Opinions on 4.10 vs 4.56 vs 4.88 gear ratio for 31" tires

[jmask]

I know there's a number of threads on this already so I am sorry if I'm repeating some already-discussed info.

My jeep is a 2000 4L 5spd manual with what I'm pretty sure is a 3.73 gear ratio (last owner took off the metal tags on the axle for some reason). I'm currently running 31" tires on stock suspension, and I plan to add a 2.5" suspension lift in the near future (keeping same 31" tire size).

I got in touch with a shop about installing some lockers and running a re-gear to 4.10 while they're in there, as I had read a few threads recommending a 4.10 ratio for a setup like mine. The guy I chatted with highly recommended I go to at least 4.56 or even up to 4.88, saying 4.10 wouldn't be adequate or worth the regear coming from 3.73.

I'm curious on what people's opinions on this recommendation are? 4.56 seems doable but 4.88 seems way high considering this is still my daily driver until I get a more practical rig. That being said I'm a relatively new jeep owner and don't know nearly as much as a lot of you folks on here.

Thanks in advance

 

[Jerry Bransford]

Welcome to the forum jmask! Understand that regearing axles costs somewhere between $1300 and $1600 or even higher if the shop is trying to gouge you.

Two questions for you... 1) what size tires MIGHT you ever get up to? 33"? Maybe even 35"? Or are you absolutely going to draw a line in the sand at 31" tires?

2) And the more important question, what rear axle is in your Jeep? The standard factory axle is a Dana 35 which is not strong enough in stock form for a locker. Or the optional extra-cost Dana 44 rear axle? The Dana 44 is definitely strong enough for a locker.

Take a look at your rear axle to see what shape its differential cover is. And take a look at the plug in the lubrican fill hole in the center of the cover. The Dana 35 has a snap-in black plastic plug, the stronger/more desirable Dana 44 has a threaded steel plug in the fill hole.

 

[jmask]

Ah yes forgot to mention that I have a Dana 44 rear. I plan to put an ARB air locker on both axles.

In terms of tires. I'm a bit undecided.. As a fairly new Jeep owner I'd like to say I'll stick with 31", but I have a feeling a lot of folks with bigger tires start out saying the same thing. I'm somewhat inclined to go with the 4.56 ratio just in case I decide on moving up in the future, but 4.88 still seems crazy tall

 

[Jerry Bransford]

Ah yes forgot to mention that I have a Dana 44 rear. I plan to put an ARB air locker on both axles.

In terms of tires. I'm a bit undecided.. As a fairly new Jeep owner I'd like to say I'll stick with 31", but I have a feeling a lot of folks with bigger tires start out saying the same thing. I'm somewhat inclined to go with the 4.56 ratio just in case I decide on moving up in the future, but 4.88 still seems crazy tall

Don't let 4.88 make you think it's crazy tall when it is installed for 35" tires.

Don't forget that the intent of the ratio change is only to restore the rpms back up to where they were with the smaller tires... or just tad higher due to the larger tires requiring more power. You wouldn't notice anything different about your engine rpms by regearing to 4.56 for 33's or 4.88 for 35's.

If you were to install 35" tires on your Jeep tomorrow and were to drive 65 mph on the highway, your rpms would be several hundred lower than what they were before the 35's were installed (for example). And the engine would be lugging, you wouldn't be able to accelerate, and you'd struggle going up hills. Regearing with 4.88 (4.56 for 33's, etc.) would just restore the rpms back up to where they need to be for the tire size you're running.

In other words, you won't have crazy high rpms on the highway regearing to 4.56 for 33's or 4.88 for 35's... they'd be very close to what you have now with 31's. And those ratios are recommended based on their highway rpms, not offroad rpms where the exact ratio is not nearly the issue it is when on the highway.

 

[jmask]

Right, but (for now) I plan to keep my 31"s. I guess my questions are, would things be miserable with a 4.56 on 31" tires? Should I stick to 4.10? Is it even worth the cost of regearing from 3.73 to 4.10 on 31"?

 

[Jerry Bransford]

Right, but (for now) I plan to keep my 31"s. I guess my questions are, would things be miserable with a 4.56 on 31" tires? Should I stick to 4.10? Is it even worth the cost of regearing from 3.73 to 4.10 on 31"?

It's not worth the cost to regear from 3.73 to 4.10 just for 31's. Only if your axle ratio was 3.07 would I consider it. If you have 3.73 as you believe you do I'd stay with that until getting to 33's.

 

[never monday]

Right, but (for now) I plan to keep my 31"s. I guess my questions are, would things be miserable with a 4.56 on 31" tires? Should I stick to 4.10? Is it even worth the cost of regearing from 3.73 to 4.10 on 31"?

Play with the calculator on GrimJeeper

 

[Jamesval035]

I’d say if your planning on getting in there for ARB lockers and set with that decision, then maybe go with the 4.56. Your tires will eventually wear, and you’ll want to jump to 32/33” tires. We all do, It’s inevitable.