paging dr. hornbrod, and others who feel like chiming in..

[mvusse]

WIth the AW4, 4.10 would be great. For the AX15, I fear it may be a bit high, but I say try it and see how it goes. If nothing else, just skip 1st.

 

 

that math computes to the gearing actually being a little low.

 

 

Correct. High number ratio = geared low.

[fiatslug87]

It's here Fiat: http://www.jeepstrokers.com/forum/viewtopic.php?f=5&t=387

Very nice!!!

[JeepcoMJ]

that said, I was using a figure of speech when I said "redline". what I should have said is that I don't feel like running @#$% ridiculous high rpm's at constant. I like gas mileage...it doesn't need to hit 3,000 rpm at a constant.

If I were a betting man, I would be willing to bet that with two otherwise identical MJs, one that ran 3,000 RPM at 70 MPH would deliver better gas mileage than one with stock gears and a 5-speed, that runs 1960 RPM at 70 MPH. There's just nothing like running UNDER the torque curve to boost your gas mileage ... NOT.

 

3,000 RPM is not "@#$% ridiculous high rpm's" for these engines -- it's the speed they were designed to run at.

 

 

it's torque curve is 2250. keep it around there, you're good. I don't want to get it much higher than that.

[Eagle]

it's torque curve is 2250. keep it around there, you're good. I don't want to get it much higher than that.

Correction: Its torque PEAK is 2250 RPM. The torque curve below that is ramping up, while beyond that it's pretty flat all the way to about 4,000 RPM. At highway speeds, when you're pushing that flying brick through the headwind, you'll get better gas mileage running 2500 to 2600 RPM than you will running 1700 to 1800 RPM.

 

As I wrote, the basic engine was designed to run all day at 3,000 RPM. Aside from EFI, the only basic difference in any of these engines, all the way from the original 232 c.i.d. to the 199 to the 258 (4.2L) to the 4.0L is the stroke. The 4.0L is the only one that used a different bore, and it's not different enough to affect reliability at a sustained 3,000 RPM cruise.

[JeepcoMJ]

I stand corrected.

 

 

what I should have said, is that the torque curve and hp curve meet at roughly 2250rpm.

 

 

 

 

either way eagle, you can argue with me all day....there is NO WAY ON EARTH that I want to run any engine, of any make, model, or type at 3,000 rpm constant.

 

 

I didn't even like running my 2.5 that high...and it literally needs to run 3350rpm to maintain speed on the interstate with 4.10's and 5 speed.

[Geonovast]

I've run my 2.5 at 3400-3600 constantly for 9ish hours straight several times and it never once had a problem with it. :dunno:

[Eagle]

I didn't even like running my 2.5 that high...and it literally needs to run 3350rpm to maintain speed on the interstate with 4.10's and 5 speed.

I don't know how fast you drive, but even with 205/75 tires and 4.10 gears 70 MPH would only be turning 2750 RPM. 3350 would be an 85 MPH cruise. Personally, I wouldn't drive any MJ (or XJ) that fast, even if it were legal (which, of course, it isn't).

[JeepcoMJ]

I didn't even like running my 2.5 that high...and it literally needs to run 3350rpm to maintain speed on the interstate with 4.10's and 5 speed.

I don't know how fast you drive, but even with 205/75 tires and 4.10 gears 70 MPH would only be turning 2750 RPM. 3350 would be an 85 MPH cruise. Personally, I wouldn't drive any MJ (or XJ) that fast, even if it were legal (which, of course, it isn't).

 

 

yes. you are still taking this too literally....I didn't care to do the math. I just wanted to know what it would run, and STILL I am telling you that I was using a figure of speech.

 

 

I don't CARE about anything else but the fact that I DON'T want to run it on the interstate at 65mph above 2600rpm. so, with my options, I'm doing just fine.

 

 

drop that subject, because it doesn't matter.

[Eagle]

drop that subject, because it doesn't matter.

To you.

 

Someone else reading this thread might want to know what RPM he would actually be running with a specific tire and gear combination.

[JeepcoMJ]

drop that subject, because it doesn't matter.

To you.

 

Someone else reading this thread might want to know what RPM he would actually be running with a specific tire and gear combination.

 

then don't argue with me, because It doesn't matter to me. at all.

[Jeepman]

Someone else reading this thread might want to know what RPM he would actually be running with a specific tire and gear combination.

 

Well this is Why I posted that Gear calculator as personel opion gets in the way all the time not to mention ego, we all drive differently and require different gearing based on how we drive...

 

Just run the gear calculator I posted and you will get in the ballpark as to where you should be based on your needs...

[DJM/78]

I do 75 mph on the way to work every day , sits at about 3000 RPM , maybe out here on western side of things we drive a little faster , I wouldn't drive my truck if it couldn't get

out of its own way . 31"s with the 456's , it straight gets up and hauls , once I upgrade to 33's I'll even get a better highway ratio . So my opinion is just throw the 410/411

gears in it and be done with it . All in all I've improved gas milage as I've learned the new gears and how they effected my gear box .

[kastein]

that said, I was using a figure of speech when I said "redline". what I should have said is that I don't feel like running @#$% ridiculous high rpm's at constant. I like gas mileage...it doesn't need to hit 3,000 rpm at a constant.

If I were a betting man, I would be willing to bet that with two otherwise identical MJs, one that ran 3,000 RPM at 70 MPH would deliver better gas mileage than one with stock gears and a 5-speed, that runs 1960 RPM at 70 MPH. There's just nothing like running UNDER the torque curve to boost your gas mileage ... NOT.

 

3,000 RPM is not "@#$% ridiculous high rpm's" for these engines -- it's the speed they were designed to run at.

I get 18.change mpg with an AW-4 and at least a thousand pounds of junk (4.0, aw4, np231, driveshafts, axleshafts, two toolboxes, a toolbag, an engine hoist, two bins of spare fluids, plus camping gear) in the back doing 80-90mph, averaging about 85. Did that for the full length of I-84 last Friday night. Oh, and that's with a 4.0L engine with over 220 thousand miles on it.

 

Same exact setup, going the other direction and only traveling at an average of 60mph, I got 22.3mpg.

 

I like to keep it around 2500rpm normally... in my case this means 75-80mph ('91 AW-4 overdrive, TC locked, 3.55:1 gears, 225/75r15 tires with decent tread.)

 

As for how it handled at 85mph, heavily loaded? Like a cadillac. I could still panic stop just fine, and did, when a trucker nearly merged into me just past Hartford due to some bonehead on a cellphone nearly merging into him.

 

http://www.grimmjeeper.com/gears.html should help you a lot... fill in the trans/transfer case/gears/tires and it'll do all the hard work for you.