Time to regear the JK 4.56 vs 4.88

[MuleShoer]

The JKU is equiped with ARB bumpers, winch, hardtop, full rack, and 33 in tires ( actually they are 285-70X17" so not quite 33")
I drive 80 miles / day on the interstate, things were ok unitil I added the rack, now th JK can't get out of its own way.
Since a diesel conversation has not materialized so I am going the regear route.
This is an automatic with 4.10 gearing. on a one for one basis 4.56 gearing would bring back operating rpm to stock , roughly 2150rpm @ 70mph
My concern is not many people use 4.56 gears instead they go with 4.88's
WHY?
Also I plan on towing a Conqueror Compact out to Chaco canyon in June so the mileage performance is a big concern on a 3000 mile trip

Thoughts

[leman]

if your gonna be towing i would go ahead with the 4.88, but thats just me.

im running 35"s with the 3.72 gears and had a rack on there for awhile. when i regear im going to 5.13s

[ROKTAXI]

I've been running 4.88's for about 3 years now. Although it's not my DD, it still behaves well on the highway (fuel mileage). I'm running 33's, auto trans. RPM's are about 2300 @ ~65 mph. I rarely do 70.

I don't think you'll get much, if any, negative input from those that have changed to 4.88's.

[MuleShoer]

I've been running 4.88's for about 3 years now. Although it's not my DD, it still behaves well on the highway (fuel mileage). I'm running 33's, auto trans. RPM's are about 2300 @ ~65 mph. I rarely do 70.

I don't think you'll get much, if any, negative input from those that have changed to 4.88's.

Things were OK until the kicked the interstate speed to 70 now I have trucks climbing up my spare tire

What kinda of fuel mileage you getting?

[ROKTAXI]

What kinda of fuel mileage you getting?

+ / - 16mpg

130K

[ssmathis]

I had a similar setup and went with 5.13 gears but I live at over 6000 feet. I was running 2800 rpm's at 75 out here in Colorado.

Scott

[Hilldweller]

I have 4.56 gears, 285/75-16 tires, an automatic, and tow a Conqueror Compact. If I could do it again, I'd have 4.88s.

I live in a hilly area and the gears are fine (after using the Superchips Flashpaq) until I hitch up the trailer; then it dogs-down on the hills something awful.

Fuel economy? Forget it. 15-18 without the trailer; 14-ish with the trailer.
We pulled it from N. Georgia to S. Arizona on our longest trip; about 11,000 miles of towing it so far.

I have a 2-door that had the second softest springs. Added bumpers & winch ---- that made it sag and wallow. Switched the springs to the stiffest OE, donated from an Unlimited/tow package. Then added a Teraflex 2.5" puck lift with shocks on top of that.
It rides much better than stock.

Do yourself a favor and add another trans cooler before you tow.

http://img.photobucket.com/albums/v352/billpearlman/068_crop.jpg

[Scott Brady]

Go as low as you dare. I would go 5.13s with that motor. We have 4.88 in the OVJK and it is adequate.

[Hilldweller]

Go as low as you dare. I would go 5.13s with that motor. We have 4.88 in the OVJK and it is adequate.
Don't you have 35s on it now though?

[Scott Brady]

It does have 35s.

I would love it to have 5.13s

I had 5.29s in the Tacoma with 34s and it was juuuuuust right :D

[Hilldweller]

It does have 35s.

I would love it to have 5.13s

I had 5.29s in the Tacoma with 34s and it was juuuuuust right :DDude, drive one with 35s and 5.38s; you'll really like that.

[alosix]

I went through a similar dilema with my TJ when it was running 4.10s and 35s. It badly needed more gear.

After doing the math on both, 4.56 just didn't seem to be enough of a change to warrant the work. Ended p with 4.88s. Jeep much happier. I know, diff engine, diff Jeep. But, if you're unhappy with 4.10, I don't think 4.56 is enough of a change to make it better.

Jason

[MuleShoer]

[QUOTE=Hilldweller;805949]I have 4.56 gears, 285/75-16 tires, an automatic, and tow a Conqueror Compact. If I could do it again, I'd have 4.88s.



I went with OME springs and the improvement was great. roger the trans cooler..Oh and Conqueror used to be Chips.

All the comments/ suggestions, both here and on the JK site have been..4.88 or 5.13... going to 5.13's makes me very nervous:confused:
My concerns are when I am in some serious mountains and I come out of OD, ouch. I have a couple weeks before I drop the cash but today I am thinking 4.88's now.

Hope to come down for the Eastern EXPO if they settle on a date, I leave for Chaco June 10th

[alosix]

My concerns are when I am in some serious mountains and I come out of OD, ouch. I have a couple weeks before I drop the cash but today I am thinking 4.88's now.

