4.0 Lo

yeah after i put 31s on my xj 4.0 ho it seens liker it ALOT weaker than it used to be. like if im going up any hill at all i need to downshift. im talking about the slightest inclines. i know i have a bad cat could that be causing me this weakness? its got a new dist cap and rotor, and a cai. any suggestions appreciated.

probably because you touch yourself at night...


its the bigger tires stealing your power, only 2 real ways to fix it
1.take them off
2. regear

Did you regear your axles to go along with the bigger tires?

5spd trans ? went from say...235's to 31's?

yeah i figured the 31s would decrease power i just didnt think theyd make this big of a difference.

and no i ddint regear, i was gonna mention asking if i should but id get flamed and told to get aome 35s and a d44 and a kajillion other things.

heres the skinny....

with a 5 spd you have 3.07 gears. IF you go to 3.54 with 31's...(which is what I'm stuck with at this time) it would ALMOST be like it was before with your 235's.

5th gear is now UNUSEABLE. and with my 3.54 gears...damn near UNUSEABLE.

I'm considering 4.56's, although I have a complete 4.10 front axle.

BUT I also have 3 kids and next to no MONEY. So...if you got the money...regear.

I think I'm just gonna stick with 4.10's. But don't know at this point.

Good luck.

DECISIONS, DECISIONS....


BTW...if you present yourself as just asking good solid questions...you shouldn't get flamed. It's guys who act like idiots that get targeted.

There is a sticky around here with gearing and all the other goodies you should consider at this point. I believe its at the top of this Forum.

you said with a 5spd i have 3.07, are the 3.54 out of an auto? or what is the gearing in an auto? and are they swappable easily?

edit: found that post that says the autos have 3.55s. also could i put the front 4.10 out of my 86 2.5 into my 93s front. they are both d30s.sorry if this is another dumb question.

with 3.07s u wanna gear lower, numerically higher. 3.54 or 3.73 found in autos wont really improve your acceleration and power. if u plan on stayin with 31s go with 4.10s. you will also get a lot better gas mileage.

Nick

jayuu said:

you said with a 5spd i have 3.07, are the 3.54 out of an auto? or what is the gearing in an auto? and are they swappable easily?

edit: found that post that says the autos have 3.55s. also could i put the front 4.10 out of my 86 2.5 into my 93s front. they are both d30s.sorry if this is another dumb question.

Click to expand...

I had to swap complete axles. I work for a wrecking yard so availability was NOT an issue.

IF your front ends are the same....NON DISCO / or DISCO yeah you can do it.

It would make it much better. Should one front be disco and the other non...don't know HOW that would work right off hand.

But yeah....auto, 4.0's are 3.54/3.55 gears.

carp , yeah the 86 is that vacuum disco crud, and the 93 is the non vacuum. but if i could switch it itd save me the 200 for the front r&p. is rustys a good place to get a rear chry8.25 4.10 rp set. my 89s got the weak d35 so i cant swap the rp and i dont want to change the axles. plus i like to still use it as a beater.

rustys??? naw....

Try Raw Brown...Naxja member, or maybe Randys Ring and Pinion.

The vacuum disconnect was probably a "fuel economy" thing, and done for federal CAFE standards. It was done away with a little later, retaining the NP231 (and the NP242 never had it.) As long as everything's in good shape, ditching the disco should be no trouble - I just "forced" it over of my 87 and forgot about it - and quite a few others have as well. You should have no trouble if you go to a "non-disco" axle up front.

If you can get an automatic donor vehicle, you should be able to score a pair of axles geared 3.54/3.55 - and that works fairly well with 30's and 31's. I'd say 4.10's would be a better choice for a road/rock rig, but they're a little harder to locate, and I think both carriers "break" at about 3.73 - meaning you'd have to get a carrier of some sort as well as gears (and doubling or tripling the cost of the regear.) At that point, it would probably be worthwhile, since you're doing the entire differential, to think about adding your LSD/Lockers while you've got it torn entirely to bits. Detriot, Eaton, and ARB all make lockers that replace the carriers - and there are probably more that I'm not thinking of.

If you ask intelligent questions, you (probably :laugh3: ) won't get blasted. However, we get our share of questioners that seem to hail from Moron Mountain, and it gets a little wearing.

One of the best things you can do for yourself - here or anywhere else - is to remember that we will probably never see you - except by what you write. Which means you are going to be judged not only by what you say, but in how you say it. What does that mean? Take the time to think about what you say before you type it. Make it look nice - that makes it easier to read. Polish your grammar and spelling, if you think you need help. Follow to standard rules of writing formats - they've been around as long as they have for a good reason.

Remember that readability is key to interaction in any written forum - like this - and you can enhance your known reputation simply by treating spelling, grammar, punctuation, and formatting as serious. I'm not trying to say that you're doing anything wrong, but it seems to me like you might be fairly new at this sort of thing (written format interation - not an opinion of your mechanical skills) and I'd like to give you a few pointers.

