Okay i need some help! i have a 2009 JK i put a 4inch superlift on it and has 33inch tires.. Do i need to re-gear, will it help that much? is it worth the money?? I drove a jeep today with gears at 4.88 and i could feel a diff but i not sure if it is worth it.. as of right now i have 3.73... let me know what you think.. thanks!

I would think it would help quite a bit, you might get away with it depending on the type of driving/wheeling you do. If you go any bigger, it'll be a must.

Trans makes a big diff here, auto has .69 OD ratio while manny has .89 ratio.. rear ratio can help or hurt also, if you have 4.10 you'll be OK

On mine I don't use OD much unless I'm over 60 mph, don't like shifting in and out of OD mines auto w/3,73 gears, 32" tires

There are a couple of issues regarding re-gearing.

First 33s are not that big compared to stock. The difference between the two sizes of tires should have been difficult to detect.

The decision to re-gear is IMO one that has to do with the top end and bottom end of the forward gears. In first, torque is needed and sometimes slow movement is needed as in rock crawling and in first being able to do that very slowly without getting on the gas pedal. At the high end in 6th gear for standards and 4th gear for automatics, resides the economy of your drive train system. Re-gearing to a set of gears with a higher number, results in poorer fuel economy but gives the benefit of better torque possibly for towing in the highest gear.

Now comes purpose. If the jeep is going to be used on the trail a lot then re-gearing is high on the list of modifications. It is expensive to do this for only a little of getting off of the hard top. If the jeep is used mostly on the road and even for towing, when climbing hills, if there just isn't enough torque to maintain speed, more torque is always available by downshifting one gear. So you have to decide if the amount of off roading that you do is worth the price of the benefits received with re-gearing.

Im running a 2 inch lift with 33s and 3.73 gears with absolutly no problem

this isnt always true. if you're lugging it in OD, you're burning more fuel than if were running in the power band. im not saying 33"s/3.73 would or would not be lugging it, but lower gears does not automatically result in poorer fuel mileage

I got that information from the Jeep.com website paraphrased of course. They made a general statement about gearing and fuel economy. Lower gearing (higher number) = poorer fuel economy.

Generally speaking if you are lugging in a standard, your brain needs to communicate with the muscles in your hands and feet to accomplish a downshift. I have only found this necessary with towing but can see maybe if the tires are large enough or the hill steep enough that it may be necessary without towing. On an automatic, the gear choice is up the the brain in the car in the engine compartment (computer) and you would think that the engineers who programed it would have done so in a way that would have it downshift if it is "lugging it" as you say. BTW, this would be a good reason to have the speedometer re-calibrated after a substantial change in size of tires.

And yes, I agree with you about the 33s with the 3.73 gears not "lugging it".

thats true if you're talking a stock vehicle. but when you throw in lifts and bigger tires is when it gets more complicated.

the best example i can give is i had a 1/2 ton Ram with a 360 and some bolt on goodies. 3.55 gears/ auto. when i went to 33's it still ran ok down the highway. you lost some oopmf when you hit the hill country and it could downshift or whatever. but when i regeared to 4.10s, it ran in the heart of the power band, in od. my fuel economy actually went up both on the highway and in town. not by a ton, but a little. this was after i tried every performance mod i could afford to avoid regearing. in the end, deeper gears brought back the power, improved the MPG, and made it way more pleasent to drive. noone wants to spend the money to regear, then when they do they wished they did it sooner. just my $.02

Yah, I can see that with really big tires. Point made. But just think, after regearing substantially for those monsters, you then have to worry about axle breakage way out yonder. This jeep ownership thing is THE BEST because of all of the options but, MAN, hang onto your wallet!!!!! It is like a whirlwind. Sure can be exciting when the stuff arrives too....like Christmas!

With a manual tranny you can run 33's with 3.73 gears no problem, auto it pulls the engine down big time... I have one and run with OD off.

The difference lies in the OD ratios, Manual it's .89:1, auto it's .69:1... BIG difference and it takes the 3.8 way out of its power band

I can run in OD if I don't mind the trans downshifting all the time

My 2500hd has 3.73 gears running 35's, I can pull my GN full of cattle all day long in OD, in my allison trans OD is .72
Jeep has 3.73, 32's and it won't pull itself up a small incline in OD

The diff here is 450 ft.lbs tq vs. just over 200 in jeep... in a mag an unlimited was dyno'd and it pulled a massive 168 ft lbs at the rear wheels pathetic

its cliche but true "Just Empty Every Pocket"

soooooooooo.... what your telling me to do is turn off my OD?? correct? when i do that will it give me more power or what will it do?

