4.56 on 31's

[GSequoia]

For some reason, once you start hitting above 4000 repeatedly, they let go. The only 4.0s and 2.5s I have seen pop ( in person ) was when someone held them at the red line a bit too long.

Unless you're running like 23'' car tires, I don't think it's possible gear it low enough to be at a sustained 4000RPM on the highway haha.

Maybe if your engine is crap.

Comfy cruise for me is 2800 - 3200. Hill climbing is 4000 - 4500, sometimes for an extended period of time while pulling large grades while heavily loaded.


Wheeling will see bursts up to redline (Renix Jeep, rev limiter is called valve float).


My 4.0 hasn't exploded yet.

 

[sgtmack]

I ran 31's and 4.56 gears for several years before I went to 33's. Traveled all over the country with it. Right after I re geared my sig line was 31's and 4.56 gears should have been how it came stock.
It appears that most who recommend 4.10's are the ones who didn't try deeper gears. Most of the 4.56 guys would not want to go with less gearing.
Will 4.10's work, of course. But 4.56 gears work better.

 

[Miller88]

I ran 31's and 4.56 gears for several years before I went to 33's. Traveled all over the country with it. Right after I re geared my sig line was 31's and 4.56 gears should have been how it came stock.
It appears that most who recommend 4.10's are the ones who didn't try deeper gears. Most of the 4.56 guys would not want to go with less gearing.
Will 4.10's work, of course. But 4.56 gears work better.

A lot of people are trained to think lower RPM always = better gas mileage, or they think that the 4.0 is only good under 2000RPM.

Right now with 31s and 3.55s I get nearly 20MPG out of it on the highway not using OD. With 4.56, I could use OD and I would be turning practically the same RPM. However, it would use less power to get rolling (so better MPG) and hills would be easier on it.

The only reason for the taller gears (ie 3.07 on 4.0 / 5 speeds) is for the EPA test cycle. A vehicle, unloaded, sure - it's going to get better mileage practically idling down the road. If you load it up with people , gear, recovery bumpers, lift, tires, etc ...

 

[Hillbilly XJ]

I followed the guide of 4.56's for the 33"'s and really wish that I had went with a set of 4.88's or even 5.13's if I move to a 35" tire later.

My mileage improved considerably when I went from the stock 3.55's to the 4.56's with the 33's almost 4-5 mpg in fact and not all the up/down shifting on the highway on level ground, lots of drag and heavy.

 

[87manche]

Wheeling will see bursts up to redline (Renix Jeep, rev limiter is called valve float).


My 4.0 hasn't exploded yet.

I lol'd.

allegedly I've run a 4.0 @ 6000+.

allegedly

 

[sunburned]

I followed the guide of 4.56's for the 33"'s and really wish that I had went with a set of 4.88's or even 5.13's if I move to a 35" tire later.

My mileage improved considerably when I went from the stock 3.55's to the 4.56's with the 33's almost 4-5 mpg in fact and not all the up/down shifting on the highway on level ground, lots of drag and heavy.

Yup, I had 4.56's and 35s for a while and wish I had more gear. Anytime I was below 50, I'd put the shifter in 3 so it wouldn't bog the engine and drone like hell.

 

[kippo1]

I geared 4.56 for 33's and I ended up with some 33x12.5 tires. I hated how much they stuck out and traded this past weekend for some practically new 31x10.5. So now im on 31's with 4.56 and like it better than the 33's on 4.56.

if I ever go to 33's again I will gear 4.88

 

[Tony_SS]

I decided on 4.10's for a few reasons.. the calculations I came up with was that 4.10's on 32's (31.3) were very close to the ratio's on a 100% stock jeep. So that's what I was shooting for. Mine is basically an OEM jeep with lift and tires.. no heavy gear, bumpers, racks, winch etc. If I was running all that extra weight I would have went 4.56. We have more long stretches that I cruise at 70mph so I'd rather keep the RPM lower than higher. It all comes down to personal preference, the setup and how it's used. For the OP, it sounds like 4.10's on his 31's are the ticket, but take my .02 for nothing because I have not run that setup.

 

[Tony_SS]

Something else to consider when using online calculators or doing your math, is the actual tire size under a load.. I measured my "31's" this morning and the actual, real world height is 29.75".

Go according to mr. grimm jeeper,

4.0 AW4 with 4.10's and 31's (29.75") I will be spinning 2385 at 65mph
If I go to 32's (30.75") I will be at 2307 at 65mph

Which for me is ideal, as I can run a lift and bigger tires and till be as close to factory ratios as I can be.

 

[markw]

Under load also means pulling weight. 4.56's will work better when you're loaded with camping gear or pulling an M416 and hit any reasonable hill.

 

[Levathain]

So I ordered the 4.10 and had them installed, I now regret not going to 4.56. I'm at around 2300rpms at 65 and 2500rpms at 70. The power on highway blows going 60 and the city is mediocre. Whoever is going to regear when you get 31 go 4.56, screw everyone that says 4.10 end of story.

 

[cal]

Indeed. I have never thought "I wish my gears werent so deep".

 

[notamos]

So I ordered the 4.10 and had them installed, I now regret not going to 4.56. I'm at around 2300rpms at 65 and 2500rpms at 70. The power on highway blows going 60 and the city is mediocre. Whoever is going to regear when you get 31 go 4.56, screw everyone that says 4.10 end of story.

I've told a million people this & nobody ever wants to listen. I have a fairly light XJ running 31" BFG ATs - and 4.56s. In my previous XJs, I've had:

88 XJ w/ a manual, 3.55 and 33s -> ok, but nothing to right home about
99 XJ w/ an auto, 4.10 and 31s (not much armor/extra weight) -> again, ok
99 XJ w/ an auto, 4.56 and 31s -> perfect IMHO

 

[Levathain]

After spending 1300 bucks to regret now going deeper is no fun, please everyone regear deeper, if the chart says one thing for stock always go 1 gear deeper. Don't make the same mistake I just made, it's painful.

 

[Levathain]

I went with 4.10 because I knew I was only going to run 31's n it seemed like everyone who should get 4.56 was if they were going to move to 33's. well I'd rather run 30's or something now, like to turn back time n buy the 4.56

 

[the_weirdo]

After spending 1300 bucks to regret now going deeper is no fun, please everyone regear deeper, if the chart says one thing for stock always go 1 gear deeper. Don't make the same mistake I just made, it's painful.

 

[Tony_SS]

Well that sucks. Thanks for following up. It makes you wonder why 'half' the people are 'ok' with it though.

At least I'm only getting the rear done today. If the 4.10's don't cut it, I supposed I'll sell off an organ and regear the rear again before I do the front to match.

 

[Tony_SS]

Indeed. I have never thought "I wish my gears werent so deep".

I've been there in my hot rodding days.. 350TH and get 4.10's they said.. speed off the line! Yeah, 60mph and revving at 3000 sucks. lol

 

[cal]

I've been there in my hot rodding days.. 350TH and get 4.10's they said.. speed off the line! Yeah, 60mph and revving at 3000 sucks. lol

The problem wasnt the gears, it was your lack of 700R4.

 

[Levathain]

Well I think people are ok with it because that's all it is is ok. I mean don't get me wrong it's better than 3.55 gears but it's not enough. Before going up a semi steep incline on highway id have to downshift to
Keep up speed n now I don't n in town is better get up n go. But if you are spending 1300 why have average power, there also is nothing on my xj except a lift. If my jeep was weighted down with gear it would be shitty or if I was hauling.