Tire Size and Gear Ratio

[cher96]

Here is a URL for several Gear and Tire Calculations:

http://www.dirtroad.com/gears.htm

Here is a pretty accurate Chart for Gear Ratios and Tire Sizes for Jeeps:

http://i41.tinypic.com/2ahsfab.jpg

Citation: http://www.jeep4x4center.com/jeep-tires/tire-gear-ratio-chart.htm


Disclaimer: I forgot that when I posted that I do fine with 32" Tires and 3.55 Gears that I have Heavily Modified my XJ and more than likely I have much more Torque and Horsepower than a Stock XJ.

[Voldemort]

Very cool I have seen this before and lost it thanks. I think the 4.88 is a great gear for 33" to 37"

[Mudderoy]

With my automatic, 4.56 gears and BFG 32 MT I get 3000 rpm at 80 mph.

This chart may not take into account overdrive.

[cher96]

Here is another Tire Size and Gear Ratio Chart for Jeeps. You can see why I would run 4.11s with 33s and I have great Economy with 32s and 3.55s. I like Low End Torque and almost never go over 2500 RPM. This Chart differs, I believe, because it assumes you are in 4th gear with a 1:1 ratio whereas an XJ's AW4 in 4th gear is 1:0.75

http://i41.tinypic.com/30a6dr8.jpg

Citation: http://www.nakedjeep.com/Knowledge/Math/njGearChart.html

[N1TZU]

This is also great imfo to have on hand cher96, Thank you..........

[jimwww]

I am running 3.73 with 33x12.5 and I also have an auto tranny - it has a button on the dash that does the pwer vs comfort and that button does work. Not sure what it does but on -power- it works much better. I think it is fine to drive around with those gear ratios and such - what worries me is the brakes. (no emerg stopping for me)

[d0nt_h8]

I'm running 35's w/4.56 gears. I run in low to 60, then shift up. I'm usually around 2500 @ 70 or so. Nice & smooth =-)

[modestmar00xj]

thanks for the information, very helpful!

[GreenXJosh]

Nice. Very helpful.
I am curious if these charts apply to both AW4 and AX15? Does it make a big difference?

[LizardRunner]

Nice. Very helpful.
I am curious if these charts apply to both AW4 and AX15? Does it make a big difference?

The AX15 has a fourth gear ratio of 1:1, fifth is like fourth in the AW4 1:.075

[LizardRunner]

I am running 3.73 with 33x12.5 and I also have an auto tranny - it has a button on the dash that does the pwer vs comfort and that button does work. Not sure what it does but on -power- it works much better. I think it is fine to drive around with those gear ratios and such - what worries me is the brakes. (no emerg stopping for me)

That button should switch you to hard shift (on) or soft shift (off).
the way this feature usually works is to change the shift point rpms. Sorta like having two different torque converters in one.

[Skater28]

Hi is this chart with an automatic and what speed is the rpm based on. I have a 94 XJ auto with 33s. what would be the rpm at 65 mph. Thanks

[Mudderoy]

Hi is this chart with an automatic and what speed is the rpm based on. I have a 94 XJ auto with 33s. what would be the rpm at 65 mph. Thanks

If you notice it says 4th gear. So if it is for an automatic, and I believe it is, it doesn't take into account the 5th gear, which is overdrive. This chart doesn't address speed just tire diameter, great ratio and RPM.

[Weldmen]

I believe automatics are 3 speeds and the 4th would be OD.

[4.3LXJ]

Unless otherwise stated, most gear charts assume a 1:1 final ratio.

[Mudderoy]

I believe automatics are 3 speeds and the 4th would be OD.

Hmmm my post is just way off. So is my RPM, I get 3000 rpm at 80 mph and I have 32" tires and 4.56 gears.

[jeepxj95]

take ur rpm and times it by ur overdrive is what u guys are looking for
example 31in tires and 3.55 gears = 2500 ish rpm times by .75 = 1800 ish rpms in overdrive. hopes this helps u guys

[honesT]

Dam those #`s are high. I have an automatic 96 XJ with stock 225 75R15 tires only mod I have done is Highflow cat & muffler to increased MPG (save gas) as it shifts into OD sooner.
@ 71 KMPH I`m at 1250 RPMS and at 80 KMPH it`s 1500 RPMS. After these readings I hacked the front off of my air intake box and found it made a noticable difference in the smoothness of my engine and gear changing but nothing noticable on the rpm scale. Not sure if it`s good for everyone`s trails but works great for a DD.

I`m still on the wire about the gears, I have heard people running 35`s with stock gears and no problems so Maybe it`s what kind of abuse you are going to put your gears & tranny through that really matters?

Stock 3.55 gears, HWY 31`s trail 35`s ????????

[4.3LXJ]

Run 35s on stock gears? Possible yes, but advisable no. It would work well in a dedicated mud rig, but not otherwise advisable, particularly for highway use.

[bluedragon436]

I don't think I'd go 35's on the stock gears.. I think I'll stick with my 33's on the stock gears until I can afford to pick up some gears as well as a locker to install at the same time..

[bigjim350]

I am planning on running 35's on my stock gears for a while. However mine is mostly a trail rig, and I know it will never come out of 4lo with those tires on it. Not that it does with the 33's

[willtodo]

FYI,,,,, 410s with 33s put me 200 rpms at 55mph higher than stock 355 and stock tires,,,,,,,,,,in other words it corrected the speedometer within 2mph ,,, giving me 200 more rpms for loss of torque,,,,,456 would have made about a 500rpm differance ,,,,

[Mudderoy]

FYI,,,,, 410s with 33s put me 200 rpms at 55mph higher than stock 355 and stock tires,,,,,,,,,,in other words it corrected the speedometer within 2mph ,,, giving me 200 more rpms for loss of torque,,,,,456 would have made about a 500rpm differance ,,,,

Corrected the speedometer? There maybe a gear/tire combo that matches the 3.55/27 inch tire but to get the speedo right I think you really should change out the speedo gear in the transfer case. I guess some people don't really care, but I like having the speed right, for mpg calculations, and every time I see a cop. :thumbsup:

[TUWdave]

This link is very helpful for selecting different tire diameters, gear ratios, speeds and rpm with different tire size and gear ratio combinations.
http://www.novak-adapt.com/knowledge/gearing.htm
Later............
Dave

[EGJeep]

I have a 2000 XJ bone stock. I want to upgrade to a locker, but haven't decided which brand or which axle yet. How do I know what gear ratio I have? I under stand some came with LS in the rear, but my 8.25 chrys is open. How do I find the gear ratios for both front and rear? :confused:

[4.3LXJ]

Here ya go. This is for a front, but the back will be the same

[XJ Wheeler]

Here ya go. This is for a front, but the back will be the same

Nothings showing up Steve.

But there should be a tag under one of the bolts on either the front or rear diffs noting the ratio.

[4.3LXJ]

Oops, forgot the link

http://www.xjtalk.com/showthread.php?t=13203

[SteveMongr]

I run in very deep, soft, and rutted sand. Large amounts of torque are needed.
31" tires is where re-gearing begins. Otherwise you will need to run 4-low.
3.55 and 31"s is fine for mallcrawling but not the desert.