BenBru23

ok i am trying to figure out this checking your gear ratio by jacking up one tire and counting rotations i have 33 inch tires will this work still with that big of a tire need the run down on correct way of doing this thanks

trapper

It would seem to me that the data out there would be specific to stock tire size.. I dont know for sure.

There should be a tag on the axle and/or pulling the dif. cover and counting the gears is your best bet.

Chances are you would benefit from a visual wear inspection, reseal w/new gasket and new fluid, anyway.

Also, if its stock:
http://jeephorizons.com/tech/xjstockspecs.html
http://www.grimmjeeper.com/gears.html
will both help.


good luck,

BenBru23

i have really bad luck with getting things to reseal properly for me haha. i was trying to tip toe around pulling the diff cover off. its a 91 I6 5 speed bought it with some upgrades lift tires tc drop just wondering if the guy put in gears or not my speedo reads 45 mph when the jeep is cruizin at 60 mph i have always been told 33's would only make the speedo off about 7 mph not 15!

Mike H.

I assume you are rotating the tire once and counting how many times the driveshaft rotates... you could have 54" tires on there and it will be the same, you are still only rotating the axle 1 revolution.

A speedometer is never off by a fixed mph, it is a ratio... aka %, faster you go the more mph it is off by.

BenBru23

yes counting the driveshaft revolutions i spin the tire one full revolution and the end cap that i mark is only rotating one and a quarter turn

BenBru23

i would really like to get this figured out today anyone know what im doing wrong im marking the tire on the tread for showing a full revolution should i mark somewhere esle whats my problem?

trapper

the faster you go the wider the variance..

my DD is a 2004 Chevy 2500HD with the factory 2 inch lift.. I increased the tire size and turned up the torsion bars slightly to level the truck (snow plow on it).. and the spedo didnt seem off until I got on the freeway. I havent had a ticket on years.. but I got 2 in 1 week after the tire change!!!!

On the freeway though my spedo read under 70 and I was tagged at 83!

This being the case.. you SHOULD be traveling faster than what the spedo reads.. not the other way around (as in your case - if I read it right).

leads me to think that the prior owner had larger tires on it and reduced the size to sell.. but that is dramatic difference.. I would get some Black RTV and reseal anyway.. with a newer truck to you and a tell tail sign that things were all changed up.. inspect the gears for wear.. tighten the bolts back down in a star pattern with a small bead of RTV toward the outside of the seal .. you will be fine (that stuff goes a long way) Its also called liquid gasket..

good luck

BenBru23

no my speedo is reading slower than what im actually going i was told though that 33 inch tires would only make it read 7 mph slower than what im actually going but the speedo in reality is reading 15 mph slower that the speed the jeep is actually going.

posjeepxj

im guna take a gues but if you have the i6 and the 5speed im pretty sure its the 3.07 gear

BenBru23

whats your thoughts on the 3.07 gears?

posjeepxj

you need 3.73s would put you 5% under stock and 4.10s would put you 10% over. I am working on gearing myself so i am doing research so i am am tring to remember what i have read the last few days.

only difference between me and most people when it comes to gearing is i am shooting for more mpgs. i have 33s and the aw4 on my dd/ weekend wheeler

Cherokee

well with bigger tires you lose power with smaller gears.

the 3.07 came stock with 5 speeds, so if the PO didnt change them, thats what they are.

posjeepxj

easy way to check that. look and the dif cover and see if there is any rtv seleant. If there is none you know it was never changed. if there is some someone has done something (either changed fluid or changed parts). Pull it off if you saw sealeant and count the ring and pinion teeth.

It will be a good thing cause you will be putting fresh fluid in there, alot of people never change fluid

suburban_sam

http://jeephorizons.com/tech/rpmchart.html

This chart should help you get a good idea of your gear ratio without opening the diff. Hope it helps.

Iant333

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