Regearing Questions? READ THIS!

[Ivan]

I run 33's and 4.56 on an ax-15...
I run out of tach room before I run out of power.
if you never plan to go bigger than 32's don't do the 4.56 IMHO On the 5sp you will run out of gears way to fast.
PM muddgygp
he currently has 4.56 and 32's and i think he will tell you don't do the 4.56 and 32's
IMHO

I run 4.56's and a 5 spd with my 32's and rather like it. I care more about low end umph, more so than top end speed; which if you have a Jeep that is what you need. I don't drive above 70mph, so top end speed really is a non issue for me. Cal's speed chart is dead on with what I experience. I have no regrets or complaints....

 

[DougJ]

This is a great thread, and it's a huge help to allot of guys like me. Getting the wrong gears would be a huge mistake!
I'm looking at re-gearing when I get home from Iraq. The Jeep is sitting on a BDS 4.5" lift and 245/75 16 MTR's. (31's - 2006 Rubicon Wheels/tires) I'm planning on going to 32's when these wear out. I live in Prather, CA in the foothills of the Sierra Nevada so I drive up and down hill every day. This thread is making me reconsider my initial assessment that 4.10's would be the way to go, and I'm starting to think 4.56's would be better, even if I have to replace the tires early. I'm hoping to find a decent HP Dana 30 for my '01 and regear that, along with doing a few other things.

So thanks to everyone for all the great info!:cheers:

Doug

 

[Phil]

I had 4.88's and 31's for a while. With that combo I drove to Rubicon (600miles? or 400? or something like that) wheeled there and drove back. It drove perfect. My top speed was about 68mph at 3000rpm. I got great good fuel economy (16~17mpg) too. I had 235's with 4.11's and that was also a match made in heaven. Btw, I used to daily drive that rig 120 miles a day.

That must not have been the time you broke your axle...HOUSING.

 

[muduck18]

With an ax15, 4.56, and 32's, you should have....

......

... how fast are you trying to go? The 4.0 wants to sit above 2500 on the highway, between 2500 and 3300.

What the 4.0 does NOT want, is to work harder. It would rather sit at 3300 RPM's for six hours than be bogged down trying to push big meats. Its an i6, not a v8.

Thanks Cal, what you posted there, is really not too far off from what I get with 33's (which measure shorter than actually 33...)

You are absolutely right about the engine. On the hwy I set in a sweet spot at about 70mph.

Off road the crawlier the better, but for a DD though, its a tough call....... I don't think I would do 4.56, and 32's.. but that's me.

 

[Kejtar]

That must not have been the time you broke your axle...HOUSING.

That is correct. And the axle housing broke cause it came from a vehicle I rolled (started on wheels and ended up back on wheels) which as it looks damaged it.

 

[saburai]

Thanks Cal, what you posted there, is really not too far off from what I get with 33's (which measure shorter than actually 33...)

You are absolutely right about the engine. On the hwy I set in a sweet spot at about 70mph.

Off road the crawlier the better, but for a DD though, its a tough call....... I don't think I would do 4.56, and 32's.. but that's me.

Why is that? It works out to a net difference of 80 RPM...

Road RPMs at Given Speed with 4.56:
32's = 2648 RPM @ 70MPH
33's = 2568 RPM @ 70MPH

 

[muduck18]

Why is that? It works out to a net difference of 80 RPM...

Road RPMs at Given Speed with 4.56:
32's = 2648 RPM @ 70MPH
33's = 2568 RPM @ 70MPH

I have 4.56-33s and a 5speed
I like it,
But I wouldn't run any smaller tire on a daily driver.
I think the reason is obvious. 2568rpm is high... 2648rpm is higher.
For off-road that is fine.
For daily driving I really wind through the gears fast, and its hard to know when to use 1st, if ever.


Now if you ever think you might possibly go bigger than 32's no question.
If you ever plan to run a trailer no question.

But why am I still talking about this, I already geared my Jeep and I love it?

