To upgrade or not to upgrade, the question?

[DaddyO]

Confused to no end. Driving a 4-door ‘24 Badlands Sasquatch 2.7L with upgraded tires to 37’s, RC 2 1/2” lift with RC tie rod upgrade and track bar. Just received my Ford Procal to program the wheel sizes etc. I have a lot of gear and add ons including
Gobi roof rack
OpenRoad:
270 awning+sidewalls
12k hidden winch
Rooftop tent
Shower awning+water tank+water heater
Rhino:
Recovery boards
Tow ropes
Kinetic ropes
Soft shackles
Hard shackles
Tree savers
ARB onboard twin air pump
M2M tailgate table
Broaddict Molle panels
Pelican boxes
2 Jackery generators
Tools
And lots of stuff for traveling not listed.
I might add a cold air intake.

THE QUESTION: Should I upgrade my gears from 4.7 to 4.88s? Based on travel 65-70% highway and 30-35% offroad. I am getting mixed research recommendations. Currently getting 15-16mpg on longer highway trips of 300-600 miles. In town mileage is 12-13mpg. Did I miss anything?

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[Brian_B]

Should I upgrade my gears from 4.7 to 4.88s?

You would likely not even notice the difference, that's such a small bump.

What is the reason you are thinking of upgrading the gears? Mileage?

 

[ThunderFlash]

I'm no expert, but the mileage doesn't seem that bad to me considering your weight, the parasitic drag of all the external stuff, and turning 37" tires which got to be at least 15 pounds heavier per tire over the GYs, which is rotating mass.​

​

Did you correct the your odometer readings for the tire diameter difference? If not, it would be a wee little bit better.​

 

[brkdncr]

Best case, what improvement in mpg could you expect? When does the cost of the mod pay off in mpg savings?

 

[Colfaxent]

Best case, what improvement in mpg could you expect? When does the cost of the mod pay off in mpg savings?

Confused to no end. Driving a 4-door ‘24 Badlands Sasquatch 2.7L with upgraded tires to 37’s, RC 2 1/2” lift with RC tie rod upgrade and track bar. Just received my Ford Procal to program the wheel sizes etc. I have a lot of gear and add ons including
Gobi roof rack
OpenRoad:
270 awning+sidewalls
12k hidden winch
Rooftop tent
Shower awning+water tank+water heater
Rhino:
Recovery boards
Tow ropes
Kinetic ropes
Soft shackles
Hard shackles
Tree savers
ARB onboard twin air pump
M2M tailgate table
Broaddict Molle panels
Pelican boxes
2 Jackery generators
Tools
And lots of stuff for traveling not listed.
I might add a cold air intake.

THE QUESTION: Should I upgrade my gears from 4.7 to 4.88s? Based on travel 65-70% highway and 30-35% offroad. I am getting mixed research recommendations. Currently getting 15-16mpg on longer highway trips of 300-600 miles. In town mileage is 12-13mpg. Did I miss anything?

Wait and see what mileage you get after you correct the speedo.

 

[DaddyO]

I'm no expert, but the mileage doesn't seem that bad to me considering your weight, the parasitic drag of all the external stuff, and turning 37" tires which got to be at least 15 pounds heavier per tire over the GYs, which is rotating mass.​

​

Did you correct the your odometer readings for the tire diameter difference? If not, it would be a wee little bit better.​

Not yet. Just received the calibrater

 

[DaddyO]

Best case, what improvement in mpg could you expect? When does the cost of the mod pay off in mpg savings?

I was wondering that same question. I think the estimate is around $3000. I don’t think I’ll make up for it in my lifetime but will there be enough significant improvement to excite me? Offroad maybe more so.

 

[ThunderFlash]

If you get a good GPS speed or maybe use one of the digital roadside "YOUR SPEED" signs, you can figure how far off the speedo is. Convert that to a percentage, then multiply your milage by the result. So speedo says 60...GPS says 65. The larger diameter/circumference turns slower at same ground speed due to larger circumference, but time is the same regardless of tire. Then divide 65/60=1.083. With that, your 15.5 mpgs is more like 1.083 X 15.5 = 16.8 mpg. See, it's getting better!

