Ok I have read numerous "regearing" threads and was wondering why my JK is so sluggish(kicking out of OD,BAD MPG etc.) . I replaced my factory wheels and tires (255-75R18) with 33x12.5R15, they both measure 32 1/4" tall. Is it because the width of the tire. I forgot to say my JK is a 2dr auto w/4.10. I shouldn't have to regear because I didn't actually change the revolution of my tires. What else can i do? It just seems that every one that has had to regear changed the diameter of their tires. I don't know what route to go gears, flashpack. This is my DD so i need to get it back close to what it was. Any and all responses will be helpful. Thanks

 

Although the diameter/revolution may be the same or close...The new tire may just be heavier than your original. 4.10 should be ok for that size tire. I definitely would regear (that's just me as I am always looking for more UMMPHHH in the JK ). But the other alternative would be to get the Superchips Flashpaq. I have one and have no regrets with it. That may give back some driveability to your JK...

 

It's an Auto, sitting behind a weak engine. It's under-geared and under-powered from the factory. Turn O/D off around town, only use it when at cruising speeds.

Curious how you arrived at that. Mfg's specs? Side by side when off the vehicle? Both on the vehicle at normal inflation and load? I would be very surprised if the 33x12.50 isn't somewhere close to an inch taller. (my Nitto's measure 32" even when on my JK at normal psi and load. The stock sahara tires were noticeably shorter)

Anyway, do you have any intention of going to a taller tire? If so, re-gearing is definitely the way to go. If you are staying with 33's, give the Flashpaq a try before you jump into gears.

 

Don't try to fix gearing problems with engine mods. Regear first based on the gear charts and Torque vs RPM curves and then start your engine mods.

 

I agree with ntinhuf, likely your 'actual' dimensions are different...could be a heavier tire....but you didn't say whether you changed from an AT fully inflated to a MT with lower inflation...that'll definately increase your rolling resistance, causing many of your symptoms

 

33s with 4.10s doesn't need to be re-geared.

 

I did go from a AT to a MT both fully inflated. I measured them both off the rig and they both measured 32 1/4" tall. I wondered if the width didn't have something to with it. In the future I do plan on going bigger tire and bigger lift maybe I should just regear now. I plan on going 35's. I was just looking for a happy medium until then.

 

True, he just has 3.8Lvitis.

 

Here is some feedback from experience. I am running 33x13.5 LTBs which are heavy but the same approx diameter (my speedo is within 1 mph of GPS speed). Yes, the weight and rolling resistance makes a big difference, more than I expected as well. I can hold 60-65 on the freeway in O/D if I am lucky.

I have the flashpack and it makes it peppier around town, but doesn't help the highway that I have experienced. With the flashpack and O/D off, it works great but obviously the mileage goes down. I have 4:10's and plan to keep everything as is.

 

Thanks to all, I guess it is something that I am just going to have to live with it is a JEEP (wouldn't trade for anything tho) I will probibly check into a tranny cooler since I plan on taking road trips to Colo. and MO to do some real trail riding with it. There are none(trails) to really speak of in Iowa.