40” tires with 4:56 gears??

[Ytee]

Does anyone have any experience with 40” tires and 4:56 gear combo? Currently running 37” tires with stock 3/73 gears, get about 21-24 mpg with this combo. Also while towing a 3000# low profile trailer get about 17.5-18. Was trying to figure out how this would compare??
Thanks

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[Wheelin98TJ]

Here are a few ways to look at it comparatively:

37" to 40" is a 8.12% change.
3.73 to 4.56 is a 22.25% change.
3.73 with 37" tires is equivalent to 4.03 with 40" tires.
4.56 with 40" tires is equivalent to 4.22 with 37" tires.

 

[3VOLVE]

I just accomplished a cross country trip, totaling ~5700 miles, on 40’s and 4.56 gears. No trailer, but loaded down with Alu-Cab canopy, rooftop tent w/awning and Decked system. It performed well and I averaged 18.2 mpg going from sea level up to a hair over 13k ft.

The Gladiator moves out much faster than on the 3.73s, but still getting about the same milage.

Hope it helps.

 

[Ytee]

Thanks for the info!!

 

[Tennessee Gobi]

I have a 22 JTRD and I’m running 39” BFG KM3’s with 4.56 gears and it feels equal to stock tires and gearing. It pulls the same as it did stock (maybe slightly better), shifts about the same and still gets about the same fuel mileage as it did stock. I feel like it’s the perfect combination if you’re happy with stock performance.

I’m setup for Overlanding and the combination of the Diesel and gearing easily handles the weight when fully loaded.

 

[ATX_Jeeper]

I’ve had 4.56s with BFG 39s and now with MT 40s. It drives ok in the city but if you watch EGT, oil temp and calculated engine load % at highway speeds of 75+, you will see the engine struggle and use extra fuel (which soots the DPF and doesn’t burn it off and raises oil temp due to the engine load constantly being 85-100%). Because of this, I plan to re-gear again to 4.88 or maybe 5.13.

If I drop speed to 65-70, the soot % drops slightly during the drive. This happens with the stock tune and is worse with the banks derringer at any level other that stock. I do run the pedal monster on the city level 3-5 so that probably doesn’t help either.

I’ve witnessed this several times driving back and forth between Fort Worth and Austin. My build is light as you can see in my signature and only has 45k on the Odometer. Oil changed every 5-6k. MAF, MAP sensors cleaned about 10k ago. Air filter at that time as well. Tire pressure is good too.

Hope that helps.

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