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

[steve68]

Still wondering what gears you bought to do no shimming???

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[XraytecH]

RESPECT for tackling a re-gear yourself.

 

[ShadowsPapa]

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!

When I do differentials. I have a huge pipe wrench I can use, or for AMC differentials, I have a tool that is a long handle with an inert that bolts to the pinion yoke and is open in the middle for a socket.

 

[Escape.idiocracy]

Did you remember to lock tight the ring gear bolts?

 

[Escape.idiocracy]

Still wondering what gears you bought to do no shimming???

Motive gear- at least on JK’s I was able to use the same shin stack on the three I did (pinion shims)

 

[22_Sarge_Sport]

Do you have an update @Bonanza ? How has your experience been?

 

[Bonanza]

Did you remember to lock tight the ring gear bolts?

Edit-- yes I did.

Anyway sorry I missed a few replies. I wasn't getting notifications.

1. I used Dana gears.
2. 4H1 felt before (on 37s, can't even recall driving 4hi stock) like it lugged and didn't have enough power to move. Going uphill, even slightly-- forget about it. Now I see how 4Hi is useful, I can scoot around offroad no problem. I use it a lot now.
3. @ShadowsPapa -- ain't no way a pipe wrench is holding that circular flange with the toque numbers required for that pinion nut. I've never put so much force on a nut in my life, and I can't imagine a pipe wrench with that grip strength. If you can do it, bravo! It was easier on the JK because the flange wasn't a metal circle.

 

[Escape.idiocracy]

I want to say yes, but I didn't. Fuck. Ugh g-D son of a B.

Anyway sorry I missed a few replies. I wasn't getting notifications.

1. I used Dana gears.
2. 4H1 felt before (on 37s, can't even recall driving 4hi stock) like it lugged and didn't have enough power to move. Going uphill, even slightly-- forget about it. Now I see how 4Hi is useful, I can scoot around offroad no problem. I use it a lot now.
3. @ShadowsPapa -- ain't no way a pipe wrench is holding that circular flange with the toque numbers required for that pinion nut. I've never put so much force on a nut in my life, and I can't imagine a pipe wrench with that grip strength. If you can do it, bravo! It was easier on the JK because the flange wasn't a metal circle.

You don’t necessarily have to pull the carrier to pull the ring gear bolts out one by one and apply.

The photos I put up were from my JK…. ??
More beer and BSing was commencing upon reassembly than should have been…. Couple thousand miles in felt/found this.

It’s worth the extra time and effort to apply it…. I know a guy ???

 

[Bonanza]

Do you have an update @Bonanza ? How has your experience been?

I'm almost at the 500 mile marker. So far, so good. MPG back down into the 16s now, which is disappointing. So for all intents and purposes, no MPG improvement. I'm not sure why it's taken a slump, as I'm still easy on it as best I can. I'll update again when I change the oil.

 

[Bonanza]

You don’t necessarily have to pull the carrier to pull the ring gear bolts out one by one and apply.

The photos I put up were from my JK…. ??
More beer and BSing was commencing upon reassembly than should have been…. Couple thousand miles in felt/found this.

It’s worth the extra time and effort to apply it…. I know a guy ???

After your post I texted my F-I-L who was helping me. He did loctite the ring gear bolts while I was looking for the torque wrench. Whew. We both got annoyed at the XX/lbs feet plus 45 degree thing on the ring gear bolts.

 

[Bonanza]

RESPECT for tackling a re-gear yourself.

In all fairness, I had a full-blown mechanic helping me, a lift, and a mechanic's shop worth of tools. This is by no means a DIY. I'm a lawyer by trade and gears is far more challenging that grasping any legal concept I've ever learned. I've "done" (watched) gears on my own cars twice now and still would be clueless doing it alone. My role was easy, taking off the steering, brakes, axles, diff covers, carrier botls, track bars, tires, etc, while my FIL did the bench work and measuring. He did a lot of backlash/preload by feel, which takes a lot of experience.

I'd never, ever do gears alone.

 

[Escape.idiocracy]

After your post I texted my F-I-L who was helping me. He did loctite the ring gear bolts while I was looking for the torque wrench. Whew. We both got annoyed at the XX/lbs feet plus 45 degree thing on the ring gear bolts.

Great news. Beats ordering a new set and going one by one in the Jeep! ???

 

[ShadowsPapa]

Edit-- yes I did.

Anyway sorry I missed a few replies. I wasn't getting notifications.

1. I used Dana gears.
2. 4H1 felt before (on 37s, can't even recall driving 4hi stock) like it lugged and didn't have enough power to move. Going uphill, even slightly-- forget about it. Now I see how 4Hi is useful, I can scoot around offroad no problem. I use it a lot now.
3. @ShadowsPapa -- ain't no way a pipe wrench is holding that circular flange with the toque numbers required for that pinion nut. I've never put so much force on a nut in my life, and I can't imagine a pipe wrench with that grip strength. If you can do it, bravo! It was easier on the JK because the flange wasn't a metal circle.

And thus the special bolt-on tool. It can't slip.

 

[hjdca]

16.7 before, which is about on par, and 17.6 after 1 normal trip. It’s reading 20 mpg now, but that’s due to the break in driving— about 40 mph top speed.

This isn’t a “don’t regear” thread, but I know a LOT of people are on 4.10s and wondering if it’s worth it to jump to 4.88s. On my old Jeep, the jump from 3.21s to 4.56 was night-day. This, from what I can tell, is not night day. More of dusk-night difference.

In a vacuum, 4.88s are spot on and would be my choice if I ordered my Jeep from a menu. But here I am in the real world, with my own shop, wholesale prices, and someone helping me install. I think part of my apprehension is that my Jeep has 16k miles, and I pulled out parts that were pretty much new. I’d be much happier inside if I knew the seals and bearings were worn.

I will update the post after the breakin period and see how I feel.

Do you wish you tried 5:13s ? I am running 5:13s with 37s, but, I have a stick shift JTR. So, I really wanted that low, low 1st gear with the Rubicon transfer case for Rock Crawling. I have been super happy with the 5:13s. On road and off road. MPG has also been great. For me, there is no comparison to the 4:10s.... but, of course, I had to slip the clutch with the 4:10s instead of letting the torque convertor do the work with the 37s.
Note: I live in the mountains, so, I am constantly going up and down hills. If you are on flat land, then, I can see how your experience would be different.

 

[Bonanza]

Do you wish you tried 5:13s ? I am running 5:13s with 37s, but, I have a stick shift JTR. So, I really wanted that low, low 1st gear with the Rubicon transfer case for Rock Crawling. I have been super happy with the 5:13s. On road and off road. MPG has also been great. For me, there is no comparison to the 4:10s.... but, of course, I had to slip the clutch with the 4:10s instead of letting the torque convertor do the work with the 37s.
Note: I live in the mountains, so, I am constantly going up and down hills. If you are on flat land, then, I can see how your experience would be different.

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.

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