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31's with 3.55's?

Not really. I did for a couple years. Not really worth the time or money to get 3.73's or 4.10's. Especially on a DD. Speedo should be off roughly 11% depending on what tires u get and it'll feel a little less peppy but other than that it's fine.
 
I have a manual transmission, so mine started at 31's on 3.08's. I plugged some 3.55's a friend gave me in when he went went to 4.88's. A little lower crawl ratio would be nice but it works pretty good and doest great on the interstate. When I can afford it, I'm going to swap in some 4.10's and ARB's hopefully and make a camping rig out of it.
 
I run 3.55's and 31's but there are a lot of factors that come into play, and one of them is weight

Personally I hate this combo, acceleration sucks in the city, I drive around in 3rd in the city and on the highway. Once I reach 70kph speed limit (44ish mph) it cruises great at that speed at around 1800rpm in town. If I get out on a country road and OD kicks in at 80kph my rpm's drop to 1400 (actually a little less) and the thing is a slug! It's too low even at the 100kph speed limit and the truck slugs along and drives like shit. Hence why I stay in 3rd ALL THE TIME.

I run true sized 31" MT's and cragar soft 8's which are an incredibly heavy thick gauge steel.

My speedo was incorrect from the factory. I have verified via GPS and my speedo is dead on now with 3.55's and 31's

I average 190ish miles out of a tank of fuel... I plan to regear REAL soon

My XJ is a 1996 if that makes any difference?
Don't believe all the speedo is off posts until you verify it for yourself with GPS. I didn't think I was getting that piss poor mileage until I found out the truth from my buddies Garmin Nuvi.
 
I have 31" MTR's on my '01 with 3.55's. I don't much like it. My Jeep is a work in progress and gearing is near the top of the list. I live in the mountains and the difference from 235/75 15's to the 245/75 16's is very, very noticeable. I can live with it but I don't like it. I'm gonna go 4:10's when I can.
 
I have 3.55 and 31x10.50 MTRs.

With the AW4 slushbox I think it sucks. It has been a couple of years that way so it can be done... and it does work OK

On the Michigan hills. it regularly shifts down at freeway speeds. I run in 4Lo on the trail and I still sometimes grab gears on hill climbs.

I am in process of going 4.88 now... The d30 is done with ARB, D44 is getting disks then ARB and 4.88's I do plan going up to 33-35 inch tires. Likely will be on 31's and 4.88 for a couple of years....

Jeff
 
Dayamn... I dunno how you guys don't have any power with just 31's. They're not that big, you shouldn't have to keep it in third all the time and I've never had any trouble with power on any trails. If that's the case then maybe you need some motor work?
 
Yea, if you don't have any major motor problems, you won't have any trouble daily drivin the thing. I was still able to embarass some civics w/my 31's lol. Not to mention 4lo for the trails.
 
The '97 4.0 had 190 HP and 225 ft pounds of torque

Actually my Cherokee had 27 inch tires so when I moved to 31's I was actually moving up 13%. The 31's are about 13% larger than my stocker tires thus your performance will also drop by about 13%....If you knock 13% off the peak HP and you get 165HP and 196 ft pounds. Yea, I know that it is not a perfect linear relationship but it works to ball park it.

Yea we can notice it Add in effects of the extra wind resistance due to lift and higher profile you should notice it when pulling a hill, or a trailer. Not that it is an impossible combo but you do notice it.

At 10-13% it is on the fringe.. Yea you can do it, but you also should notice it.
 
PurpleCherokee said:
Dayamn... I dunno how you guys don't have any power with just 31's. They're not that big, you shouldn't have to keep it in third all the time and I've never had any trouble with power on any trails. If that's the case then maybe you need some motor work?
Click to expand...

Yeah I was going to say when i had 31's on my 4.0 HO I could scoot around town real peppy and what not and my 33's are fine too! Maybe it's just the HO
 
vortex said:
Wait are you saying that 245's are 31'? if so then 265 would be 33's? Maybe i just read it wrong.

-PJ-
Click to expand...

If you notice he said it was a 245/75R16 and that does roughly equal a 31. Most 245's are between 30.7" and 30.9" tall. Which is actually taller than most 31/10.50R15. Actually a 265/70R16 is the exact same 30.5" tall and 10.5" wide just like most 31" flotation tires. In the 16 inch metric sizes a 265/75R16 is 31.8" tall and 10.50" wide. The 285/75R16 is 32.7" tall and 11.5" wide. The 305/70R16 is basically the same as a 33/12.50R15.

The only down side to the metric sizes is the load range. It is hard to find anything larger than a 245 below a D load range.
 
I just blew one of the 255/60/15 Yokos and they no longer make that size(didn't pay tirerack the road hazard either). I didn't know what happened at first, but heard a noise in the rear(whatever punctured the tire was spit back out and hit the well). I was doing 70 in the fast lane on the beltway and it took me 1/2 mile before I pulled over due to knowing something was drastically wrong. Needless to say a simple plug won't fix the bubbly/internally separated sidewalls.
 
JAS said:
Yea we can notice it Add in effects of the extra wind resistance due to lift and higher profile you should notice it when pulling a hill, or a trailer. Not that it is an impossible combo but you do notice it.

At 10-13% it is on the fringe.. Yea you can do it, but you also should notice it.
Click to expand...

If were talking about aerodynamics then its already outta the picture...we are driving BOXES down the highway!!!! So I'm not worried about gas mileage or aerodynamics.

-PJ-
 
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