im running 3.73s with my 3 speed and 33s and its fine.  so far i cant justify changing gears.  but if i was to change gears with my auto i wouldnt go lower then a 4.10 due to not having a OD  

yeah rawkon, thats about where I was going with the tranny Q, already knowing he has 3:07's I'm assuming it's also a auto. at 65 it'll be cranking out 2700 rpms with 4:10's, your 3:73's should be around 2450. for a daily driver I'd probably go with the 3:73 myself, and is nearly enough to campensate for the 33's, the 3:07 and 30" tires figures to be about 2250 rpm @65.

for the ax-15 I wouldn't hesitate to run the 4:56's.

the 32rh (tf999) has a 1st gear of 2.74, so It can still get moving easily with high gears.  

Rawkon:
im running 3.73s with my 3 speed and 33s and its fine.  so far i cant justify changing gears.  but if i was to change gears with my auto i wouldnt go lower then a 4.10 due to not having a OD

Well when you consider that stock tires are around 29, you have about a 15% ground power/tractive effort loss with 33's and 15% more tranny strain in every mode of operation (actually more because of extra drag) I do not know why some many are afraid of a few extra RPM as it will not hurt anything and actually extend its life because the cylinder pressure and rod bearing loading will be less because less torque is required with deeper gears. The funny part is that user install big tires and lift to make their 4x4's "bad" but they do not do the gear swap to go with it and have a "bad" 4x4 with less pulling/tractive effort power than a stock one. Myself I would never even remotely consider a lift and tires size increase without a gear swap. BTW, long long ago in early 70's I had a 66 3/4 ton chevy with a 4.57 rear axle and a 4 speed and a 250. It ran well and was no worse the wear for it and I even towed a car on a trailer to NC with it once (over 400 miles) with no problem keeping speed either on hills. It used to get about 15 empty and 11 to 12 towing on road which was not bad for size and weight of truck. Had it had taller gears it would have been a slug and MPG would have likely suffered too. There was a time when a 1/2 ton 4x4 came with 4.10 gears, a 3/4 ton with 4.56/4.57 (4.57 was GM then) and 5.13 with 1 ton and there was not OD then either. I consider 4.10 gears with 31's as the "standard" in a 4x4 and with tires size increase, deeper yet gears. I like them to run well too.  

That was alot of info, thanks. My jeep has a manual transmition and I opted for 4.10 because I was looking at 4wheel parts' gear ratio to tire size chart and found that 4.10s would be right in the middle range of good fuel and good power. I also didn't want my engine to be running at too high rpm but after getting help here it seems it wouldn't be bad to run the lower gears. Right now at 65, rpm hits right on the chart with 3.07 gears would 3000 rpm be safe at 65 mph constant. Oh, yeah and the oil is 10w/30 and the problem was oil pres was rising to the 80s at 65 then it'll decrease to 50s after warming up on 5 min drive.
You know I want to do the gear maint myself could I get the backlash limits, thanks and I'm just gonna change the bearings and seals for now. I agree no sence in having the work done twice. I'll save up and then get bigger gears and a locker front/rear for more fun. hopefully soon  

Not sure how you are doing your math. 3.07 gears with 33's and a AX15 yields about 1600 RPM at 65 MPH in 5th. (too tall big time) 4.10's would yield about 2100 RPM and a 4.56 would yield about only about 2350. When yo do the math to select a gear ratio you must remember that vehicles do not operate in a "vacuum" and with bigger tires and lift it takes more HP to cruise than before at any given speed and this HP is gained through increased RPM (HP equals torque x RPM divided by 5252) Furthermore, while some seem to think lower RPM always equal better MPG, such is not the case when engine starts to labor as it has to work harder to make needed HP at a lower RPM. Generally you want a manifold pressure of about 10 inches or lower (lower meaning less pressure meaning like 11 or 12 inches of vacuum and so on) for best economy as it means engine is not laboring much to produce needed cruise power. As far as setting up gears, there is more to it than just setting backlash. More importantly there is bearing preload and gear mesh pattern which you confirm with gear paint. You need to get that part right if you want long gear life and quiet operation. Backlash is the last thing you check AFTER you get preload and mesh right. BTW, below is a link to a online axle ratio/tires size calculator. Feel free to use it as much as you want.

Click Here  

4:56 will be the best choice beings you have a ax-15, the 4:10's wil not satisfy you at all especially with 33's.........take advantage of that 5th gear instead of being stuck in between 4th and 5th all the time. 4:10's are great for 31's it'll be a turd with 33's. the fuel economy will also be greater using 4:56's.

if you spend a lot of time in traffic or don't have much highspeed driving in your commute seriously think about 4:88's.

this was brought to you by......Been There, Done That.  

missed something there.....the chart you may be using probably fails to recognize the .78 5th gear your ax-15 has. the reason I say that is a 3spd auto (1 to 1) will run 3,000rpm @65 with 4:56 and 33's

the 5spd ax-15 (.78 to 1) will turn 2,350 @ 65 like snoman said........that's what you need.

using 4:88's, 33" tires @65 you'll be turning 2500rpm even a 5:38 is 2700rpm.

