456 vs 488 Questions

[grimmjeeper]

@nvgearhead, not to give you something else to consider, but here's something else to consider: a numerically higher gear ratio means more teeth. Those teeth are going to be thinner to be able to fit. Thinner typically means weaker.

Not that anyone ever has diff issues, but my rig is currently in the shop dealing with diff issues.

Sure, tooth count changes. But that doesn't always mean more teeth. The number of teeth on the ring stays within a small range. As the pinion diameter goes down, you get fewer teeth. But without getting significantly bigger or smaller teeth.

For example, a 4.10 gear set (41/10) and a 3.73 (41/11) have the same number of teeth on the ring gear. They're roughly the same size because the ring gear doesn't change diameter. The 4.10 pinion has 10 teeth. The 3.73 pinion has 11. But since the 3.73 pinion head is roughly 10% bigger in diameter, the pinion teeth are roughly the same size.

Same thing applies between the 4.30 gears (43/10) I took out of my dana 80 in favor of the 5.38s (43/8).

But even when you factor in more teeth, you also start to see more teeth in contact at any given point in time. And that makes up for the teeth being weaker.

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[grimmjeeper]

Doing the math, you have a very small variation in tooth counts.

3.45 = 38/11
3.73 = 41/11
4.10 = 41/10
4.56 = 41/9
4.88 = 39/8
5.13 = 41/8
5.38 = 43/8

Personally, if I was specifying the gears I would have done 3.42s (41/12) instead of 3.45s.

 

[Ratbert]

Doing the math, you have a very small variation in tooth counts.

3.45 = 38/11
3.73 = 41/11
4.10 = 41/10
4.56 = 41/9
4.88 = 39/8
5.13 = 41/8
5.38 = 43/8

Personally, if I was specifying the gears I would have done 3.42s (41/12) instead of 3.45s.

I guess that means my 4.63 gears are 37/8, implying fewer overall teeth than the other gears listed.

 

[grimmjeeper]

I guess that means my 4.63 gears are 37/8, implying fewer overall teeth than the other gears listed.

Which probably means those teeth are bigger.

 

[Ratbert]

Which probably means those teeth are bigger.

Yeah, and I've had them replaced twice so far on my '22.

 

[grimmjeeper]

Yeah, and I've had them replaced twice so far on my '22.

Yeah, they weren't spec from Dana Spicer. I suspect nitro did that on their own. Makes me suspicious about how good they really are. Or maybe you just got back to back bad gears. Or something else. Who knows for sure.

 

[JamesWyatt]

4:88's, V6, Auto, 35's, at 60mph = 2000rpm
70mph = 2300rpm
80mph = 2500rpm
My mileage varies between 16-18 mpg for normal street/highway driving.
Go for it, you won't be disappointed.

In case someone wants to see a similar setup at 75mph and 8th gear (4:88/Auto/Factory 35 KO2s) :

75mph + mild downshift to 7th:

I ordered 4:88s on my 24 TJR-X and LOVE THEM, it really wakes up the 3.6 and I get 16.x on the highway, good enough for me...

Couldn't agree more. And let's face it, the 3.6 does need waking up.

At low speeds, the throttle response reminds me of how my Mojave drove in 4L. Ok not quite, but it does have that same wind-up/spin-up surging feel to it when accelerating from a stop through the first few gears. It also has a really strong engine brake if I abruptly let off the gas while at a high RPM, which feels like a mild version of the 4xe regenerative braking mode.

 

[J0E]

Looking at a Rubicon X Unlimited with 8 spd auto. Not planning to run bigger than 35” tires but it comes with 488 gears prefer 456 which is what I have in my 84 CJ7 with LS1. Is it worth the extra bucks or should I keep looking? Think it’ll affect mileage much? If I hate it can I regear to 456 by changing ring and pinion or does it require a carrier change as well?

The keyboard crawlers here who worship the golden ratio assert that bigger tires need lower gears on a rubicon, but they don't do technical crawling. They assert you need them for the highway, which I disagree with. My JLR on 38's has stock gears and I can climb vertical in M2 (although I always shift to M1). I'm always in D7 above 45 MPH and occasionally hit D8 above 50. I sometimes take my JLR out with the buggy bunch, but normally I take my stretched LJR on sticky 43's.

If you want to technical crawl, you've already got lower gears than most technical crawlers. If you want to optimize for the highway, I'd say skip it and put the money somewhere else.

See this post where I prove the keyboard crawlers are wrong on crawling ratios. The buggy group I ride with are all on tons and 40's+. Many of them have 2.72 xfer cases, 5.38 diffs, and transmissions with much higher gears the JL's. But since the keyboard crawlers never crawl, they have no experience to go by, and they haven't done the math.

 

[wreck99]

I wonder if I should've ordered the 4.88's from the factory. It seemed like a bargain but at the same time didn't know if I needed it. Certainly not for the stock 33's. At some point, I'll be going 35s on my '24 JLUR 6MT. I just wonder how 35's will feel in the manual with stock 4.10 vs 4.88. Or if it'll be big enough to notice. I do some wheeling in between all the pavement driving.

 

[c20040215]

The keyboard crawlers here who worship the golden ratio assert that bigger tires need lower gears on a rubicon, but they don't do technical crawling. They assert you need them for the highway, which I disagree with. My JLR on 38's has stock gears and I can climb vertical in M2 (although I always shift to M1). I'm always in D7 above 45 MPH and occasionally hit D8 above 50. I sometimes take my JLR out with the buggy bunch, but normally I take my stretched LJR on sticky 43's.

If you want to technical crawl, you've already got lower gears than most technical crawlers. If you want to optimize for the highway, I'd say skip it and put the money somewhere else.

See this post where I prove the keyboard crawlers are wrong on crawling ratios. The buggy group I ride with are all on tons and 40's+. Many of them have 2.72 xfer cases, 5.38 diffs, and transmissions with much higher gears the JL's. But since the keyboard crawlers never crawl, they have no experience to go by, and they haven't done the math.

You never cease to amaze me.
3 pages of decent discussion and you showed up, first thing you did was to attack others. And brought up whole bunch of nonsense to try to build up your "credential". All those moves tell me you are extremely insecure because no one gave a crap about the points you try to make.
"The loudest one in the room is the weakest one in the room."

Your website is shit by the way.

 

[pfletcher229648]

Yeah, 220, 221, whatever it takes.

 

[word302]

You never cease to amaze me.
3 pages of decent discussion and you showed up, first thing you did was to attack others. And brought up whole bunch of nonsense to try to build up your "credential". All those moves tell me you are extremely insecure because no one gave a crap about the points you try to make.
"The loudest one in the room is the weakest one in the room."

Your website is shit by the way.

Based on his DMs with me your assessment is spot on.

 

[Old Jeeper]

Yeah, and I've had them replaced twice so far on my '22.

WHAT? Gosh, what you doing to that axle my friend?

 

[kah.mun.rah]

@nvgearhead
Not that anyone ever has diff issues,

No, never. Haha. This was our ring gear after limping it home 100 miles after breaking a tooth on the trail

 

[Ratbert]

WHAT? Gosh, what you doing to that axle my friend?

Not axle. Gears.

They're either shitty gears, shitty installs, or I'm a really, really shitty rock crawler. Take your pick.

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