Regearing Questions? READ THIS!

[muduck18]

Yes but isn't mileage a great way of measuring performance?

Efficiency not performance.

And
Efficiency is not equal to performance.

 

[techno1154]

Can anyone calc rpms @ 70mph with 4.10 and 4.56? 30in tires, AW4 1997XJ. Someone had posted charts but they are no longer available.

Just bought a boat to tow and would like to cruise at 70, right now 65 is all she can muster without hunting.

This is what I got using a GPS;...

RPM’s at 55 MPH with 4.10:1 gears running 30” tires 1980
RPM’s at 60 MPH with 4.10:1 gears running 30” tires 2175
RPM’s at 65 MPH with 4.10:1 gears running 30” tires 2360
RPM’s at 70 MPH with 4.10:1 gears running 30” tires 2550
RPM’s at 75 MPH with 4.10:1 gears running 30” tires 2700
RPM’s at 80 MPH with 4.10:1 gears running 30” tires 2920

 

[HaleYes]

Yes but isn't mileage a great way of measuring performance?

When I drove my XJ to Winterfest I averaged 16mpg. 4.0/AW4/4.88's/33's That's nearly all Interstate driving @ 65-70pmh. I don't have a tach so I can't tell you what RPM's I run at highway speed.

What gets me is guys that think the 33's and 4.56's is the best thing since sliced bread. BUT, they've never drove a rig with the 4.88's to compare to. Before I regeared, I was running 33's and 4.10's and absolutly hated it. It was a huge dog in my opinoin. HUGE dog. I drive a 4.56's/33" rig as well as a 4.88's/33" set up before I made my decision.

Bottom line is that preference is really what matters. Some play with number and make big fancy charts with final drive ratios and some other numbers that I'm not sure what they mean. Real world experience and charts on paper don't always agree and, in my opinion....this is one of those times. You may love the 4.56's and that's fine. However, if you don't have anything else to compare them to..........:dunno:

If you're going to regear, do your homework. Drive a rig that has what you're considering. I realize that sometimes it's not doable for everyone, but it's the best way to know if you're going to like it or not.

 

[muduck18]

When I drove my XJ to Winterfest I averaged 16mpg. 4.0/AW4/4.88's/33's That's nearly all Interstate driving @ 65-70pmh. I don't have a tach so I can't tell you what RPM's I run at highway speed.

What gets me is guys that think the 33's and 4.56's is the best thing since sliced bread. BUT, they've never drove a rig with the 4.88's to compare to. Before I regeared, I was running 33's and 4.10's and absolutly hated it. It was a huge dog in my opinoin. HUGE dog. I drive a 4.56's/33" rig as well as a 4.88's/33" set up before I made my decision.

Auto VS Manual is a huge difference!
A manual has no torque converter to lock or slip and it doesn't have overdrive.
Gear ratios for the AX15 is 0.79, for fifth,
AW-4 in OD is 0.753..

Bottom line is that preference is really what matters. Some play with number and make big fancy charts with final drive ratios and some other numbers that I'm not sure what they mean. Real world experience and charts on paper don't always agree and, in my opinion....this is one of those times. You may love the 4.56's and that's fine. However, if you don't have anything else to compare them to..........:dunno:

Agreed, I compared several tire/gear ratios In actual XJ's before i went with 4.56

If you're going to regear, do your homework. Drive a rig that has what you're considering. I realize that sometimes it's not doable for everyone, but it's the best way to know if you're going to like it or not.

Agreed!

 

[DanNJeep]

"Efficiency not performance.

And
Efficiency is not equal to performance. "

I would tend to disagree somewhat. Efficency is a measure of performance if you define performance as the way a vehicle performs in all aspects. Otherwise if you're simply defining performance as in speed or towing what in the hell are we doing driving Jeeps anyways?

I would agree efficency is not the only measure of performance but it certainly is an aspect of it. I guess it all goes back to how one chooses to build their Jeep.

 

[cal]

"Efficiency not performance.

And
Efficiency is not equal to performance. "

I would tend to disagree somewhat. Efficency is a measure of performance if you define performance as the way a vehicle performs in all aspects. Otherwise if you're simply defining performance as in speed or towing what in the hell are we doing driving Jeeps anyways?

I would agree efficency is not the only measure of performance but it certainly is an aspect of it. I guess it all goes back to how one chooses to build their Jeep.

.... what? You don't realize it, but you're speaking nonsense.


The 4.0 is more efficiant, and has better performance, at higher RPM's.

The factory geared the way they did for comfort and emissions. end of story.

 

[muduck18]

"Efficiency not performance.

And
Efficiency is not equal to performance. "

I would tend to disagree somewhat. Efficency is a measure of performance if you define performance as the way a vehicle performs in all aspects. Otherwise if you're simply defining performance as in speed or towing what in the hell are we doing driving Jeeps anyways?

I would agree efficency is not the only measure of performance but it certainly is an aspect of it. I guess it all goes back to how one chooses to build their Jeep.

Well I am talking about the motor.

When its producing the most HP (performance measurement) its consuming more fuel than when its running more efficient (ratio of performance to fuel consumption)

Peak performance output of the motor is not where I want it operating at all times. Even if the Jeep can be configured to make peak operating performance the same as peak efficiency (based on a MPG) then you don't have any room for acceleration.

 

[muduck18]

.... what? You don't realize it, but you're speaking nonsense.


