chadrenner69

i was wondering how much regearing my jeep would be for the front and rear diff.
i have 32's on it too what ration would make the best gas milage difference

xjmarc

You can get gear packages for around $350 but installation can run you a bit more than that depending on the shop. Depending on what axles you have and what ratio you plan to go to you may need new carriers as well. Call around a few local shop and get some prices, talk shop(like fav wheeling spots) with 4x shops and you tend to get a better deal.

96_xj

you want 4.10's for a manual tranny. or you could just stay with your 3.07's like me and basically have a 4 speed lol. (i have 33's tho)

tuxfan212

Off topic but I have a manual and p235s. I have 3.07 gears with a 8.25 in the rear. If I put bigger tires and a lift on why would I need to change my gearing??

96_xj

okay so i will see if i can scrounge up the last thread i was typing on a while back, but the gearing is designed to keep the engine in an RPM range at certain speeds in certain tranny gears.
(found it)

for example:
i will put some comparison at freeway RPM's and MPH for both gear sets using a 28" (stock) and a 31" tire on both gear ratios(in 5th gear)

Gear ratios for the AX15 are: 3.83, 2.33, 1.44, 1.00, 0.79


3.07's with 28" tire:
55: 1600rpm
65: 1891
75: 2182
85: 2473

3.55's with 28" tire
55: 1850
65: 2187
75: 2524
85: 2860


3.07's with 31" tire:
55: 1445
65: 1708
75: 1971
85: 2234


3.55's with 31" tire
55: 1671
65: 1975
75: 2279
85: 2583



so as you can see if you have the stock tires and 3.55's your RPMS's are nearing the 3000 mark for cruising at 85mph (which is about what we can travel here in nm on the freeways) and that will drop your fuel economy-bad. 2500rpms for 75 is not to bad(it is what i travel at in 4th gear with my 33's and 3.07's) but you will notice a drop in fuel economy. However when you switch to 31's it will be close to stock, and still give you a bit of a better pull in 1st and 2nd with the same fuel economy you have now.

one last thing you need to look into is that your speedo will be off if you run on the stock tires until you get your 31's. i will see if i can find the calculations to make it correct.


SO its all a ratio game. You want to try to stay within the stock ratio. thats why you regear. so you can keep all of your power and torque bands in the stock range.

With my 33" tires and 3.07 gearing my 5 speed AX-15 is basically a 4 speed. when i go into 5th it drops the RPMS down to 1700 and since i am not in the power band of the motor it keeps dropping and dropping until about 60 mph and thats all i can get out of the motor. I have to cruise in 4th gear-hurting fuel economy and keeping my engine RPMS higher than i would like. but it works for me as i have no problems with it right now but thats why you re gear. sorry for the long post and any grammatical errors or redundancy lol

tuxfan212

Thanks alot very informative. The only thing is something has to give when you regear. Do you lose torque or a top speed or what.

rockhound23

I've got an automatic, 8.25 with 4.56's running 33's...you'll gain a lot more torque and pickup, ever so slightly raise you RPM range. Biggest difference is the upshift and in/out of overdrive for me. I've noticed big time improvement in the shift points (quicker shifts ...no more 3000 RPMs to go from gear to gear).

Only thing is the speedo will be off unless you change the speedo gear in the transfercase...not hard to do, but a little expensive for what you have to buy. I'm sure there are aftermarkets available, but bought mine from Jeep stealership for like $65 dollars for a plastic gear!!!

96_xj

your ONLY losing something if you DONT regear! the reason you DO regear is so that you DONT lose anything from adding the big lift and tires! you might lose a little bit of gas mileage but thats about it and it wou=nt be much most of the time =]

offroadnut36

x2 on the 4.10s