4.88/5.13 Advantages and Disadvantages

[WhatExit?]

So, aside from tire weight, you are geared 6% lower than stock. Do you like that better than stock--i.e., 37s with 4.56 gears?

stock was 4.10 and now I’m running 4.88

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[MarineHawk]

stock was 4.10 and now I’m running 4.88

Right. But 37s with 4.56 gears = stock. Read my numbers above and below, even though they aren't in the other thread. You're running 6% lower gears with 4.88 gears and 37s than with 4.1 gears and 33s. Maybe that's a good thing, and better than 37s and 4.56 gears. Just asking your opinion. You're running about 140 rpm more than stock at about 70 mph. Maybe that's a good thing. If so, I assume it's because of tire weight. But maybe not.

In case I go to 37s, I want to understand better what you’re saying. Do you mean that you are geared lower than stock overall (tires + gears), but because the 37s are heavier, it drives more like stock with the lower gearing?

The reason for my question is that, unless I’m missing something (which is more than possible):

1. Raising the tire size from the stock 32.8” (JTR) tire to 36.8” tire (e.g., Cooper 37s) increases the gearing by 12.2 %.

2. Then regearing from 4.1 gears to 4.56 gears decreases the gearing by 11.2%, which would be within 1% (1.112/1.122) of stock.

3. But regearing from 4.1 to 4.88 decreases the gearing by 19.0%, which, when increasing the tire size to 37s, would decrease the overall gearing by about 6% (1.19/1.122) from the stock overall gearing.

The 37s are heavier, which may be a reason for going to the 4.88 gears. But that gearing is lower than stock, right?

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[JP1]

I've got 4.88s with 37s.

I don't crawl.
I did it for my drive quality at highway speeds.

I think a combination of added weight, added wind resistance, added larger spin all add up to the 6% difference.

I like the feel. period.
I think I made the right choice.

 

[MarineHawk]

I've got 4.88s with 37s.
...
I did it for my drive quality at highway speeds.
I think a combination of added weight, added wind resistance, added larger spin all add up to the 6% difference.
I like the feel. period.
I think I made the right choice.

Thanks. You answered my question.

Note, the crawling (which I do) is irrelevant. When I am stopped with 35s in 4WL (with the auto trans), I am in second gear. I can't even use 1st gear unless I intentionally gear down, which I did a few times going down some nasty rocks.

 

[JP1]

I've got 4.88s with 37s.

I don't crawl.
I did it for my drive quality at highway speeds.

I think a combination of added weight, added wind resistance, added larger spin all add up to the 6% difference.

I like the feel. period.
I think I made the right choice.

so,
I think I just figured out what to do with that extra 6%...

+5.4% FTW!!!

 

[Doolin64]

In my JK, I had the boat anchor 3.8 motor and a manual. Completely different machines I know. When I lifted my JK with 35's everyone on the forums said 4:88s. I was more concerned more about highway RPMs and around town driving then I was overall crawl ratio. I ran 4:56s and couldn't have been happier. Oddly I got better gas mileage around town than I did on the highway. Im sure that's more to do with aerodynamics and weight than anything else. It seems to me my JT handles 35's with with 4:10's just fine. I have no problem reaching/staying in 8th gear on the highway if I'm just cruising along. Recalibrating my speedo made a huge difference on transmission performance. If I jump to 37's. I'll be looking at 4:56's just based on my prior experiences and what I'm seeing/feeling in my current JT with 4:10s.

 

[AJ-MJ]

TrailRecon choose 5.13 with his 38" tires.

 

[WhatExit?]

There is no right and wrong with regearing. Each Jeep is likely gonna be different - lift, tires, load carried, elevation, MOGs desired, transmission performance and terrain driven all are factors.

At the end (or beginning) of the day, you do some research, read some tables, talk to some people and read the forums and then you make a decision. Like many, selecting and installing gears isn’t inexpensive so you want to make the right choice - the one that works for you.

 

[GrayGoose]

Cruise set at 55 on flat ground running in 6th gear....shows current mpg at 19. I have 37" tires, speedo calibrated (within 1 mph of my phone) and running stock gears (It's a sport) - if I change gears to 488 or 513 can I expect to see the upper gears? Right now when going downhill with cruise at 55 it will get into 7th but on flat ground it lives in 6th.

 

[Vladiator]

TrailRecon choose 5.13 with his 38" tires.

Hey also later said he regretted it. Wished he went for 4.88’s. I think it’s on the episode where he talks about why he got rid of his gladiator. Also, I just spoke to a spicer rep. He said if you’re going with a light load on 37’s go 4:56’s. If you are close to max gross vehicle weight go for 4.88’s.

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