I like the speedo method better than just using advertised tire diameters because it is a real reading off the truck and helps account for all the other tolerances and variables that might be in play.

Edit: also, as long as you're confident in your GPS/speedo readings, that same factor (1.083 in the example) should also be your increase to the tire size on the Procal or in FORscan. Estimating just using the nominal (but not accurate) diameters of 37" and 35", the factor will likely be in the 1.057 ball park. But I'm still on my stock tires and even so my speedo is off by about 3 mph as it is.

 

[CitrusBronco]

4.7 to 4.8, no chance, that is a waste of resources. If your changing gears go into the 5’s. At the size and weight of your rig chasing mpg gains is going to be marginal that you may never recover financially.

 

[Colfaxent]

4.7 to 4.88 is a rather small change, try some gear calculators it likely would be under a 200 rpm change. A relatively expensive mod for a small rpm difference. Plus your Bronco has 3 overdrives gears and so should hopefully be compensating for the 37s by not using the top gears as much (someone else can speak to that as I have a manual).

I'd go with 5.x diff gears if bothering to change, but it would be more for performance than mpg in your case. Personally I'd find ways to do what you want with less of that parasitic weight and unaerodynamic equipment. Your Bronco could very well be near 2000 lbs more than my Bronco, there is no free lunch all that fat changes the dynamics and mpg of a vehicle for the worse.

Good reccomendation here! Just put shifter in Sport mode and lock out higher overdriven gears to make up for the 4.7 ratio.

 

[Oldhippie]

If I was feeling “rich” I would go to 5.38s but really with an auto and 2.7 it probably wouldn’t be much of a noticeable change or pay for itself…I sure wouldn’t mess with going 4.88 or 5.13 over 4.7…

 

[DaddyO]

According to ChatGPT:

My Honest Recommendation For YOU

Because:

• You’re heavy
• You’re on 37s
• You drive 75 mph often
• You’re not going to 39s
• You’re not building a hardcore crawle

4.88 is the smarter choice.
It fixes the mechanical mismatch without overcorrectiing
If you were 50% off-road, I’d say 5.13.
But at 70–75% highway?
4.88 hits the sweet spot.


What 4.88 Will Do at 75–80 mph With your 2.7L:

Keep the engine in a better torque band
Reduce downshifts vs 4.70
Keep RPM moderate
Maintain good highway comfort
Improve off-road control noticeably
It will feel “corrected,” not aggressive.


What 5.13 Would Do at 75–80 mph
Strong off-road
Very responsive in town
Higher sustained RPM
Slight MPG drop vs 4.88
No real benefit unless you go heavier or larger tires

For someone cruising 65–70 mph? I’d lean 5.13.

For 80 mph? 4.88 is the better engineering balance.

 

[ThunderFlash]

For 80 mph? 4.88 is the better engineering balance.

If it was a matter of flipping a switch....or if you HAD to swap gearing because of a mechanical failure.....sure. But is the return on investment there to do it just because? As I was saying before, if you check your ACTUAL fuel milage based of the speedo/GPS readings, it's probably not that bad considering everything that has been done to the truck. I get 15 mpg around town in my 2-door 2.7L which is heavy for a 2-door, but probably still considerably lighter than yours....and I'm on the stock 35" GYs. It probably will not pay for itself....unless absolute OPTIMAL performance is the only goal. I personally believe you are in the realm of dimensioning returns on that 4.88 investment.

If you were REALLY over taxing the vehicle in some way, it would show up as excessive fuel consumption, which I don't believe you have. Laws of physics and thermodynamics are at work there.

 

[DaddyO]

Last trip from Austin south to Brownsville fighting a headwind it said I was getting 9mpg.

 

[Brian_B]

Last trip from Austin south to Brownsville fighting a headwind it said I was getting 9mpg.

Sounds normal for that rack and RTT

I went from 4.46 to 5.38. My MPG went from 320 miles per tank to … 325 miles per tank

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