any one running 4.56 or is everyone going 4.88. it looks like the 4.56 would be about 150 RPMs less which seems to be a good number for me. according to my calculations the 4.56s would rum 2625 RPM and the 4.88s would run 2815 based on my tires. im planning on ordering gears this week and looking for some guidence all i see is 4.88 and never 4.56 why is this
thanks for the help

 

I also like to see what others have to say about this. I will step up to 33" when the stock tires are worn, and I think 4.56 is a better setup for me than 4.88.

 

thats what im thinkin David at Northridge has the 4.56s in stock so i need some to chime in and help talk me into the 4.56s id go with 4.10s but dont know where to find them new.

 

4.88 would be OK for either 33" or 35" tires (although I went 5.13 for 35").
4.56 would be OK for 33", although I would go 4.88 for much better performance and minimal downside. If you have a long highway commute, don't tow much, and never plan to go bigger than 33" tires, I guess I could see the desire for 4.56.

Might be different for a manual trans, I have an automatic.
It it expensive, so get it right the first time.

Just my non-expert feelings after doing the research on my tire / gear combo. Use the search to find one of the hundreds of threads with the gear/tire size/ performance charts. Also, look for the charts that show Horsepower and torque at various RPM.
Try:
https://www.jk-forum.com/forums/show...ght=gear+chart

 

honestly, going 4.88 isn't all that bad and if you've got an auto, it's what i would recommend. the 4.56 is practically a waste especially if you already have 4.10's. as someone else mentioned, i went 5.13's with the 35's i was riding on and thought it was a perfect setup.

 

This is a great topic of conversation... My JK is a stock 2 door with automatic. It has the 3.73:1 ratio. I am currently running a 285x75x16 AT tire, that is not very aggessive. I drive on the highway... A LOT. I commute from Tampa to Miami at least once a month, and even though my JK has only been with me for a little over a month now, I already have 4500 miles on it, give or take.

I am ready for some more aggressive tires, and have been researching the combos out there. I think a 2 door looks fine with a 33x12x50 and a 2 inch lift. Just my opinion.

So, having said that, and only having a 3.73:1 ratio now... how would 4.88:1 effect rpm's with a 33x12.50?

At highway speed now, ~ 70-75 mph I am under 2K rpm... and I am getting about 19.4 mpg over the commute to Miami.

I'm not very worried about the fuel economy... or else I would have bought a Prius. I just wonder about livability?

With the limited off roading I do, plan to do... would 4.10:1, 4.56:1 or 4.88.1 be the best choice?

If I regear, I only want to do it once. I will add a locker up front and a posi in the back when it's apart.

Sorry to hijack the thread, but it's good conversation for a Newbie Jeeper.

Cheers!

 

I am in the same boat as you. I just use a stick shift instead of an auto. Running 3.21s. I do plan on getting 35s down the road, but it seems that 4.88 gears would have high RPMS and kill mileage with 35s and a stick.

 

I have 4.56 gears with 1" larger tires than yours. I also have a 4dr auto. My RPM is about 2250 at 70mph. I had 5.13 for a short while and I thought that was too low. Others like 5.13 just fine. I would have loved to see what 4.88 felt like but I'm not about to switch now. In town I have plenty of power and on the highway it's not bad. At 70mph I can hold and accelerate in 4th under small hills and when I kick down to pass I'm not red lining. The reason I don't like 5.13 is because I turn OD off when I tow my boat. IMO rpm is way to high in 3rd with 5.13 gears and my tires.

 

Running 4.56 gears with the 6spd. I would have to say this is the perfect setup with 35's and 6spd especially if you do alot of highway driving. This gearing is the most economical and is least likely to break by pinion gear failure being its bigger than 4.88, 5.13, and 5.38 More so driving at highway speed the RPM is like 2400 and at 80 mph its only at 3000 (ballpark figures for both) It has been said before that if you currently have 4.10 gears from factory you will have no problems with that gearing and 35's

 

If you want to know the effect of re-gearing, just take your current ratio, and divide it by the ratio you are considering.

For example, if you have 3.73's, and want to know what 4.88's will do:

3.73/4.88 = 0.764

1 - 0.764 = 0.236

To get percent, multiply that by 100

Or, it will RAISE your RPM, for any given speed or shift setting, by ~ 23.6%

So, if you used to cruise along at 2,000 rpm, you'll increase that to ~ 2,618 RPM with 4.88's.

If you try that for 5.13's, its going to RAISE your RPM by ~ 27.3% over the 3.73's, making that 2,000 RPM cruise jump up to ~ 2,751 RPM.

Of course, swapping on larger tires does the same thing as far as changing your RPM, except larger tires DROP your RPM.

If we assume that OEM is a 32" tire...

33's are going to drop your RPM by ~ 3%

35's are going to drop your RPM by ~ 8.6%

37's are going to drop your RPM by ~ 13.5%

As you can see, the GEARS are RAISING your RPM a LOT more than the tires are DROPPING your RPM.

This provides more torque, but, can make the engine wail at hwy speeds.

This is why people mention how much is TOO MUCH, as well as how much is ENOUGH.



As manuals and autmagic trannies have different final ratios, they don't work out to the same solutions.

As tires hit/pass the 35" mark, the rolling resistance grows much larger proportionally, and some extra torque is needed just to TURN the larger tires.

If you live where its hilly, and you don't like downshifting, etc...more torque than normal might be good for YOU getting through those mountains...but not so good for the guy in Kansas who has to drive past 100 miles of cornfields everyday....with the radio up to drown out the engine roar, etc.



If you look at the JK's torque band...and can see where in the RPM range it makes sense to try to be under YOUR driving conditions...you can figure out what diff gears might make sense.

For example, if the torque curve is flat along a section of the RPM band...more RPM still in that flat section, but not getting you more torque, will not help, just waste gas/make noise.