Re-gearing: Are 4.10's Too Big?

[sixty7ss]

My front gears are shot, so I'm upgrading my gears. I was originally going to go with 3.73 gears, but neither Motive or G2 make 3.73 gears for the Chrysler 8.25.

That being said, am I going to hate 4.10's on the highway? I've always understood those to be great for climbing, but terrible for gas mileage on highway. What are your thoughts?

Because I know you're going to ask, I'm going with Motive or G2 because I can get them at a discount and I'm poor.

 

[Bjorn86]

What tire size will you be running?

 

[sixty7ss]

31's. Potentially 32's in the future.

 

[sixty7ss]

https://www.dropbox.com/s/k2rccbnndjlknrs/gear_ratio_chart.JPG

According to that chart, I should be okay, but I'm seriously concerned with gas mileage. I know that 3.55's are too small for what I'm doing, especially if I plan on doing any wheelin', which I do.

It looks like 3:73 gears would be best all around, but I can't find them for the Chrysler 8.25, except from Yukon, who are awfully proud of them.

 

[PacificEd]

I like my 4.10 gears when I ran 32's and now 33's. On long grades 4.56's might be nicer but overall I'm happy with the 4.10 ratio.

 

[cheapcherokee93]

have you thought about 4.56? i have 4.10s on 29s and i think its great. the higher rpms on the highway havent really affected mileage for me. deep gearing is awesome, I'm gonna wish i had 4.56s when i slap on some 31s

 

[Johnnie Walker]

I have 4.10s with 31's no plans of larger, not until a V8 swap but at that point I may not need to re-gear again. It's nice. My mileage took a hit with 31's and stock 3.55s. If you can find a set of axles from a 4cyl that is usually the cheapest way to go.

 

[sixty7ss]

Also, I have an old Chevy truck running 4.11 gears. That thing tops out at about 65 mph. It's got torque for days, but no top speed. I really don't want that in my daily driver. Thoughts?

 

[XJLI]

5spd or auto?

 

[NorCalChris]

Also, I have an old Chevy truck running 4.11 gears. That thing tops out at about 65 mph. It's got torque for days, but no top speed. I really don't want that in my daily driver. Thoughts?

A few things here. First, this is two seperate vehicles. Second, two different transmissions. Third, probably two different size tires. Fourth, your old chevy truck engine is probably stock and carbed. If its a small block it doesnt have very much if any more power then a stock 4.0.

With 5.13s and 35s in a stock 4.0 with an auto you can do 70 and still get 20 mpgs. Some have even seen more. This is how i rate Xj gearing.

Tires:
30's and down- 3.55-3.73
31's- 4.10
32's-4.56
33's-4.88
35's and bigger. 4.88s or build a different axle that can gear deeper or get tcase gears.

Yes , auto's and manuals are geared differently, but with these tire/gear combos you wont be disappointed. I know guys running 35's and 4.56's. They are happy, I know guys running 35s and 5.13's. They are happy.

 

[Marcelo73]

I have 3.07 (5sp manual) with 30" tires. At 70mph is about 2000rpm. In the mud with 4x4lo still lot of torque to attack sand and mud. I'll be regearing to 4.10 and maybe swap to a 32-33" tires. However I have the impression the 4.0 has constant mileage: too low

 

[sixty7ss]

A few things here. First, this is two seperate vehicles. Second, two different transmissions. Third, probably two different size tires. Fourth, your old chevy truck engine is probably stock and carbed. If its a small block it doesnt have very much if any more power then a stock 4.0.

With 5.13s and 35s in a stock 4.0 with an auto you can do 70 and still get 20 mpgs. Some have even seen more. This is how i rate Xj gearing.

Tires:
30's and down- 3.55-3.73
31's- 4.10
32's-4.56
33's-4.88
35's and bigger. 4.88s or build a different axle that can gear deeper or get tcase gears.

Yes , auto's and manuals are geared differently, but with these tire/gear combos you wont be disappointed. I know guys running 35's and 4.56's. They are happy, I know guys running 35s and 5.13's. They are happy.

Awesome. That's what I was looking for. I'm doing a bunch of other air/fuel/exhaust mods to get better power/mileage, too. Keeping fingers crossed.

 

[Ogrebonz]

I had to make the same decision last spring and went with 4.56. I'm running 32's and don't plan on going any bigger. It took a lot of research, reading posts and head scratching, but I've never looked back. IMHO 4.56 is perfect for 32" tires. Fuel economy? Did you post to the right website? We all drive XJ's here.

Seriously though, my MPG got about .5 better after the gear change, and now I have a Detroit Locker in the back and a Truetrac in the front. I think the 4.0 and the auto trans are both a lot happier now.

Oh, and you won't top out at 80... ask me how I know.

 

[blubullett]

I have 32's with 4.10's and they are pretty nice. I get better mileage wth the 4.10's and 32's then I did with 3.55's and 30's and much better pick up. I figured they were a good comprimise between fuel milage and wheeling ability. If you are planning on going ANY bigger though I would get 4.56's.

 

[Planetcat]

31's with 4.10's is a good setup. You will have zippy accelleration around town and not tach terribly high on the freeway, unless you want to drive it over 80 mph for long periods of time.

 

[ingenio]

My front gears are shot, so I'm upgrading my gears. I was originally going to go with 3.73 gears, but neither Motive or G2 make 3.73 gears for the Chrysler 8.25.

That being said, am I going to hate 4.10's on the highway? I've always understood those to be great for climbing, but terrible for gas mileage on highway. What are your thoughts?

Because I know you're going to ask, I'm going with Motive or G2 because I can get them at a discount and I'm poor.

you will enjoy 4.10s w 31s..
if funds are scarce, look for a d30 from a 4 cyl in the junkyard....you will find it for less than the regear labor costs...
for the rear get a explorer 8.8 with 4.10...those are cheap (150/200)..plus the xj kit...(another 200),,,,total 400 or less...pretty much the parts cost for the 4.10 gear +master kit install...
and you can sell your d30 an c8.25 for 200 the combo..

 

[Talyn]

I have 4.11s w/ some 75% worn 30.5" tires (245/75R16). Doing 80mph on the highway I am pulling 3000 rpm. AW4 auto. Don't know about mileage yet.

 

[sixty7ss]

Turns out that my gears are just fine. I popped open the pumpkin last night and had my regular mechanic look 'em. He said the fluid was black, but no metal shavings. Bearings all looked good.

We did find, however, that my transmission mount is broken. That could easily account for what I assumed was grinding gears.

Good news, I guess.

 

[themauler]

I have 4.11s w/ some 75% worn 30.5" tires (245/75R16). Doing 80mph on the highway I am pulling 3000 rpm. AW4 auto. Don't know about mileage yet.

4.56 gears on 30inch tires. On the highway my I6 pulls 2750-3000rpm through my aw4 to maintain 65-75mph. I researched the 4.0 doesn't mind that work. If anything I noticed an increase in mileage pushing it over 18mpg. Really zippy around town.

 

[djlarroc]

i'm considering the same.. 4:10 vs 4:56. currently on 245/75, later planning on going to 265/75. my xj (auto) feels strong now on 3:55s, but i know my mileage is going to suffer. just put the lift/tires on a week ago, so haven't had a chance to check mpg.