

Increasing your inflation pressure will reduce drag further.

You can actually inflate the tires to 10% over the listed maximum
inflation pressure and reduce drag even further.

this is about DRAG not traction.

Tires that are inherently stiffer, "LT" tires, Load Range C tires, Load Range D tires
or even "XL rated" P-metrics all allow greater load capacity via stronger, stiffer tire construction (less deformation thus less heat buildup) and if inflated to their max will reduce load capacity.

Larger tires will not necissarily cause more rolling drag, infact the opposite
is usually true, because the larger tire (presuming radial tires) will deform
less to carry a given weight.

To be honest a load range C 235/75-15 inflated to it's maximum pressure of 50psi
will roll significantly easier than a P235/75-15 at 35psi or 44psi (depending on the specific tire) and slightly less drag than even a 235/75-15XL rated tire at 50psi
because of the load range C's stiffer sidewall construction.

Load range D's operating at 65psi will reduce drag even further.
LT225/75-16 are not out of reason for a Ranger, even though
they are really made for an E250

But all this is only part of your problem.

Aerodynamic drag increases as a geometric function of speed.
and while in some cases running faster allows an engine to reach
a more efficient operating rpm if you are already running 3000rpm at your chosen speed with stock tires you are already there.

Infact running the same rpm with SMALLER tires at a lower speed OR numerically larger gears (4.56?) would probably gain you mpg because it would reduce the aerodynamic drag.

So try slowing down a bit, because switching gears probably won't accomplish
what you think it will.

AD

 

[aggoodin]

Allan, I feel like I should pay for a response like that.

 

[AllanD]

Glad you like it.

And if you want my paypal adress just ask

I do some rediculously LONG trips and some things that seem silly really add up...

but I have progressed from a 2.9 with 3.73's to a 4.0 with 4.10's

And my first "local driving" tank of gas with the 4.0 netted me better
mileage than I ever got doing the same type of driving with my 2.9.



AD

 

[jgrnot]

that is exactly what i said.

by lowering the gears like 4.10 to 3.73, the engine will have to work harder in the same way that it would have to work harder to turn a larger tire.

I was trying to say............I did that, and my mileage got worse.

A wider tire also increases the rolling resistance therefore uses more fuel. A taller narrow tire might have given you a better result.

IMO, I feel like it would get worse mileage either way.

 

[metalmacguyver]

I was trying to say............I did that, and my mileage got worse.

well every case is different.


none of it really matters though because the effect that stuff like this has on the MPG is pathetic compared to what effect the driving style has.