mopar440

Seeing alot of posts about "what gears to use", yada-yada... here's an easy to use, but in depth calculator to help figure out what gears to use with whaht tire size, and can help figure out what happens when you change things like trans and xfer cases... plug in the numbers, compare readings... thing to remember is do a BASELINE! Punch in stock everything, incl. tire size, and TAKE NOTE OF RPMs AT A GIVEN SPEED!!! Trick is to end up with the same RPMs at those given speeds (as close as possible) for the best mileage/throttle response as stock...

Play with it a little, learn how to use it... my set up tells me I need to regear to 4:10s... AW4/NP242/3.55/215-75-15 ... now have 31" tire... 4:10s will put my RPMs back as close to stock as poss. and restore mileage/power...

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

tannerp89

your a god among Jeepers, thank you!
it still tells me to go with 4.56's with my 32's to get back to stock, well as close as i can get.(AW4/NP231/3.55/215x75/R15)

xjoffroad

thanks! people, just a simple google search you will find numerous calculators for you. its not that hard.

yes 4.56 will get you back into the stock rpm range. have no clue why people are telling you to go with 4.10's............

mopar440

You're welcome! And glad you figured it out... it's not really rocket science, but some guys have a hard time with numbers, so thought I'd post this to help out

tannerp89

lol no not rocket science but i JUST started messing with gears and whatnot and am not real familiar with the math required to figure this crap out.

tannerp89

and i have no idea either. everyone i see with 32's/33's runs 4.56's.....
do you think ill have issues with my D30 gearing it out as far as breaking shafts n whatnot?

xjoffroad

you are regearing the d30 also right? Kinda confused me there for a second. just remember its a d30 and you will be fine. i wheel with a lot of d30's that are locked and 4.56 or 4.88 gears. if you are really wheeling it you will break shafts from time to time but its a shaft and it takes 20min to replace. carry spares!

tannerp89

lol ya regearing my D30 and Chryco 8.25 to 4.56's, and my D30 is locked also. and ya i will have to go get some spares then! pull n save here i come!!!

xjoffroad

pull the shaft with the unit bearings hubs. then all you have to do when you break one it unbolt the 4 bolts that hold the hub on and install your complete other set! 20 min and you are done

tannerp89

good idea! and thought it was 3 bolts.....
wouldnt you want new hubs and u joints in the shafts though?
and we need go wheelin' some time.....Everett isnt that far from me....

xjoffroad

i think you are right about the 3 bolts. my bad. my spares are what I found at pull a part. same with the hubs. I would put new hubs and ujoints in a spare shaft. maybe keep a spare set with new hubs and ujoints at home if your xj is a dd.

tannerp89

i think ill get two sets of spares and do one set up with new hubs/u joints foe extras and keep the others as trail spares, cause it is my DD...for now

djb383

Here's the math I used:

215mm X .75 X 2 / 25.4mm + 15" = 27.7" stock tire diameter and presume 3.55 stock diff ratio

32" dia tire / 27.7" dia tire = 1.155

1.155 X 3.55 = 4.10

rweaver138

3 bolts

xjoffroad

good thing i said this