We installed 4.88s from a 4.10. (37” tire). Review, tips, and notes inside!

[BumbleBee]

I have done many regears over the years, and have accumulated all the right tools including the bearing set pinion depth tool (save a ton of time). Personally I have had a couple of sets that were acceptable with stock shims, but not many. I will also say this, unless you are extremely tight, you won't have problems if they are a little off. These vehicles don't have enough HP and towing capacity to really strain the system (some will disagree). Crawling does put some strain (but not heat) on the gears, but if you pull a maneuver that could break a gear, you will break anyways in many situations.

Last advice,,, always pick one gear set lower than you think you want. IMHO

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[Bonanza]

I have done many regears over the years, and have accumulated all the right tools including the bearing set pinion depth tool (save a ton of time). Personally I have had a couple of sets that were acceptable with stock shims, but not many. I will also say this, unless you are extremely tight, you won't have problems if they are a little off. These vehicles don't have enough HP and towing capacity to really strain the system (some will disagree). Crawling does put some strain (but not heat) on the gears, but if you pull a maneuver that could break a gear, you will break anyways in many situations.

Last advice,,, always pick one gear set lower than you think you want. IMHO

I just googled that. If I knew it existed I would've bought it. [Sigh]

 

[BumbleBee]

I have used it many times. Works great after you understand it. BUT,,, some cheaper gear sets don't have the mating measurements on them. In those cases, the tool is worthless. But you shouldn't be buying the cheap stuff anyway!

 

[Tim]

I had a 4 door JK on 35s with the 4.10. 100% fine. (Granted, that was a 6 speed) If you're on 35s I really would not advise regearing unless you just want to be thousands of dollars poorer. To each their own, but I'm still not over the moon. I also would never advise aftermarket exhaust because I find it to be excruciating to hear anything less than a V8, but again-- to each their own!

I regeared my old '13 JK door 2 door on 35s when it came with a 3.21 ratio. I bumped it up to 4.56 and that was, without a doubt, a night/day experience. This... meh. Mildly better to be sure, but so far the biggest bang for my buck was getting a usable 4HI experience again. I find myself using it a lot now.

I have no desire to regear for the 35's. That's why I bought a truck that came with stock 4.10s. I was merely speculating that based on my time with the 35's I can't imagine how 37's would be an acceptable driving experience, to me, with stock gears. I guess you could get by with the 4.10s but even you said 4hi was useless. 8th gear also becomes pretty much useless. To each their own...

 

[hjdca]

I have no desire to regear for the 35's. That's why I bought a truck that came with stock 4.10s. I was merely speculating that based on my time with the 35's I can't imagine how 37's would be an acceptable driving experience, to me, with stock gears. I guess you could get by with the 4.10s but even you said 4hi was useless. 8th gear also becomes pretty much useless. To each their own...

Good point. It is not all about highway gearing.... Shifting to a lower gear set that gives you your last gear for the hwy, allows you to use all your gears for superior acceleration, better 4WH, better 4WL for crawling. So, it is a game changer - stop light to stop light, If you hwy drive, and if you do a bunch of 4wheeling.... The whole experience is greatly enhanced.

 

[Mjolnir]

I dont think it was answered yet... @Bonanza did you reprogram your computer for the new gearing size? If not that would have an effect on your MPG's and shift points. It seems the shift points are fine currently from what you have been saying but wanted to double check is all

 

[Bonanza]

I dont think it was answered yet... @Bonanza did you reprogram your computer for the new gearing size? If not that would have an effect on your MPG's and shift points. It seems the shift points are fine currently from what you have been saying but wanted to double check is all

The computer would go into limp mode if you don't. So yes, I did.

 

[Mjolnir]

The computer would go into limp mode if you don't. So yes, I did.

Cool just making sure since I didnt see it posted. Didn't realize it would go into limp mode, I've never regeared and not reprogramed the same day lol.

Thanks for the response

 

[Bonanza]

Updated the main post with my findings on the oil change. Noticeable amount of metallic shavings in the rear, but no chunks. We'll see how it goes.

 

[Geoarch]

4.10 and 37s was perfectly, absolutely fine in my opinion. I did it that way for 10k miles and would have stayed that way if I had to pay retail prices and also pay for an install. The gearing is more quality of life. I wheeled hard in 4.10s and 37s. 4HI kind of bogged down and I never used it much. Now, it's much better.

So I’m assuming that 35s and 4.10 will be fine in low range. Actually stock Falkens are 32.8 and the Kanatis I’m putting on are 34.5.

 

[Bonanza]

So I’m assuming that 35s and 4.10 will be fine in low range. Actually stock Falkens are 32.8 and the Kanatis I’m putting on are 34.5.

You'll be more than fine. Especially with the 8 speed. On an auto JK, you might be wanting more, but these new transmissions are really well done.

 

[Geoarch]

You'll be more than fine. Especially with the 8 speed. On an auto JK, you might be wanting more, but these new transmissions are really well done.

I have a MT, so we'll see. There are others here with 35s and an MT, NachoRuby I think, and he says its fine on and off road. I believe 1st and maybe 2nd on the MT is lower than the auto.

 

[Hank_]

I also would never advise aftermarket exhaust because I find it to be excruciating to hear anything less than a V8, but again-- to each their own!

This! It must be the old man in me but unless it is a healthy V8 I do not want to hear any exhaust sounds, especially from Harley's with loud pipes. I never understood it. But like you said. To each his own.

Hank

 

[mrmo]

Not gonna lie, this thread is not what I expected. I’m on 35’s with 4.10s and I’m constantly between 7th and 8th on the highway. I know that’s what you mean by quality of life but that would be worth it to me on it’s own. I have an exhaust on mine so the back and forth between 7th and 8th is very noticeable and quite annoying.

4.10 w 35's should be right in the sweet spot...should be able to hold 8th at 2000rpm w 75-77mph

 

[Tommyd]

I wouldn’t have done anything different. 4:88s all day long. My JT setup loves them.

18 mpgs All day long as well.

With what tire size? Just curious

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