It's also worth remembering that an occasional "typo" won't be a problem - we all do that every now and then. But, the more polished your writing becomes, the more likely you are to get good, useful answers to your questions, and the better you'll feel about the way people write back.

I've been thinking about this for a while, and I'm trying to work out some sort of "netiquette" thing as it applies to the written word. None of us are at all perfect - but it shows if you think about what you say before you say it, and it gets you much better responses. You'll see that anywhere you go!

5-90

Mine is a 4.0/AW4/3.55's and I'm rollin on 235's but plan on goin to 31's later. The only time I have to use low gear (1st or 2nd) is goin downhill to keep from burning up the brakes and uphill.

:compwork: Ok, assuming you have a 4.0, AW-4 with chrysler 8.25 and 3.55's, going from stock tire size, 225/75R15's to 31's, you'll loose 8.8% change from stock, so think of that as 8.8% in gearing. Also, at 65mph, you'll be loosing roughly 180 RPM. Something to think about.

ok i have a 93 4.0 ho 5spd ax15 and np231j with the dana 30 non disco(i beleive, there isnt the vacuum stuff) front, and a chrysler 8.25 rear. it is my main rig.

i also have a 86 2.5 5speed with a dana 30 disco front(all the vacuum stuff) and a dana 35 rear. it is a semi donor vehicle. the 4 wheel doesnt work so i can trade the front axle if needed. but id like to keep it running as a beater.


i read that usually the 2.5s have 4.10 gear ratio. so can i switch the 86s axle into mine? oir then id need to switch over vacuum stuff. but could i jsut switch over the carrier and the 4.10 into the front of the 93s housing and such? then id get a 4.10 kit for the rear and be all good.

i know i ned to regear, but im just wondering if its possible to switch so i wouldnt need to spend the extra $200 for the front. or if its worth the time and effort to switch it all over or just buy the fronts too.

all this is making me think of getting the axle out of an explorer because i think vie read those are also 4.10 stock and a stronger axle.

thanks again for all the help.

The 4 cyl XJs often have 3.73 as well. I have that ratio in my '87 Comanche with 4.0L and 5 speed with 33" tires and it rocks. With 210,000 on the clock, I can still get the tires rotating from a stand still. Mind you, I have HO injectors in it with a slightly shaved head.
3.55 is a dime a dozen, and I almost went with that ratio. Mine was originally 3.07 and while it cruised at high speeds (worked nice for going to and from Poulsbo daily) and got decent economy (18 mpg, now 20 mpg) it lacked power (I could only use 5th gear over 50 mph and on flat terrain, now I cruise up a 7% grade in 3rd from a standstill and nearly have time to shift before the top!)

ill check out the 86s gearing today

Before you mess with the front axle, confirm that the axle in your '86 is a 4.10 ratio. It probably is, but it could be a 3.73.

Exchanging the gears between the two front axles would keep your '93 with the non-disco front axle, but it requires setting up two pairs of gears. It's generally not possible to get used gears set up exactly the way they were in the original axle, so they may be noisy. Certainly not an issue in a beater, but maybe an issue in a daily driver.

But however you get there, I agree that going with 4.10s is the right choice. 31s through 3.73 gears is exactly the same overall final drive ratio is stock tires with 3.54s. I ran my MJ with 31s and 3.73s. It's very driveable on the street but I would have liked more gear on trails. The 3.73/31 combination was an accident. I bought the gears to run in my XJ with 30" tires, then I acquired the MJ and, like you, quickly found that 31" tires with 3.07 gears was a less than optimal setup. I had not installed the gears in the XJ, so I put them in the MJ.

Have you considered just buying a junkyard front axle from a 4-banger to get the 4.10s? If you swap the gears around between the ones you've got, you should replace seals and bearings, and that will probably cost you about as much as a junkyard axle.

yeah thats crossed my mind. also crossing my mind is a junkyard explorer axle. that way id have a slightly stronger rear. if i got 4.10s new for the rear would i also need a new carrier? and are there any 2.5s with a chrysler 8.25 rear with 4.10s?

Swapping gears in your current axles is NOT to be taken lightly because it is NOT a simply "bolt-in" procedure. It requires a couple special tools and a hell of a lot of patience with some skill and luck mixed in. If the gears aren't set up *perfect*, you can destroy them (and ruin other parts too) within a few miles. There are only a few things that I feel it is worth paying a professional to do, and the others are rebuilding an automatic tranny and the machine work to an engine. It can cost $200 or more in labor PER AXLE for gearing (not including the cost of parts) which is why many of us seek out axles that already have the gears we want (or as close to ideal as we can).
Jeep on!
--Pete