Ok, I currently have 34x10.50 swamper LTBs on the old XJ running 4.10 gears. Not much use for the swampers since we moved to KC. I can get a smoking deal on some 31x10.50 a/t which would be a lot more street friendly. Is 4.10 to much gear for the 31s on the Interstate? 65-75 mph? 4.0 H.O. with aw4 auto.

 

No that would be fine.

With any re-gear to those lower ratios you're going to eat more gas because of the higher RPMs at higher speeds, but your transmission will take it without really bugging you. Especially since you have an automatic, the torque converter is going to do most of the work to get you to speed anyway.

Since you're getting smaller tires though, you'll probably save gas in this situation. 4.10s aren't really highway gears like 3.55s are, but they're not as gas-guzzling as 4.56s can be at those speeds.

 

4.10's and 31's will keep you close to the stock powerband

 

Hell I'll be ridding on 4.88 with 32" tires soon

 

you will be fine

you jeep will really get up and move now

my 91 was a HO and it had 31s with 3.55 gears and it was fast (considering what it was)

cant imagine what 4.10 would do

throw a 50 dollars trans cooler on it and you will be fine

that aw4 will take more abuse than people realize....especially when you have a aftermarket cooler on it

 

I had the opportunity to test out my buddy's Jeep to get it to him at work and he just installed 4.10s and runs 33s. In case you are interested, along with OP, here is some information about my experience:

Now I use 3.55s and 33s and my Jeep really gets up and goes. My buddy's Jeep feels like with 4.10s it gets up and goes from 0-35 faster, but it's a dog at higher speeds. Mine has little or no resistance from 20-60 and it's a dog after that.

Notably, if I were to bring both Jeeps to a private road and floor it against his up to a reasonable speed (0-40ish), mine still seems to pull away from a complete stop with 3.55s. I must just have a stronger motor than he does, or transmission. On the other hand he has a 98 and I have a 99, so there was very little motor difference between both years apart from the improved intake.

Overall, I would say 4.10s are good for the guy looking to improve their gas mileage around town. If you do a lot of highway driving, I would recommend sticking with 3.55s.

I have actually considered moving to 4.10s. But only for a good price. Not dying without them

 

In an auto it'll be ok. In a manual it will suck.

I had 31s for awhile til i got my 33s. First geqr was useless, 5th gear at highway speeds was spinning the motor stupid fast.

Manuals and autos are geared differently from the factory, typically 3.07 for manual and 3.55 for auto, with very few options.

 

You seem to contradict yourself there. Ideally you want to keep the final ratio as close to the factory ratio as possible for best combination of MPG and giddyup. That was implied here: I have 33" tires and 3.55 gears and my highway MPG is worse now than it was with 31" tires and 3.55 gears. City is worse too.

 

Yeah I can see why that may seem contradicting.

Basically it felt like I had less resistance with his 4.10s, giving the illusion that it may be faster. On the other hand, he may not have as strong as a motor.

My Jeep didn't seem like it accelerated that quickly, but for some reason I still take him off the line.

Hopefully this clarifies.

 

Driver error? Maybe it could be a lot of things. I just read this post bored at work and I'm also interested in re-gearing my 99 sport 2wd with 31" BFG km2 m/t. The reason is my gas mileage is terrible I get about 11.2 to a gallon. Ill also be doing other things such as the 784 neon injectors and that good stuff. But back to the gears, I do most of my driving around town and a little bit of wheeling. So it would be advised to put 4.10s in my 8.25 29 spine line? I don't know my stock gear ratio but it's obviously going to be a shorter gear like a 3.55 maybe? Advice? Comments? Thanks!

 

^ oh and it's an automatic