I'll stand by the 4:56's and the 4:88's for excellent power and economy.
*******************************************************
I'm running 4:88's with 34's, this summer it will be getting 5:38's installed, my OD is .69 to 1 and the 4:88's aren't enough for me. even that combo in my rubi is is a little over 2350 @ 65mph turning 34's. (5:38's)  

chamoru:
That was alot of info, thanks. My jeep has a manual transmition and I opted for 4.10 because I was looking at 4wheel parts' gear ratio to tire size chart and found that 4.10s would be right in the middle range of good fuel and good power. I also didn't want my engine to be running at too high rpm but after getting help here it seems it wouldn't be bad to run the lower gears. Right now at 65, rpm hits right on the chart with 3.07 gears would 3000 rpm be safe at 65 mph constant. Oh, yeah and the oil is 10w/30 and the problem was oil pres was rising to the 80s at 65 then it'll decrease to 50s after warming up on 5 min drive.
You know I want to do the gear maint myself could I get the backlash limits, thanks and I'm just gonna change the bearings and seals for now. I agree no sence in having the work done twice. I'll save up and then get bigger gears and a locker front/rear for more fun. hopefully soon

on another thread i mentioned this chart and was asked to produce it. i have been unable to find it. could you post it for me?  

chamoru:
That was alot of info, thanks. My jeep has a manual transmition and I opted for 4.10 because I was looking at 4wheel parts' gear ratio to tire size chart and found that 4.10s would be right in the middle range of good fuel and good power. I also didn't want my engine to be running at too high rpm but after getting help here it seems it wouldn't be bad to run the lower gears. Right now at 65, rpm hits right on the chart with 3.07 gears would 3000 rpm be safe at 65 mph constant. Oh, yeah and the oil is 10w/30 and the problem was oil pres was rising to the 80s at 65 then it'll decrease to 50s after warming up on 5 min drive.
You know I want to do the gear maint myself could I get the backlash limits, thanks and I'm just gonna change the bearings and seals for now. I agree no sence in having the work done twice. I'll save up and then get bigger gears and a locker front/rear for more fun. hopefully soon

chopperfreak2k1:
on another thread i mentioned this chart and was asked to produce it. i have been unable to find it. could you post it for me?

when using such charts you need to be aware of the final drive ratios.
some are 1 to 1
some are .69
some are .7
some are .73, .75...........ect.

the charts aren't a reliable source for OD trannies unless they specify what they are.  

i know the chart he is talkin about just cant find it among all my other crap. it only takes into account your stock gear and tire size, then tells you what gears you need as tire size increases. it does work, as it's goal is to get you back to stock performance once you start running bigger tires. it is not meant to tell you what gears are best for X driving conditions. it only gets you back to stock performance.  

chopperfreak2k1:
i know the chart he is talkin about just cant find it among all my other crap. it only takes into account your stock gear and tire size, then tells you what gears you need as tire size increases. it does work, as it's goal is to get you back to stock performance once you start running bigger tires. it is not meant to tell you what gears are best for X driving conditions. it only gets you back to stock performance.

gear ratio and tire size chart

as I mentioned, the chart is not correct for a OD tranny, and can be misleading for those who don't understand the difference in 1 to 1 ratio's and a .69 to 1 final ratio. which is a huge difference.  

well ok but explain to me how it does not work for OD trannys  

the chart figures the rpm and speed at a 1 to 1 ratio, the ax-15 is .78 to 1 ratio,
sooooo, Its 800rpms off which can lead to getting the incorect ratio for the application..if it's not understood.

If the jeep had the 3spd automatic the chart is absolutely correct.  

Here is that link to that chart.
http://www.4wheelparts.com/gear_ratio.html

Wow, everything is starting to get complicated with the addition of the transmision. Well, for now I'm gonna use 4.11 because I found a set at a lot. Used but in good condition. I do plan on upgrading to bigger and getting a LSD or locker. Thats later thow.  

hello i have a 97 tj that i have been stock pileing parts for over a year im a solger deployed to Iraq I was going to order gears for the jeep 4:88s the tj SE with a four cyl has the dana 35 rear and the 30 frount right ? and i was alos told i would need a new carrier for the dana 30 is this true if so whear can i find the right one ?  will 4:88's work good with 35's ? I'll be home in 2 months to buld the jeep. thank you for your info