 

[Kejtar]

Why is is so hard for you guys to understand?

I have 4.56-33s and a 5speed
I like it,
But I wouldn't run any smaller tire on a daily driver.
I think the reason is obvious. 2568rpm is high... 2648rpm is higher.
For offroad that is fine. For DAILY DRIVING I WOULDN'T DO IT.

Now if you ever think you might possibly go bigger than 32's no question.

But why am I still talking about this, I already geared my Jeep and I love it?

OK.... why wouldn't you run it? IIRC peak output is closer to 3K rpm's on the 4.0

 

[89xj]

with 32's and a 5speed, it comes down to whether you rather be geared a little low(4.56) or a little tall(4.10) and if 32's are the biggest you will ever go. personally, i would rather be a little low.

my 89 speed, 4.10 gears with 31's(which are around 30.4") the rpms are at 2500 when going 65mph in 5th gear.

 

[cal]

I have 4.56-33s and a 5speed
I like it,
But I wouldn't run any smaller tire on a daily driver.
I think the reason is obvious. 2568rpm is high... 2648rpm is higher.
For off-road that is fine.
For daily driving I really wind through the gears fast, and its hard to know when to use 1st, if ever.


Now if you ever think you might possibly go bigger than 32's no question.
If you ever plan to run a trailer no question.

But why am I still talking about this, I already geared my Jeep and I love it?

WHat I don't think you understand is that you would be hurting your jeep if you were to run with less gearing. The engine -WANTS- to be at 2700+ RPM's, its not like you're abusing it.. that is where it runs best.

 

[CanMan]

I have 4.56-33s and a 5speed
I like it,
But I wouldn't run any smaller tire on a daily driver.
I think the reason is obvious. 2568rpm is high... 2648rpm is higher.
For off-road that is fine.
For daily driving I really wind through the gears fast, and its hard to know when to use 1st, if ever.


Now if you ever think you might possibly go bigger than 32's no question.
If you ever plan to run a trailer no question.

But why am I still talking about this, I already geared my Jeep and I love it?

If you live anywhere where there is a hill, you'll want the low gearing.

 

[muduck18]

WHat I don't think you understand is that you would be hurting your jeep if you were to run with less gearing. The engine -WANTS- to be at 2700+ RPM's, its not like you're abusing it.. that is where it runs best.

:worship:
What ever man.

If you live anywhere where there is a hill, you'll want the low gearing.

Agreed.

 

[muduck18]

OK.... why wouldn't you run it? IIRC peak output is closer to 3K rpm's on the 4.0

Just because Peak is 3k doesn't mean that I want to be running at peak output all the time.

 

[Kejtar]

Just because Peak is 3k doesn't mean that I want to be running at peak output all the time.

So you don't want to run it where the engine is the most efficient? The 4.0 as Cal said is tuned for higher RPM's.

I have currently 2 XJ's that have about 200K each and for most of their life their crusing speed was set at about 3K. My dad's XJ is running an engine out of my rolled one and same thing: it's setup to run at about 3K on the freeway (oh yeah, that one also has about 200K) . All run nice and smooth

 

[89xj]

So you don't want to run it where the engine is the most efficient? The 4.0 as Cal said is tuned for higher RPM's.

I have currently 2 XJ's that have about 200K each and for most of their life their crusing speed was set at about 3K. My dad's XJ is running an engine out of my rolled one and same thing: it's setup to run at about 3K on the freeway (oh yeah, that one also has about 200K) . All run nice and smooth

it depends on what cam the 4.0 has on where the peak or optimum rpm is. i dont think you can put a single number on what the peak rpm is, i think its more of a "sweet spot" and its more of a range.

3000rpms seems a little high for the "sweet spot" i would say its around 2400-2800 rpms when cruising.

i have 4.10 and 31's on my 89 and for me to run 3000rpms on the highway, id be doing over 80mph, thats not something i want to do. i cruise anywhere from 65 to 75mph with a max of about 2800rpms.