The 4.0 is more efficiant, and has better performance, at higher RPM's.

The factory geared the way they did for comfort and emissions. end of story.

I think you are speaking nonsense.

 

[cal]

I think you are speaking nonsense.

with 4.88's and 35's, my XJ will pull 19-20 on the highway.

With 5.13's and 35's, Jes pulls 22-25 on the highway.


Go see what someone gets with say, 4.10's and 33's.


Afterwards, go look at the cam profile of both early and late 4.0's..

the engines want to run at 3,000 RPM's all day long.

 

[muduck18]

with 4.88's and 35's, my XJ will pull 19-20 on the highway.

With 5.13's and 35's, Jes pulls 22-25 on the highway.

proof or BS


MPG of my Jeep since I have owned it. logged every one of the 252 Times I have filled with gas.
Each drop in fuel effieciency. is a regear to a lower gear ratio. (tank 35ish and tank 222ish.)

 

[cal]

Call all the BS you'd like, it won't make it BS. Search a while and you'll find most people here agree with me though.

I calculate each tank and fillup, I don't record them.

Can't pull a future tank for you as the rig was rolled over New Years weekend. I'm working on building a new one now, and it will never have a 4.0 to measure from..

 

[DanNJeep]

The BS meter is now officially pegged. I'll go 18, I'll even go maybe 20 (not really). But there is no way a not so smooth XJ lifted with 35's and running 5.13's is getting 25 mpg! Come on dude!

I've had multiple Jeeps of various styles, WJ's, ZJ's, XJ'S and a TJ. Some stock some modified. None of them approached 25 except the stock WJ.

The more energy it takes the higher the fuel consumtion. Big tires equals more rolling resistence, higher in the air to fit those tires equals more wind resistence, higher RPM to push all that thru the air requires more energy to turn those RPM's. All of this adds up to less mpg.

So what your contention is a lifted, big tired, geared XJ is getting better economy than my stock WJ. Which has much smaller tires, lower to the ground and is slicker going thru the air.

 

[saburai]

The BS meter is now officially pegged. I'll go 18, I'll even go maybe 20 (not really). But there is no way a not so smooth XJ lifted with 35's and running 5.13's is getting 25 mpg! Come on dude!

I've had multiple Jeeps of various styles, WJ's, ZJ's, XJ'S and a TJ. Some stock some modified. None of them approached 25 except the stock WJ.

The more energy it takes the higher the fuel consumtion. Big tires equals more rolling resistence, higher in the air to fit those tires equals more wind resistence, higher RPM to push all that thru the air requires more energy to turn those RPM's. All of this adds up to less mpg.

So what your contention is a lifted, big tired, geared XJ is getting better economy than my stock WJ. Which has much smaller tires, lower to the ground and is slicker going thru the air.

I gotta agree 100% with that. 25mpg! Come on...

 

[muduck18]

I gotta agree 100% with that. 25mpg! Come on...

Well if you look at my chart, I did reach that one time.
right around fuel tank number 27.. it looks like i got just over 25Mpg but at that point it was stock,
and my Fiancee was living 400Mi away from me, so that tank was probably 100% Highway and 100% non stop.

 

[DanNJeep]

OK just to satify my own curiosity I went to the EPA's website and looked at what owners of assumably stock XJ's were reporting across the country. Keep in mind these are generally stock, meaning lower, lighter, smaller tired, and generally just easier to push thru the air. No one consistently reported much of anything near 25 mpg. Here is the link -

http://www.fueleconomy.gov/mpg/MPG.do?action=browseList2&make=Jeep&model=Cherokee 4WD

I just don't see how it's possible for a 35" tired, lifted, geared, heavier and overal harder to push thru the air XJ can get BETTER than these stockers.

 

[markaboo929]

Idling ALL the way down a 300 mile mountain!!!:doh: LOL

 

[89xj]

The BS meter is now officially pegged. I'll go 18, I'll even go maybe 20 (not really). But there is no way a not so smooth XJ lifted with 35's and running 5.13's is getting 25 mpg! Come on dude!

I've had multiple Jeeps of various styles, WJ's, ZJ's, XJ'S and a TJ. Some stock some modified. None of them approached 25 except the stock WJ.

The more energy it takes the higher the fuel consumtion. Big tires equals more rolling resistence, higher in the air to fit those tires equals more wind resistence, higher RPM to push all that thru the air requires more energy to turn those RPM's. All of this adds up to less mpg.

So what your contention is a lifted, big tired, geared XJ is getting better economy than my stock WJ. Which has much smaller tires, lower to the ground and is slicker going thru the air.

the best ive got on my 89 with 31's, 5spd, and 4.10 gearing was around 22mpg. in the summer when its really hot out, my 89 gets really good mileage on the highway turning anywhere between 2500 -2900rpms. the bad part is, around town driving with lots of stop signs i only get about 15 mpg.

 

[saburai]

Idling ALL the way down a 300 mile mountain!!!:doh: LOL

That would believe...

 

[Glyphic]

if you read that mpg chart you just linked you will notice it bases that number or percentage of highway travel and stop and go traffic. Some of those numbers for stock jeeps did reach the 25 MPG mark, so I'm sure with proper gearing and non-stop travel it is very much possible.

 

[saburai]

It may, with the perfect conditions, be possible.
However, I strongly doubt that a lifted XJ with 33-35" tires and the associated accessory's would be able to pull 25mpg with any regularity...