I've searched..., here, Naxja, JeepForum... some other homosectional (yes thats my word) places...

I need to settle this once and for all... I've been humming back and forth on the axle gearing issue for a long time now, was bored on my lunch at work so I started looking again...

Currently 3.55 with 31" tires.
I was thinking about stepping it up to 33's and figured I could deal with 4.10's until I drove a rig with that gear ratio and hated it, since it feels sluggish just like my XJ.

So I pretty much concluded that I wanted 4.56 as my axle gear ratio... if I stick with my plan of 33" tires. More recent information I stumbled upon, NOW people are suggesting 4.88's for 33" tires and 35" tires...

So now I'm stuck, I want to do this once... and only once.
Taking in account for added weight, rolling mass, aerodynamics etc... and running a 33" tire over multiple types of terrain... I'm fn' stuck.

What's holding me back is the highway commute to run rocks up in Northern Ontario. These trails are +4 hours away, I don't want my truck screaming at 4k RPM on the highway with an "assumed" 33" tire. I am currently running around the city with my 31's so running 4.56 or 4.88 probably won't be much of an issue for 70kph (max speed = 45mph)

One issue that scares me is the tiny bitch ass sized pinion of a 4.88 gear set. Cost isn't much of an issue at this point since I'm wanting to jump balls in right now.

HP D30, F8.8

edit: knowing I'll do something stupid... there is a high probability that I will eventually run 35" tires

FWIW... I run 4.56 gears with 37's on my 4.0/AW4 combo. In my opinion it does pretty good, but my engine ('92) has newer intake manifold, header, 2.5" exhaust all the way back, Rusty's intake... so that helps. It climbs grades at 55-60 in 3rd gear so I'm impressed with it. I don't feel I need deeper gearing when in low when running the Rubicon after an 8 hr drive there, although it wouldn't hurt :flipoff2: However, in the river bed low range is too low and high range isn't enough. When I ran 4.56 with 33's I hated it on the highway. With 35's it would be good.

I put 4:88's in the wifes and ran out on the hiway yesterday. 70 was turning 2700 with 35's. You need to pick your tire size first then gear accordingly. If you stay 33's 4:56 would be good, but not enough for 35's IMHO

With my 31's the 4.0 doesn't hold overdrive well at all with the 31's, so I drive around in third everywhere. At 100kph - highway limit in Ontario (let's just say 60mph for ease of calculation) in third it's at 2500rpm, which doesn't seem that great.... the sweet spot for me really seems like 2200 RPM, again not that big of a difference but I don't have to stab the throttle when it's cruising around 2200, and my speed is at around 85kph. Trying to reach 100kph, it feels like I have to drive the shit out of the Jeep spinning at 2500rpm :laughing:

Fawking gambles and compromises :shaking:

Cost doesn't matter? Get a tow rig :flipoff2:



But seriously, 4+ hours seems a bit much. You might could just get the gearing you want and put up with 1-2 hours but 4+ is a lot.

Another thought maybe to gear slightly towards highway driving (4:56 gears), then add a Tera 4 to 1 kit to the TC.

Memphis- I see you over in the hardcore forum alot so Im guessing you are doing some good trails.

Here's the thing, Since property is only something you read about where I live, I have never had space for a tow rig, trailer, rig etc... So all my jeeps over the years have been pulling DD duty, as well as hitting the red trails at rausch creek.

You have an auto, so you will need a bump deeper in gearing then I have done with my 5spds.

Ex-
I had an old XJ 4.0/ax15 with 31's and 3.55s, it was nice, I could wheel it decent as well as fly down the parkway. Since you have auto with the same gearing/tire it feels dogish, so your equivalent to that would be a 3.73 rear.

On that same truck I switched to 33's and 4.56's. I was in 5th by 50mph. The guys who live down the block from the trails would love this setup, but try driving that 4hours (like we have to) and you would hate it.

My current rig pulls 37's with a 4.0/ax15 and 4.56's. Now for most on here that is to high of a gear. However i cruise at 70 to rausch at a good rpm, and make up for it with a 4:1 case.

For you and 35's Id say 4.56, aluminum wheels to keep weight down, and a 4:1 or a 3speed xfer case.

Driving as far as we have to sucks, If Moab was in my backyard id be part of the 5.38 crowd.

Yea, lots of compromises... I am not hardcore by any means, however I do have some decent tech related questions. And usually post in hardcore because it's XJ specific... i.e. gearing with an AW4 is much different compared to an AX-15, nv3550 etc since that transmission is XJ specific... w/e it was moved yesterday. Thanks Ash.

4 hours is a sacrifice I have to make unless I want to run mud... and that's just blah :shaking:

I am running an np242 with the Go-Jeep slip yoke eliminator, so a 4:1 is out of the question since I love the full time 4x4 for the ridiculous weather conditions we have here in Ontario. Just had 15cm dumped on us!

Weight is definitely going to play a huge factor in my build up. So far the truck is basically stock, with the exception of the 4" lift with all the bells and whistles and my homemade bumper. My Cragar steelies weigh a heck of a lot of since they are so bloody thick.

Aluminum wheels are definitely on my mind for weight reduction, especially since I want to start my long arm cross member soon, and I need to build my frame stiffeners before I do that. Which is going to add a significant amount of needed structural support and weight.

i ran 4.56's, with 38.5's. also had a doubler with 4-1 in the 231. made up for alot. i ran a healthy stroker so freeway driving wasnt an issue either. i would sit at 1800 rpm's at about 70.

I run 4.88s and BFG AT 33s which are on the small side.

I do 65 right at 2500 rpms, speedo corrected and GPS verified. I never do more than 72-73 mph because at that point I'm at 2800 rpms.

How fast do you really need to go on the highway? 80+ mph? Fastest I ever really want is 75 mph.

I planned on 35s. With this setup, I calculated about 2500 rpms and 70 mph, and about 2700 rpms a little over 75. Sounds good to me.

Oh and btw I get anywhere from 15-17 calculated MPG.

So do whatever you want. I never plan to go faster than 75-80 mph, so 4.88s and 35s work fine for me. And don't be afraid to run the 4.0 to 2700 rpms while cruising, I do it everyday and mine doesn't give me one hiccup.