 

[MoparManiac]

Just because Peak is 3k doesn't mean that I want to be running at peak output all the time.

That's what I thought until I put on my 35s.

I don't like to be at anything lower than 2500 rpms while cruising.

 

[muduck18]

So you don't want to run it where the engine is the most efficient? The 4.0 as Cal said is tuned for higher RPM's.

I have currently 2 XJ's that have about 200K each and for most of their life their crusing speed was set at about 3K. My dad's XJ is running an engine out of my rolled one and same thing: it's setup to run at about 3K on the freeway (oh yeah, that one also has about 200K) . All run nice and smooth

I Don't think the question was how nice and smooth they run if you drive them at 3k rpm for the life of them.

I am concerned about hi way (65-75MPH) fuel economy as well as the *best* possible off and on road performance

with

32 or a slightly smaller(than 32) metric equivalent.

And with that information.
Given its a 5 speed.
Knowing what I know.
4.10
That is my recommendation for that scenario...
or
I would say skip the 32's
buy 33's
and gear to 4.56

Why must you guys keep attacking my opinion like I am some how causing the 4.0 to die and China's oppression of Tibet?

Also..
The aw-4 and the ax-15 behave very different
When using an AX and running high speeds and High RPMs just the slightest bump in the road makes the engine bounce. (thats why they make hand throttles for off road)
and lifting causes everything to slow down alot more than an aw because when you lift it releases the torque converter and lets it coast.

 

[muduck18]

That's what I thought until I put on my 35s.

I don't like to be at anything lower than 2500 rpms while cruising.

you run 35's and an auto.. I don't see how that applies to 32's and a manual Daily driver with concern about highway economy.

 

[Char-Broil]

Sorry, I have to put in my $.02. I ran 32 BFG AT's and 4.56's on my XJ/AX and it was decent, but I always wanted more tire. I am not kidding when I say MAX speed was about 72, flogging it. I would get stuck in trucks drafts because I did not have the leg to break thru it. I got 33's and from the first drive I knew it was perfect. I wheeled it and LOVEd it. It acutally had a lot more control offroad because of the size and softness of the tires (when aired down). Max speed on the 33's is about 80 or more, but really only comfortable when absolutely necessary, as I'm sure any lifted XJ driver can attest. Honestly for my DD XJ I was in love with 3.55's and 31s with the AX. Would easily get 20-21 MPG. Best I could pull outta the 32's or 33s with the 4.56 was 19, even with an electric fan insdead of the mech one.

 

[saburai]

Re: That's odd...

Sorry, I have to put in my $.02. I ran 32 BFG AT's and 4.56's on my XJ/AX and it was decent, but I always wanted more tire. I am not kidding when I say MAX speed was about 72, flogging it. I would get stuck in trucks drafts because I did not have the leg to break thru it. I got 33's and from the first drive I knew it was perfect. I wheeled it and LOVEd it. It acutally had a lot more control offroad because of the size and softness of the tires (when aired down). Max speed on the 33's is about 80 or more, but really only comfortable when absolutely necessary, as I'm sure any lifted XJ driver can attest. Honestly for my DD XJ I was in love with 3.55's and 31s with the AX. Would easily get 20-21 MPG. Best I could pull outta the 32's or 33s with the 4.56 was 19, even with an electric fan insdead of the mech one.

So let me get this right.

I'm assuming that you are talking about the same AX15/231 Jeep XJ with the above tire/gear combination's.

You stated that there was a large difference in the drive ability of the two.
At 70MPH there is a difference of 120 RPM between the two...

You stated that with the 32/4.56 set up your max speed was 72 MPH and with the 33/4.56 you could pull 80MPH.
At 70MPH with 32/4.56 is 2648 RPM and the 33/4.56 combo at 80MPH is 2934.
I find that difficult to accept.

In fact, unless there is some thing wrong with the truck I can't understand why it is unable to pull 3000 RPM on the hi way.

Please elaborate.