Regearing Questions? READ THIS!

[MoparManiac]

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.

Sorry didn't really go back and read the page before.

I think there are a lot of variables, and tire weight is definitely one of them.

33" BFGs on alum. rims vs. 33" MTRs on steelies is a different scenario.

I'd probably go for 4.56s on 32s, even with the AX-15s gearing (yes I've driven one). That way if you ever have the desire to get 33s, you'll be fine. Who the hell goes faster than 75-80 mph in their XJ?

The fastest I had ever gone was close to 100 mph when I was only on 31s (downhill). I wouldn't even try to do that now, or when I was on 33s.

 

[Char-Broil]

The problem was not that I could not pull 3000 rpm. Hardly, in fact, 72 MPH was around 4200 rpm, not 2648 as the calculator and chart will tell you. I don't know why this is but I had used a GPS. And all technicalities aside, it was always just plain hard to keep up with traffic around here, which typically travels at 70+.

 

[89xj]

Hardly, in fact, 72 MPH was around 4200 rpm,

that cant be right. maybe in fourth gear

 

[muduck18]

Well I don't know about the Tach numbers.
That jeep is sitting a mile from my house, with 32in BFGs on it right now...
if you want to know what its like come on out, and we will take it for a spin, I am sure Jon won't mind....

 

[muduck18]

Sorry didn't really go back and read the page before.

need to be sorry we're all friends here....:wave1:

I think there are a lot of variables, and tire weight is definitely one of them.

33" BFGs on alum. rims vs. 33" MTRs on steelies is a different scenario.

I'd probably go for 4.56s on 32s, even with the AX-15s gearing (yes I've driven one). That way if you ever have the desire to get 33s, you'll be fine. Who the hell goes faster than 75-80 mph in their XJ?

yeah I agree. big differences wheel mass so very good point.

The fastest I have ever gone was when I was checking my Speedo... and some with a GPS, i tracked it to 96MPH that was with 4.56 and 33's
and that was Redline maybe a little past.

 

[saburai]

need to be sorry we're all friends here....:wave1:

yeah I agree. big differences wheel mass so very good point.

The fastest I have ever gone was when I was checking my Speedo... and some with a GPS, i tracked it to 96MPH that was with 4.56 and 33's
and that was Redline maybe a little past.

With the AW4 that's right at 4500, sounds about right:cheers:

 

[saburai]

in fact, 72 MPH was around 4200 rpm, not 2648 as the calculator and chart will tell you. .

More like third with a AX15/33/4.56

Numbers don't lie. Sounds like some thing is/was way off...

 

[muduck18]

More like third with a AX15/33/4.56

Numbers don't lie. Sounds like some thing is/was way off...

Do you mean AX15/32/4.56?

And what is the estimate for the actual circumference of the tire?

Numbers don't lie, but whats on paper doesn't always add up in the real world.

 

[muduck18]

need to be sorry we're all friends here....:wave1:

that was supposed to say "NO need to be sorry..."
:cheers:

 

[saburai]

Do you mean AX15/32/4.56?

And what is the estimate for the actual circumference of the tire?

Numbers don't lie, but whats on paper doesn't always add up in the real world.

Oops!:eyes: my bad!

Calcs say 4826 RPM w/32 in 3rd or 4346 RPM in 3rd w/33...

4250 RPM gives 112 MPH in 5th w/32's that is of course on paper.

"Whats on paper doesn't always add up in the real world."
Very true but it ain't usually that far off...

It's all good Pal! We are all friends here:wave1:

 

[JeepXJFan]

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.

 

[cal]

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.

http://www.grimmjeeper.com/gears.html

30" tires, 70 mph, aw4

4.56 : 2681
4.10 : 2411

 

[JeepXJFan]

You rock cal!

Thank you sir.

 

[Flyfisher]

wow....lots of talk and controversy. Anyway...I'm hoping I picked the right (correct) gears. Have a 4.0 with the AW4 and NP242. Just re-geared to 4.56:1 to run my 33x10.50 tires. I'm thinking it will put it back to a little bit below (lower) than stock gearing. Perfect for highway...good for off-road. Hope I won't be sorry I didn't go 4.88:1!

 

[ILLXJ]

wow....lots of talk and controversy. Anyway...I'm hoping I picked the right (correct) gears. Have a 4.0 with the AW4 and NP242. Just re-geared to 4.56:1 to run my 33x10.50 tires. I'm thinking it will put it back to a little bit below (lower) than stock gearing. Perfect for highway...good for off-road. Hope I won't be sorry I didn't go 4.88:1!

Shoulda went 4.88's. JIM.

 

[HaleYes]

wow....lots of talk and controversy. Anyway...I'm hoping I picked the right (correct) gears. Have a 4.0 with the AW4 and NP242. Just re-geared to 4.56:1 to run my 33x10.50 tires. I'm thinking it will put it back to a little bit below (lower) than stock gearing. Perfect for highway...good for off-road. Hope I won't be sorry I didn't go 4.88:1!

4.88's is where it's at.

 

[DanNJeep]

So then I've got to ask. If the 4.0 likes to run at 2500 - 3000 then why didn't the factory gear it that way? Unless your traveling way past the speed limit (how fast you drive is a personal choice and the factory can't account for that) the stock combinations don't get you anywhere near those rpm's.

Personaly my XJ ran 4.0/AW4/3.55/31's for about 280K and loved it.

 

[89xj]

So then I've got to ask. If the 4.0 likes to run at 2500 - 3000 then why didn't the factory gear it that way? Unless your traveling way past the speed limit (how fast you drive is a personal choice and the factory can't account for that) the stock combinations don't get you anywhere near those rpm's.

Personaly my XJ ran 4.0/AW4/3.55/31's for about 280K and loved it.

my take would be that they are geared from the factory for mileage and emmisions purposes and not for peak performance output.

engines/vehicles peak horsepower and torque is acheived well over there cruising rpm range.

 

[muduck18]

So then I've got to ask. If the 4.0 likes to run at 2500 - 3000 then why didn't the factory gear it that way? Unless your traveling way past the speed limit (how fast you drive is a personal choice and the factory can't account for that) the stock combinations don't get you anywhere near those rpm's.

Personaly my XJ ran 4.0/AW4/3.55/31's for about 280K and loved it.

Most here will say, that the added mass of the tires will create more strain on the engine..

But my jeep 4.0/ax-15/4.56/33's is perfect.

The bottom line for me is this.
That power band is what you need for getting up and going.
The sweet spot for keeping the jeep at speed is not the same as its peak output.
Lets face it, if you run something at peak output all the time you don't have any option to get just a little more out of it. (as discussed earlier.. passing gear?)

however, the AW4 does need lower gearing than the AX-15

 

[DanNJeep]

my take would be that they are geared from the factory for mileage and emmisions purposes and not for peak performance output.

engines/vehicles peak horsepower and torque is acheived well over there cruising rpm range.

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