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

[Wheelin98TJ]

Nah. I like the RPMS on the highway with 4.88s. 2k at 70. I live in the flatter desert areas in the SW. I also have the regular X-fer case. 5.13 would be too tall I think, I don't like the idea of skipping gears because they effectively lose usefulness if the ratio is too tall. This rig is also my daily driver so I wanted it to simply be close to stock. I believe my MPG issue is that my tires do best at 35 psi, and its been 115+ daily on the regular.

4.88 is "taller" than 5.13.

You can cruise in 8th at 2k RPMs with 37s? Mine would never cruise in 8th at 2k RPMs with 35s. Though I did get a new transmission recently and I haven't had it on the highway since the new transmission.

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[Bonanza]

4.88 is "taller" than 5.13.

You can cruise in 8th at 2k RPMs with 37s? Mine would never cruise in 8th at 2k RPMs with 35s. Though I did get a new transmission recently and I haven't had it on the highway since the new transmission.

At 70, yes. 2000 or 2100.

 

[OngsterA]

Following this thread, thanks to OP for sharing your install and feedbacks, kudos! For anybody here, I have to do stepwise upgrades to know and feel differences. Main question is for now, with my OEM 4.10 and 35s, since I do wheel and crawl often here in CA, when I take the jump to 37s without re-gearing, will the climbs be noticeably harder in both 4HI and 4LO? Can I still do most trails without hurting the 3.6 or ZF trans? How about on-road at 65-75mph? Noted here mpgs are almost identical.

 

[Vtur]

If anyone else has done there own gears, I really want to know how you held the flange while giving it 360 lbs ft of torque. I didn’t see that in any install video or write up and is easily the hardest part. We borrowed an impact gun that resembled a Gatling gun and weighed about 50 pounds, but it still spun the flange. Lost about a half day trying to figure that out!

I used something like this but 3ft long to holds both, the flange and carrier to loosen/torque the ring gear.

 

[Bonanza]

Following this thread, thanks to OP for sharing your install and feedbacks, kudos! For anybody here, I have to do stepwise upgrades to know and feel differences. Main question is for now, with my OEM 4.10 and 35s, since I do wheel and crawl often here in CA, when I take the jump to 37s without re-gearing, will the climbs be noticeably harder in both 4HI and 4LO? Can I still do most trails without hurting the 3.6 or ZF trans? How about on-road at 65-75mph? Noted here mpgs are almost identical.

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.

 

[Bonanza]

I used something like this but 3ft long to holds both, the flange and carrier to loosen/torque the ring gear.

Had it, tried it, didn't work. The chain slips right off the flange. The torque needed to get the crush sleeve to go is astronomical.

 

[OngsterA]

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.

That's great to hear, 10K miles AND wheeled hard! I'm fine on 35s on the steeps, kept hearing 4.10s are borderline when upping to 37s. I use 4LO anyway for these situations, easier on the transfer case, tranny, motor. People say "I'm on 4HI never touched 4LO" but our Jeeps work harder that way, use 4LO to its benefit. Thanks for your inputs!

 

[Bonanza]

That's great to hear, 10K miles AND wheeled hard! I'm fine on 35s on the steeps, kept hearing 4.10s are borderline when upping to 37s. I use 4LO anyway for these situations, easier on the transfer case, tranny, motor. People say "I'm on 4HI never touched 4LO" but our Jeeps work harder that way, use 4LO to its benefit. Thanks for your inputs!

I never had a problem with 4Lo. I'd want a slower 1st gear crawl speed sometimes, and found I did a lot of 2-foot wheeling, but overall no problem. All big bear trails, Ocotillo. I've been around the hammers a ton but haven't wheeled clawhammer or Turkey claw yet. Those are demanding trails.

 

[Vtur]

Had it, tried it, didn't work. The chain slips right off the flange. The torque needed to get the crush sleeve to go is astronomical.

It worked for me. I lean it against the floor since i did the install using jack stands.

This method will only work with the use of a breaker bar, won't work using impact gun.

 

[Bonanza]

Update as I'm nearing the 500 mile break in. MPG down to 15.6. I'm back and forth opinion wise, but I'm going to have to confirm that a jump from 4.10 to 4.88 is not a $2-4,000 difference. Still fairly "meh" on the whole thing. But, I'll change the oil (going up to 75-140) and see what happens. It's also 116 out regularly, so who knows. I'm also interested to see what happens when I can drive it without feeling like I need to baby it.

Stay tuned...

 

[Orange01z28]

Update as I'm nearing the 500 mile break in. MPG down to 15.6. I'm back and forth opinion wise, but I'm going to have to confirm that a jump from 4.10 to 4.88 is not a $2-4,000 difference. Still fairly "meh" on the whole thing. But, I'll change the oil (going up to 75-140) and see what happens. It's also 116 out regularly, so who knows. I'm also interested to see what happens when I can drive it without feeling like I need to baby it.

Stay tuned...

I am installing 5.13s on Monday (well, getting them installed)

When i first got my 37s I was really close to not doing the install and selling the kit due to the cost because of these same reasons. However, I recently went wheeling and the Jeep struggled on a couple climbs that never even bothered it on 35s and 3.73s. It was not happy with 37s and 3.73s

If I didn't offroad it would be a different story

 

[Tim]

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.

 

[kevman65]

Update as I'm nearing the 500 mile break in. MPG down to 15.6. I'm back and forth opinion wise, but I'm going to have to confirm that a jump from 4.10 to 4.88 is not a $2-4,000 difference. Still fairly "meh" on the whole thing. But, I'll change the oil (going up to 75-140) and see what happens. It's also 116 out regularly, so who knows. I'm also interested to see what happens when I can drive it without feeling like I need to baby it.

Stay tuned...

Give it awhile. The computer is still relearning driving habits, shift points and such.

 

[Escape.idiocracy]

Update as I'm nearing the 500 mile break in. MPG down to 15.6. I'm back and forth opinion wise, but I'm going to have to confirm that a jump from 4.10 to 4.88 is not a $2-4,000 difference. Still fairly "meh" on the whole thing. But, I'll change the oil (going up to 75-140) and see what happens. It's also 116 out regularly, so who knows. I'm also interested to see what happens when I can drive it without feeling like I need to baby it.

Stay tuned...

Something you may want to put on your radar. I’m pretty sure all GL6 rated gear oil is natural and not synthetic. Additional note- Currie enterprise will not warranty their gear sets if synthetic gear oil is used.

I picked this information up a few years ago in one of their booths. Their high pinion 9’s apparently amplify the heat issue- but theory in my opinion would apply across the board.

Stay with me a bit…. I understand that under most applications we have all pushed to a synthetic is better mind set. This isn’t the case with differential gears. Non-synthetic gear oil helps with heat soak.

It’s counter intuitive, I get it…. But it’s worked for our jeeps with 4.56+ gear sets as well as our UTV’s for racing.

 

[Bonanza]

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.

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.

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