30X9.5s Vs. 31X10.5s

Im going to go with a 3" lift. And I am stuck between 30s and 31s. I have a 1990 MJ with the 4.0 and AX-15. With 3.07 gears.

I know its not a Econobox or a racecar, but I like to play sometimes and I dont like the gas station. I know they dont get great mileage, but I dont want to kill it.

Will there be any significant differences between the 30s and 31s? Am I just being stupid thinking there will be?

there is a one inch height difference and a one inch width difference HTH:thumbup: goodluck man

31's with 3.07's suck on a stick shift. Even 30's should have more gear, but you can live with them. Don't expect sparkling performance with either.

Im thinking of swapping to 3.73s in the future for some extra gear. But probably when I happen to find a killer deal.

31s with 3.07s SUCK. Go with the 31s but regear to 4.10s if your sticking with 31s.

Think 4.10s might be a bit deep for 31s?

AX-15, 31s with 3.07s

Gear Mph per 1000 RPM Mph @5000 RPM
----------------------------------------
1 7.84 39
2 12.89 64
3 20.86 104
4 30.04 150
5 39.53 198

Mph RPM (in Gears)
-------------------------------------------------
1 2 3 4 5
-------------------------------------------------
5 637 388 240 166 126
10 1275 776 479 333 253
15 1912 1163 719 499 379
20 2550 1551 959 666 506
25 3187 1939 1198 832 632
30 3825 2327 1438 999 759
35 4462 2715 1678 1165 885
40 3102 1917 1332 1012
45 3490 2157 1498 1138
50 3878 2397 1664 1265
55 4266 2636 1831 1391
60 4654 2876 1997 1518
65 3116 2164 1644
70 3355 2330 1771
75 3595 2497 1897
80 3835 2663 2024
85 4074 2829 2150
90 4314 2996 2277
95 4554 3162 2403
100 4794 3329 2530
105 3495 2656
110 3662 2783
115 3828 2909
120 3995 3036
Removed after 120 for space

Gear Change RPM drop (change @5000)
---------------------------------------
1 -> 2 -1958 (to 3042)
2 -> 3 -1910 (to 3090)
3 -> 4 -1528 (to 3472)
4 -> 5 -1200 (to 3800)



With 4.10s

Gear Mph per 1000 RPM Mph @5000 RPM
----------------------------------------
1 5.87 29
2 9.65 48
3 15.62 78
4 22.49 112
5 29.60 148

Mph RPM (in Gears)
-------------------------------------------------
1 2 3 4 5
-------------------------------------------------
5 851 518 320 222 169
10 1703 1036 640 445 338
15 2554 1554 960 667 507
20 3405 2072 1280 889 676
25 4257 2590 1600 1111 845
30 3108 1921 1334 1014
35 3625 2241 1556 1183
40 4143 2561 1778 1351
45 4661 2881 2001 1520
50 3201 2223 1689
55 3521 2445 1858
60 3841 2667 2027
65 4161 2890 2196
70 4481 3112 2365
75 4801 3334 2534
80 3557 2703
85 3779 2872
90 4001 3041
95 4223 3210
100 4446 3379
105 4668 3548
110 4890 3717
115 3886
120 4054

Gear Change RPM drop (change @5000)
---------------------------------------
1 -> 2 -1958 (to 3042)
2 -> 3 -1910 (to 3090)
3 -> 4 -1528 (to 3472)
4 -> 5 -1200 (to 3800)



4.10s would be fun, but I think its a little overboard for a DD. 3.40 puts me close to stock, 3.73s for a bit more.

Do dana 35s have a carrier split?

3.73s will be a waste of cash.

There are many threads on this, but they all come to the conclusion that the 4.10s are perfect for 31s, and even 30s.

I run 30s and 4.10s and get 15 in the city and 20 on the highway, and am not always easy on the gas.

Fergie

Reason I wanted 3.73s is that they would be a lot easier to find on Junkyard rigs.

Are 4.10s really my best bet for 31s? I figured that it would be too deep and I would end up running too many RPM. Most of my driving will be in the 50mph range on backroads. And the occasional (about every weekend in the winter, snowmobiling) trip 3 hours on the highway.

Take it from myself, and MANY others.....YOU WILL REGRET 3.73s!! GET THE 4.10s!!

Honestly, do a search and you will find many threads stating my exact sentiments.

Fergie

EDIT: THe 4.0L likes to run in the 24-3200 rpm range. That is where the powerband is.

I've got 31's and 3 inch lift, with 3.55 gears/ 4.0L/ Auto trans on my 1994. Most of my driving is highway and it works pretty good, 4.10's would be great, as during long hills with crusie control on it needs to down shift to maintain 65-70 MPH.

4.10

I have the 5 speed with stock 3.07 gears on 30X9.5s. Jeep still pulls great off the line but, I don't even use 5th until I pass 65... You tend to use first more often which can require some patience and practice. Mileage is not too bad 17-18 and upwards of 20 if I stay off go pedal. I would sugguest a limited slip or locker if you are going to upgrade.