If you're in serious mountains you probably don't want to be going up it trying to do the speed limit with trailer in tow most of the time. Looks like the Hemi JKs can do it, but if you're going up something with 4.88s or 5.13s that is too much for OD you'll prob be crawling up it anyway trying not to cook it :)

The only question to ask yourself at this point is are there bigger tires in your future. If they are, 5.13s might be the ticket.

[MuleShoer]

IfThe only question to ask yourself at this point is are there bigger tires in your future. If they are, 5.13s might be the ticket.


today no but in two years when I replace them I just might go up to 34's (315/70X17) but thats a long way off so I will worry about it then

4.88's are planned once my lockers show up

Thanks

[Hilldweller]

Oh and Conqueror used to be Chips.

Hope to come down for the Eastern EXPO if they settle on a date, I leave for Chaco June 10thYou're going to have a great time; that trailer has good karma all over it.

http://img.photobucket.com/albums/v352/billpearlman/100_2905.jpg

Think about a Superchips tune also; made my Jeep much easier to live with.

[thewas4x]

The 3.8L V6 really is happier with lower gears. Completely different powerband than the old inline 4.0L. And the 3.8L is much smoother and still relatively quiet at 3000 RPM+. I strongly recommend the 4.88's. I have driven auomatic JKs with 35's and 3.73's, 4.11's, and 5.13's. 5.13's were great all around, and for comparison, I have driven one on 37's with 5.13s. Also drove a 6-speed where we installed 35's and 5.88's. Your setup would benefit most from the 4.88's. With the auto, you are impacting your acceleration and performance throughout the engine's powerband, not just the final drive. Were in a manual you can have an impact buy changing your shifting pattern.

Chris

[Morticon]

To me your gearing really depends on the TRUE measurements of your tires. wait until you have them on your jeep and see what they are. I have 35's but after about 40,000 kilometers they are measuring out at 32.75"

with 5.13s and barely 33" tires your gas mileage is really gunna suffer. 1st gear is pretty much useless, i barely use it unless starting on a hill.

I have a 2dr so i have a 60 litre tank and around town 0 highway im lucky to get 300kms to the tank.

on the highway closer to 450 or 500 depending on if im driving into a lot of wind or not.

if you are going to get 5.13s make sure the true measurements of your tires are as close to 35 as possible.

Mickey Thompsons are notriously bad for saying 35 but barely being 34

some good tires for acurate tire measurements are toyo open country mts as well as the goodyear mtrs with kevlar.

but then again its your jeep do what you want!:smiley_drive:

[Stumpalump]

I never hear I wish I gone with a higer gear set but often hear I should have gone lower. With that said 4:88's are as low as you can go on a Dana 44 befor you comprimise strength of the ring and pinion. After 4:88 the pinion gets tiny. 4:56 gears would be as low as you should go if you had a Dana 30 up front FWIW. An easy way to remember is to look and see the lowest gear set Dana Spicer makes. They won't make anything lower than a 4:88 for a Dana 44 or a 4:56 for a Dana 30 because they are weak. I know you have 44's but I'm just saying. Another thing that you rarly hear and most don't know is who makes the best, stongest, longest lasting and easiest to set up ring and pinion gears. That would be Dana Spicer on Dana axles. They are hands down the best. On the popular to swap Ford 8.8 rear it would be Ford motorsports gears. In a lot of cases you can just bolt them in and go without changing shims. The setup will be that close. Good luck on your choice. You have to decide do I want best power and performance (4:88) or do you want to squeeze that last MPG out with the 4:56 on your freeway drive. You live in mountains. Thinner air make s less HP and the hills bog it down . Go 4:88's.

[MuleShoer]

I never hear I wish I gone with a higer gear set but often hear I should have gone lower. .....best power and performance (4:88) or do you want to squeeze that last MPG out with the 4:56 on your freeway drive. You live in mountains. Thinner air make s less HP and the hills bog it down . Go 4:88's.

Stump
Maybe thats my problem the thinner air:sombrero:
Here in SW virginia we are at the 2500-3500 foot level whic is nothing compared to out west.
Becausing of the need to tow our trailer I think I am going with 4.88's, I hear the Yukon Gears are pretty decent
Thanks

[Vincent]

I recommend the 4.88 for the manual, and 5.13 for an auto. I have the 4.88's @ 6-speed w/ 33's, and couldn't be happier. Note, that 4.56 are really hard to find, even if your favorite catalogs show them, nevertheless, i wouldn't go 4.56, especially w/ an auto and tons of hardware leeching on you for wind drag. Good luck!

[CGwelder]

Look at it this way, there is very little change from 4.10 to 4.56, period. My Rubicon is a dog with 4.10 gears and stock tires, the thing that helps the most is that it's a manual. If I were you I would be thinking 4.88 or 5.13, and a heavy duty trans cooler with it's own electric fan. Nothing ruins your day like a fried transmission. I had 4.88's in my CJ on 35's and it ran great but I could not imagine towing with it.