In my quest to identify my gear ratios for my 96 ZJ so I could match new tire size and gear ratio's correctly, I happened across these calculators. They may have been posted here before but searching the sight I never found one this simple. If I got this in the wrong spot I trust someone will correct it.

Looks like I'll be rolling on 33's with 4.30 gears, Dana 30 up front and Dane 35 rear with 30 spline chromoly axles and lockers. The calculator punched out a 4.11 ratio but I bumped it up to 4.30 to increase RPM 5% for a fraction more power at the wheels.

http://www.crawlpedia.com/calculators.htm

This is the calculator page but if you click on "full calculator" under the category it gives you a lot more pertinent info.
Hope this helps guys...

 

The problem with that is that they don't make 4.30 gears. They make 4.27s for D30s, but not Dana 35s. So you will have to choose between 4.11 and 4.56

 

I see that. So the plot still thickens...LOL 4.11 would keep RPM's the same, 4.56 would be 10% Hmmmmm. For me, even though I would like the extra RPM, I think the extra strength of the 4.11 may be the way to go but I'm open to other trains of thought...

 

4.11 is popular. Your biggest strength issue is with the axle shafts. The C clips on them can fail. Fortunately you have rear disc brakes so you won't spit the shaft out

 

Do you want to know the formula that that website uses to calculate everything?
RPM=speed × transmission gear ratio × axle gear ratio × 336 ÷ tire size. You can figure it all out yourself using that formula.

 

Here is a better one http://www.grimmjeeper.com/gears.html

 

That one is the best

 

I've seen this chart before and my eyes glazed over. I swear I didn't see the drop down menus. I swapped out my 249 Transfer Case for a 242 and a slip yoke eliminator. They both have a 272 ratio so that shouldn't make a difference. Plugging them in with a 4.11 ring and pinion and 33's would give me identical RPM's at 10,30 and 70mph as stock. The 4.56 would bump the RPM's up right at 10%. I think I like the 10% adder and as of now will be going with the 4.56 ring and pinions and 33's

 

Your butt dyno will like that

 

?????

 

the feel of more power

 

I used to like straight-line G force until I got addicted to lateral G force. Now it's that kick in your spine when the spinning stops and you grab something!

 

4.56 gears are good. you also need to consider the higher ride hight with a lift (push more air), armor you may have installed, and any cargo you plan to carry. so even though 4.56 carries slightly higher RPMs those things mentioned above will work against you.

 

Jon, seems like you have pretty close the same setup. I went with a 4" RC long arm lift and a new thermal fan clutch. I'm shopping my Dana 30 & 35 hardware now. How's your setup working for you? My theory is a little more RPM gets you a little closer to a better torque range for pulling, climbing getting through mud. When the bumpers, winch, sliders, fuel cell armor and wench are installed I'm guessing I'll probably be adding 500-600lbs. then cargo? My 4" lift may be down to 2" by then and I may have to cut weight and leave the wench at home...
...

 

IDK about your ZJ, but I've put 1500 lbs in my stock, cheap WJ Laredo and it still has spring action left! It only looks slightly low, my headlights are a little high, and braking is a little late, but it seems to handle the weight like it was designed for it. Although, this might be the reason my rear axle blew up!