Gearing/Gas milage issue. w/ SoCal location specific

[XJ96Classic]

Hey socal guys.. i posted a similar thread up in the modified tech forum.. but now i need some help..

96xj okay.. My rig is running 32x11.5 MTRS RE3.5 lift..8.28 rear end open. On the highway at 65-75mph i get 13-13.5 mpg at best. I have gotten as low as 12 on stop and go.

I use a gps to track my miles and i use the same pump at the same station to make sure its not a early cutoff station pump messing my results.

okay, so what gearing should i use? 4.10 or 4.56 Only catch is that i have a vision of running my stock tires when i have to take it cross country this summer. Would 4.56 be way overgeared for that?

I am looking for the best gas milage i can get. I had thought that having larger tires would make my rpms lower on stock gears and i would get okay milage at highway speed... but it seems i must be a little underpowered given the wind resistance and tire resistance and i am not running very efficiently.


SO FIRST OFF ... what kind of gas milage are you guys getting running similar tires to me and what gears are you using..


SECOND .... how hard is it to swap out and i would like some sort of limited slip set up or locker... should i just do it all at once? how long should i expect this to take... last.. lol anyone want to show me how to do it.

this is my DD and i would need to be in and out on the same day.

-THANKS you socal XJ guys are very helpful. Makes an CT guy have some fun living out here.

 

[XJ96Classic]

http://www.naxja.org/forum/showthread.php?t=940511


the other tread.. if you want to see the advice of the other people...

but i haven't heard enough to make a decision. . .

 

[Gerr]

for 32's id run 456's eventually youll get 33's anyways. running a stock tire with that gearing would suck though so maybe buy some new tires to put on after your trip.

Id do lockers at the same time as gears its gona save you money in labor

plan on a couple days for most shops BUT I have heard of a few same day guys on here talk to rawbrown

 

[Jump This]

As far as gas mileage goes, your just about right with the 12-14mpg.
At least that is what I was getting.
For your cross country trip, think about removing your front drive shaft, although I have never done this, it should help out a bit on the mileage.

My son's XJ has 4:56 with 33's and they work fine on the road...

 

[Kejtar]

Hey socal guys.. i posted a similar thread up in the modified tech forum.. but now i need some help..

96xj okay.. My rig is running 32x11.5 MTRS RE3.5 lift..8.28 rear end open. On the highway at 65-75mph i get 13-13.5 mpg at best. I have gotten as low as 12 on stop and go.

I use a gps to track my miles and i use the same pump at the same station to make sure its not a early cutoff station pump messing my results.

okay, so what gearing should i use? 4.10 or 4.56 Only catch is that i have a vision of running my stock tires when i have to take it cross country this summer. Would 4.56 be way overgeared for that?

Stock tires doing crosscountry trip? Not sure why you would want to do that. I drive once a year to Moab and I do it on whatever my rig has at the moment (last trip was on 35's).

I am looking for the best gas milage i can get. I had thought that having larger tires would make my rpms lower on stock gears and i would get okay milage at highway speed... but it seems i must be a little underpowered given the wind resistance and tire resistance and i am not running very efficiently.

Yup, resistance is what kills you.

SECOND .... how hard is it to swap out and i would like some sort of limited slip set up or locker... should i just do it all at once? how long should i expect this to take... last.. lol anyone want to show me how to do it.

My recommendation would be a locker like Detroit. Lunchbox lockers can be done later but you don't save that much as when you regear you'll have to buy a new carrier anyways. Add to that the cost of a lunchbox locker (it's the one that replaces your spider gears) and you have a detroit nearly paid for.

this is my DD and i would need to be in and out on the same day.

As I said before: show up to the M&G. One of the guys that's going to be there is a gear installer in HB and you can talk to him about timing and so on.

 

[Clean Racing]

Well once again I'll be the odd man out.. I ran 32's and 4.10's for 5 years as a daily driver, and trail rig. My scenario is a lot different from yours due to My jeep is a non HO (87~90 Renix version). I usually got 16~18 around town and as much as 22 on the hwy, not bad for an automatic. It is set up with 33's and 4.56's now and I can get no better than 16mpg before the motor swap. I have no record of MPG yet as I am still breaking in the stroker now only 350 miles on it. I have a buddy in Canada that has a 98 XJ 5spd with 33's and 4.10's. He was down for the holidays and told me he is getting 21 on the highway, he also drives like a grandma. You have to decide what your jeep is for, and how it is set up. So if you drive a ton of miles I would have to say 4.10's.. just my .02$ worth..

 

[Kejtar]

So if you drive a ton of miles I would have to say 4.10's.. just my .02$ worth..

Scott: I think when it comes to driving a ton of miles, not many get close to me and I still say 4.56

 

[XJ96Classic]

HAHA... looks like everyone has a different opinion on what to run.

Man I wish gas was 0.98 like when i first got my licence. I actually sold my 89 2dr. xj pioneer because i couldnt afford the gas back then...

I guess my next question would be.. do i need to get new gears.. or can i pick up a used set.... and anyone have a used ones lying around?

And.... what exactly would this do to my speedo? is there a speedomoter gear you can put in that compensates for both tire size and gearing?

does the computer need to know what gearing i am running for shift points on a automatic?

 

[Kejtar]

I guess my next question would be.. do i need to get new gears.. or can i pick up a used set.... and anyone have a used ones lying around?

With deepers gears folks usually sell the axle and the gears so you might shop around for that (removes the cost of install) though you might get lucky and find cheap gears. I prefer getting new gears myself.

And.... what exactly would this do to my speedo? is there a speedomoter gear you can put in that compensates for both tire size and gearing?

you'll just need to replace a $10 plastic speedo gear.

 

[xL8 APEKSx]

It sounds like you're OK on the mileage...these things are worse than V8's.

I'm getting about 230 miles per tank, 33's (A/T, Pro Comp, @ max PSI) and 3.55's. That's roughly 11.5mpg. Hard to tell though since the gas light comes on at 1/8 tank and even when the needle is into the "E" there's still a couple gallons left. I've never run it all the way to empty (stalling).

 

[Monkey55]

I think everyone has a valid point and you're right, everyone will have an opinion... some may be totally different and some may be the same..

First, I would slow down. 65-75mph is sucking at least 1 to 2 mpg's. Go 65mph and don't take off like a bat-out-of-hell. You'll notice a big difference.

I think Scott's 16 - 18 mpg's are definitely achievable with that setup. I'm getting about 15mpgs right now, but my rig is running rich and I haven't been able to figure out why yet.

Matching gear ratio to tire size to speedo gear is really key. 4:10's for 32's is a good match, but if you ever want to bump up to 33's (most people do) 4:56's would be better.

As far as running stock tires across country plus gears.. DOH.. You'd be geared way too low.

I used to have a set of street along with my MTR's and would swapped them out every time I wheeled and it was nice to have a quieter and smoother ride on the street. But, it became a hassle when I started wheeling about 1 to 2 times a month.

When it comes down to it, it's your decision what to run. You have to drive it. We're just suggesting what we think would be good. Everything is a trade off. If you go bigger & badder, then you'll sacrifice mpgs.

E