Swapping up to the 4.10s

['22JTRD]

Pulled the trigger today and ordered the Spicer 4.10s from the gasser and Master Install kits.

Don't want to lose the top end highway mpgs that would come from upping to the 4.56s.

Since adding the Mopar 2" lift and going up to Nitto Ridge Grappler 38x11.50r17 last Saturday, I have felt the need to bring the power band back closer to oem spec.

The actual 37" tire on the truck dropped the ratio to 3.3 and effected what I feel is unacceptable fuel consumption at launch from stop.

I ran Nitto Trail Grappler 35x12.5x17 for the last 3 years and felt the 3.73 ( 3.55 due to 35" tire size ) was adequate since I don't tow and live in Flat Earth Florida

Tire Size Gear Calculator sez 4.22 to get back to oem spec, so it will end up being. 12 underdriven with 4.10s.

That small amount of underdrive should be acceptable at launch and give a fraction better highway mpgs.

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[Uparms]

I stick with 4.10s and 35s. If I was on 37, I would up to 4.56 or 4.88. Yes 3.6 8 speed.

 

[OldButStillJeeping]

If some of you haven't seen it....
Easy Peasy...

If you can't find 4.10, it's because 4.10 and 4.11 are basically the same.

If your Jeep came with 31s and 3.73, 2629 is your RPM. With 37s and 4.56 it would be 2693 RPM. A closer match. But to each his own preferrence.

 

['22JTRD]

I stick with 4.10s and 35s. If I was on 37, I would uo to 4.56 or 4.88. I

I'm guessing that yours is a 3.6 gasser. Mine is the 3.0 EcoDiesel

Calculations tell me to go to 4.22 to return to oem spec

 

['22JTRD]

If some of you haven't seen it....
Easy Peasy...

This doesn't apply to the Diesel

If some of you haven't seen it....
Easy Peasy...

That doesn't apply to the Diesel

 

[OldButStillJeeping]

It is not engine specific. Diesel, gas or hyper drive. It's tire, R&P, and RPM calculation. Has nothing to do with engine type.
You match RPM in the chart as a baseline for R&P and tires calculation. Not what your actual diesel RPM is.

In fact, that chart is from a diesel website:
https://pspdiesel.com/re-gearing-when-is-the-right-time/

 

['22JTRD]

It is not engine specific. Diesel, gas or hyper drive. It's tire, R&P, and RPM calculation. Has nothing to do with engine type.
You match RPM.

Your logic is disregarding that the Diesel and gas engines have entirely different rpm power specs

I size ratio doesn't serve both

 

[OldButStillJeeping]

Your logic is disregarding that the Diesel and gas engines have entirely different rpm power specs

I size ratio doesn't serve both

In fact, that chart is from a diesel website:
https://pspdiesel.com/re-gearing-when-is-the-right-time/

 

[fourfa]

The diesel engine redline is 4500 rpm. Pentastar redline is 6500. The obvious implication for gearing calculation is best left as an exercise for the reader

 

[OldButStillJeeping]

But diesel or gas doesn't matter. RPM in the chart isn't your engine, or any engine.... It is a tire size to R&P chart. You put in your original tire size and R&P. Then match the RPM in the chart to what Tire you are changing to.

 

[OldButStillJeeping]

Sorry brothers. Respectfully, You are not understanding it.

Redline, idle, etc, etc doesn't matter. It is about matching stock final drive ratio.

Do what you want.

 

[Ericshere03]

Pulled the trigger today and ordered the Spicer 4.10s from the gasser and Master Install kits.

Don't want to lose the top end highway mpgs that would come from upping to the 4.56s.

Since adding the Mopar 2" lift and going up to Nitto Ridge Grappler 38x11.50r17 last Saturday, I have felt the need to bring the power band back closer to oem spec.

The actual 37" tire on the truck dropped the ratio to 3.3 and effected what I feel is unacceptable fuel consumption at launch from stop.

I ran Nitto Trail Grappler 35x12.5x17 for the last 3 years and felt the 3.73 ( 3.55 due to 35" tire size ) was adequate since I don't tow and live in Flat Earth Florida

Tire Size Gear Calculator sez 4.22 to get back to oem spec, so it will end up being. 12 underdriven with 4.10s.

That small amount of underdrive should be acceptable at launch and give a fraction better highway mpgs.

You say that 3.3 effective ratio is unacceptable for fuel consumption… I’ll add that a ram truck ecodiesel comes with 3.21 and tows up to 8k miles …

I personally want to go 4.56 with my 37’s but my MPG SKYROCKETED after going to 37’s and I can still tow my travel trailer with ease …

stock rubicon ecodiesel (2023h was struggling to get 21mpg on the highway. Added a stage 1 tune from EOC and it bumped up to 24mpg. Upgraded to 37” KO2’s and I can flirt with 30mpg (no lift). If I drive normally not caring about MOG and mixing city with highway I’m at 27mpg.

AMAZED… and this is my SECOND ecodiesel gladiator.

I do want a lift, but so far my relatively small KO2 37’s do not rub, front or back. Remember us ecodiesel have longer front bumpstops. I only want to add a lift for stiffer springs and shocks because stock rids like a marshmallow and add more uptravel so I can go over speed bumps without coming close to a full stop first.

 

['22JTRD]

You say that 3.3 effective ratio is unacceptable for fuel consumption… I’ll add that a ram truck ecodiesel comes with 3.21 and tows up to 8k miles …

I personally want to go 4.56 with my 37’s but my MPG SKYROCKETED after going to 37’s and I can still tow my travel trailer with ease …

stock rubicon ecodiesel (2023h was struggling to get 21mpg on the highway. Added a stage 1 tune from EOC and it bumped up to 24mpg. Upgraded to 37” KO2’s and I can flirt with 30mpg (no lift). If I drive normally not caring about MOG and mixing city with highway I’m at 27mpg.

AMAZED… and this is my SECOND ecodiesel gladiator.

I do want a lift, but so far my relatively small KO2 37’s do not rub, front or back. Remember us ecodiesel have longer front bumpstops. I only want to add a lift for stiffer springs and shocks because stock rids like a marshmallow and add more uptravel so I can go over speed bumps without coming close to a full stop first.

Right now with the 3.73 and 38s, it spends too much time in the lower gears of the tranny getting up to speed.

I have already flashed the ecm with the measured 37" tire size.

It gets 30 / 32 mpg at 55/60 mph on the 38s on flat ground here.

I was getting 20mpg at 75 mph with the 35s I was running with an effective ratio of 3.55.

 

[Tulbox]

I have a diesel also and the chart must take into count for the trans, manual or auto or the speed you going at the RPM. Otherwise the chart is bogus. My diesel with 3.73 and stock 33: tires turns 1600 RPMs at 60 MPH with the auto in 8th gear.

 

[Tulbox]

I stand corrected, on looking at the website that chart does indicate it is based on 65 mph, but still our trans are completely diff. So if I am out of overdrive of 8th gear and in 7th which should be close to the 1:1 I am still only doing about 1900 at 65mph. One still needs to know more information and one chart is not good for all vehicles.

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