AX-15 setup using 31x10.5 tires & 3.73 gears vs 33x10.5 tires and 4.10 gears for a DD

Mirage mobile · Oct 1, 2013

AX-15 setup using 31x10.5 tires & 3.73 gears vs 33x10.5 tires and 4.10 gears for a DD

Anyone have an opinion on the matter:

AX-15 setup using 31x10.5 tires & 3.73 gears vs 33x10.5 tires and 4.10 gears for a DD (80% onroad).

According to this gear calculator, both setups will have slower crawl speeds and lower engine rpms at 65mph when compared to the standard forum recommendations of an AW4 setup using 31s and 4.10s vs 33s and 4.56.

After some calculations and talking to a few forums members, I believe 4.10s and 31s with the AX-15 will be too low of a gearing for a DD.

I'm sitting with 3.07s in a dana 30 HP and dana 35 LSD on stock tires. What would be the best way to go about axle upgrades (never going above 33s, maybe rear LSD and eaton e-locker in front).

1. Hardest part would be finding 3.73s in a HP Dana 30 and Chrysler 8.25, right?
2. If sticking with 3.73s and not finding axles, then I must buy gears for the HP Dana 30, buy a chrysler 8.25 and regear it to?
3. Could jump to 33x10.5 tires and 4.10s (more common gearing to find axles for, correct?).

Can anyone weight in on the handling differences between 31x10.5 and 33x10.5 tires. I could also go to 16" wheels, haven't decided on a tire yet.

Devilfrog · Oct 1, 2013

Re: AX-15 setup using 31x10.5 tires & 3.73 gears vs 33x10.5 tires and 4.10 gears for

3.73 was only a standard ratio in the ZJ and TJ's both a LP D30, and both having D35 or D44 as the only available axle options (ZJ D44a though).

So if you go with 3.73 add the cost of regearing both axles.

If you plan to eventually swap to 33 skinny's run the 4.10's and find a set of stock 4cyl axles. I don't think 4.10s are too much for a DD on 31's they are in the good range for a trail/DD oriented rig. 3.73s would be better for one that sees a lot of highway travel, and the 4.10's would actually be better for a city stop and go rig. You wanna cruise between 1500 to 2000rpm ... at say 55mph both ratios fall into that category.

Just my thoughts on the subject

themauler · Oct 1, 2013

Re: AX-15 setup using 31x10.5 tires & 3.73 gears vs 33x10.5 tires and 4.10 gears for

I DD a xj on 33x10.50s with an ax15 and 4.56 gears spartan locked front and rear. One thing is the backlash from the auto locker in the rear during a hard left or right turn on pavement will travel all the way up to the ax15 if coasting around the corner with the clutch pedal down. Other than that the set up works.

4.10s would probably be perfect for economy but I get 16-20mpg average with the 4.56s. I have plenty of 5th gear torque (2900ish rpm @ 75mph) to maintain highway speeds up large grades in the appalachian mountains and the first gear is nice and deep to get moving forward when rolling back on a hill. Makes the 4.0 feel like it has tons of power.

On level ground I can just let the clutch out in first gear and it won't stall. On a final note the 33x10.50s BFG A/Ts don't measure 33" more like 32" or less.

FloydXJ · Oct 1, 2013

Re: AX-15 setup using 31x10.5 tires & 3.73 gears vs 33x10.5 tires and 4.10 gears for

Whether an axle upgrade is needed depends on your wheeling. A D35, while extremely unpopular amongst these forums, is not a time bomb. It can handle those 33s with an LSD if you are conservative (for reals...it can...really conservative party1

. That being said, if you are regearing anyway, I would still recommend moving to a 29 spline 8.25.

There is never a definitive way to go - it comes down to preference. The MPG changes very little overall. The bog of high gears and the high RPM of low gears kind of cancel eachother out when all is said and done. If you are doing primarily highway, maybe 3.73, more city, maybe 4.10.

sidriptide · Oct 1, 2013

Re: AX-15 setup using 31x10.5 tires & 3.73 gears vs 33x10.5 tires and 4.10 gears for

i ran my 5 spd 90 XJ on 31s with a set of swapped in stock D30/8.25 with 3.55s. it was a great combination for DD. the next step was 33x10.50s and 4.56s with a D44 in the rear.
another great set-up. made the 6000 mile round trip to Moab with an average 18 mpg and lots of good 5th gear torque.
my biggest suggestion, DO NOT be afraid of higher RPM on the highway. the easier workload on the engine will help you maintain good fuel economy if you dont drive like a race car all the time.
always select your gears for what the future may hold. 3.73s and 4.10s are ok for smaller tires and occasional wheeling, but before you spend the money take a realistic look at where you want the rig to take you.
you never want to pay full price to regear your rig twice.

gradon · Oct 2, 2013

AX-15 setup using 31x10.5 tires & 3.73 gears vs 33x10.5 tires and 4.10 gears ...

I have both the 3.73 and 4.10 used gear sets for the Chryco 8.25" if you go that route and are interested.

souske · Oct 2, 2013

Re: AX-15 setup using 31x10.5 tires & 3.73 gears vs 33x10.5 tires and 4.10 gears for

Go 4.10s and then try both sizes if you can.
Wheeled 3.07s and 33s for a while, finally stepped up to 4.10s after I found an 8.8 and non disco 30 in a c4c xj
Just stepped up to 5.13s with 33s. It crawled awesome, but spun a little too fast for my liking for extended trips
Just stepped up to 35s and it seems to.be.a.happy medium

These mt rigs need way more.gear than they came.with.
4.10 on the cheap, either tire size
4.56 &33" if you cant find a deal

grainofsalt · Oct 2, 2013

Re: AX-15 setup using 31x10.5 tires & 3.73 gears vs 33x10.5 tires and 4.10 gears for

Mirage mobile said:
Anyone have an opinion on the matter:

AX-15 setup using 31x10.5 tires & 3.73 gears vs 33x10.5 tires and 4.10 gears for a DD (80% onroad).

According to this gear calculator, both setups will have slower crawl speeds and lower engine rpms at 65mph when compared to the standard forum recommendations of an AW4 setup using 31s and 4.10s vs 33s and 4.56.

After some calculations and talking to a few forums members, I believe 4.10s and 31s with the AX-15 will be too low of a gearing for a DD.

I'm sitting with 3.07s in a dana 30 HP and dana 35 LSD on stock tires. What would be the best way to go about axle upgrades (never going above 33s, maybe rear LSD and eaton e-locker in front).

1. Hardest part would be finding 3.73s in a HP Dana 30 and Chrysler 8.25, right?
2. If sticking with 3.73s and not finding axles, then I must buy gears for the HP Dana 30, buy a chrysler 8.25 and regear it to?
3. Could jump to 33x10.5 tires and 4.10s (more common gearing to find axles for, correct?).

Can anyone weight in on the handling differences between 31x10.5 and 33x10.5 tires. I could also go to 16" wheels, haven't decided on a tire yet.

I had some BFG A/T's in 30/9.5, They felt about the same power-wise as the 235/70r15's that were on before. You could feel the taller size a little starting off from a stop. In 4 low they were great for what trails I did.

Just my .02

AX-15 setup using 31x10.5 tires & 3.73 gears vs 33x10.5 tires and 4.10 gears for a DD

Mirage mobile

NAXJA Forum User

Devilfrog

NAXJA Forum User

themauler

NAXJA Forum User

FloydXJ

NAXJA Forum User

sidriptide

nobody of any consequence

gradon

NAXJA Forum User

souske

NAXJA Forum User

grainofsalt

NAXJA Forum User

Similar threads