awesomo

Will calibrating the speedo fix the tranny/shift hunt, with 3.73's?

fab1

I've been trying to decide also between 4.88or5.13s on my 2dr auto we play on a mix of rocks,mud,snow. One of my issue is to get to all the good places its like 4-5hr trip.putting in ARB lockers when I do the gears. So are the 4.88 that much stronger then 5.13s and can you really tell any different between the 2 when driving?

wayoflife

yes. an aev procal will help you to do this

4.88's are just a more stock like ratio for 35" tires. 5.13's will give you more power but, at highway speeds, your rpm's will be on the high side. if you're okay with that, it's kinda nice to have. regarding strength, in a dana 30, the pinion on a 5.13 will be quite small and, this will be a potential weak point.

fab1

That's why I was wondering if the 4.88 would be that much stronger to make worth giving up the little extra power of the 5.13s

wayoflife

eh, if you lock up your front axle and play really hard, it might make more sense to stick with 4.88's. but, if you go easy on the gas and keep your front end open, you'll most likely be okay even with 5.13's.

awesomo

Is there really a substantial difference if I lock both the front and rear, versus just the rear?

After reading this post, I think I've decided to go with 4.88's, since I don't really rock crawl that much, and really do more expedition stuff. I wanted to lock just the rear, to get additional traction, just for the little rock crawling that I do. Or should I do both?

yo_marc

Chiming in from the side here:

I'm a fuel-miser in my little Sahara... If there is one thing I was surprised about -- Higher RPM's dont necessarily mean worse mileage.

I get best mileage at 2,500 rpm's, right around 65-67mph. (4.10's on stock 32's would rock me 22mpg+ calculated). I wouldn't let them drop below 2,400rpm on the freeway; I could feel power drop off and I'd need more pedal to make it up hills.

I put on marginally larger tires recently; just enough to bump me out of that range. With the marginally taller height combined with the added weight, mileage is down - 18.x calculated and corrected on the last tank.

In short, I'd personally aim to have the motor buzzing above 2,500 at freeway speeds.

texwillys

I thought I'd throw this in: I'm running 34's on my JKU, auto tranny, 3.73's. I bought a Super Chips Flashpac and re-calibrated this past summer. It helped......some.
It won't make up for re-gearing, but I can get by while I save up for gears. My Jeep turns @1700 rpm at 70. I get between 17 and 18mpg on the highway w/o the AC.

EClass

I am running 285/75-17 with 4:10's. Cruise @70 around 2100rpm. When I need the extra on Hwy. it is sluggish. Also, between 60 and 70 it seems to want to up and down shift constantly like one said above...."struggle to find the right gear."

But, it's a Jeep and what I expected with mods. My '94 back in the day with 33's would barely do 70!! If I wanted smooth and fast, I would have bought a Cadillac.

Love my 285's BTW.

CMAN31

I have 4:88 with same size tires and love it. Get of the line and freeway speed at 70 to85 no problem even passing now is no problem. Getting around 16 to 17 in town as long as I stay off the floor board.