I don't own an automatic so wasn't aware that there was an OD on/off control. I have seen and used this feature in other cars but not a jeep. I would think that in lieu of a gear change, this would be a way of putting your jeep back into the power band and into a more fuel conservative mode whilst going up steep inclines for jeeps with large tires. This is akin to downshifting in a standard. I would think that the effect on fuel economy would be the same as re-gearing. This is why I think that unless you have a real need for the uses for first gear in 4 low on the trail, if it were my own jeep with large tires, I would probably not re-gear unless it will be on the trail a lot. Without the gearing in first-4 low moving the tires slow enough to really crawl, it may be a bit more tricky to maneuver up difficult terrain. In this situation there is just no substitute for the correct crawl speed. I suppose, in a standard you could slip the clutch or in an automatic you could drive with your foot on the brake and gas at the same time if you only encounter it once in a while as a substitute for re-gearing but doing those things often will have an effect on the wear and tear of your transmission for an automatic and clutch for standard. Or you could just start off with a Rubicon....problem solved. Dang, so many choices. There's a jeep for everybody out there. Problem is, making up your mind about which one is right. And which mod to do and is it really necessary.

The problem with the fuel economy even with large tires, is that once you re-gear, your overdrive is over so to speak. So when traveling large distances and having the original gears would have meant better fuel economy on flat land or down hill on the highway, the choice is no longer there because of re-gearing. However, with the original gears the engine can be brought back into the power band by turning off O/D or downshifting. I guess this would be where I disagree with whitebuffalo.

what can i say, i speak from personal experience on several different vehicles. my YJ with 31"s and 4.10's couldn't get out of its own way. on 33s youd loose speed going downhill in 5th (OD). with 4.88s its no speed demon, but i can use all 5 gears, like you're supposed to be able to. its not just shifting the RPM range around, its also about the leverage to be able to turn the tires.

To the OP. you can get away without regearing. you will lose some power. it will be noticeable. if you can live with it, go with it. If you decide you want the power back: regear. like i said before, its expensive because its worth it

Did your YJ have an OD on/off feature where you could put the jeep back into the power band or are you saying that it had the feature and turning off OD it was still bogging down on inclines? If that be the case then it makes the argument to re-gear certainly. I guess if you can afford everything to have monster wheels, you should be able to afford the gears if that logic follows.

What was your experience regarding the above?

4th gear on a 5 speed manual is the same as locking out overdrive on the auto. you're running in direct (1:1).

honestly, regearing is going to make more of a difference going down the highway than it is offroad or around time. when you're in the high(er) gears is when the bigger tires zap the power

42RLE __________________AX5
* 1st - 2.84___________3.93
* 2nd - 1.57___________2.33
* 3rd - 1.00 ___________1.45
* 4th - 0.69 ___________1.00
* 5th- N/A ____________.85
* Rev - 2.21___________4.74

I'd have to agree with whitebuffalo here. With 33's and 3.73's you would even benefit from 4.10 gears, if economy is what you are after. Most just want to retain their power through all their gears and that is why we change the gears. It restores the jeep to the factory ratios that the engineers designed it to run at. Like said above its really noticeable in OD on the highway. But it is also a huge factor in low range on the trail. And that is why most of us bought these things, for the trail and not the economy.

You seem to have agreed with what I have been saying as well but I disagree with the part at the end of your post in red. I think there are a lot of folks out there who lift and purchase larger wheels without the intention of serious wheeling. That is where I differ with the re-gear at any cost mentality.

The post by jjacquin seems to point in that direction. You seem to be so focused on the trail that you can't see the need for mall crawlers at the opposite end of the spectrum who want the lifted, large tire, and mean look of the jeep without the desire to get the thing dirty. At some point between the two extremes, there is re-gearing. That takes some time and experience to determine if it is necessary. Some will re-gear and never or almost never use the capability. They will have wasted their money.

jk'n mine has literally been to the mall several times. But its happiest on the trail. I like good fuel economy as much as the next guy and can see both side of this conversation. I'm no hard core rock crawler, I can't afford to play that game. Even if I could I probablly wouldn't. I want a street-able jeep that I can explore the wilds in without breakage or problems. So I consider my self that guy in the middle of the spectrum. You are right these things can live in both worlds.

This is the BIGGEST difference between TJs and JKs. On my TJ I'm running 33" MT Baja Claw Radials, 4-speed auto, and 3.73 gears. My I6 makes more than enough grunt in the low end with the steep low gear that my 4-speed auto offers, all the while being able to maintain plenty of go at the top end for towing, etc.

Are 3.73 gears ideal for 33" tires? No. Does my engine lug because of it? Not really. Straight 6's make more usable low end power.

4point, I think we are identical on your thoughts in this quote. I haven't lifted and gone with larger tires YET but when I do, I plan to do more medium duty trails with my jeep club. I use mine as my DD so I have to be careful about how far down the trail modifications road that I go. I want to have fun with it off the beaten path and need to keep it in one piece for daily use. I have to control the jeep every time it sees a dirt road to keep it on course. I got yelled at this summer (for my almost volunteer job) because I got disabled on one of my many trips tearing through really rough back roads in New Hampshire just having loads of fun while on the clock going back and forth to the store(s) in various directions. Since I have the 4.0 gears in it if I do lift and go with larger tires, I will probably not be re-gearing but time will tell depending on how it responds on the trail. For me that is I bought it for is to have some serious fun with it. BTW, nice avatar with the wheel up like that. Mine goes to the mall a lot too! Cheers.