5.13 or 4.88 gears

[97TJNM]

I don't buy into the altitude argument for a higher gear ratio. Having driven mine in the low altitude and flat Midwest quite a bit, there was never a time I thought the gearing should be higher.

Fair enough. I can't speak to direct experience with my jeep in lowlands. About as low as I've gotten it was 2000 feet, but it did better on the highway there. In my last pickup it did fine when I was living at sea level in Louisiana. When I moved to New Mexico, it was always hunting gears.

The 4.88 regear made a huge difference for me, but I still find myself constantly downshifting on hills here in northern NM in the mountains. And that's just to maintain speed, not pass vehicles.

YMMV.

 

[Ocho]

Fair enough. I can't speak to direct experience with my jeep in lowlands. About as low as I've gotten it was 2000 feet, but it did better on the highway there. In my last pickup it did fine when I was living at sea level in Louisiana. When I moved to New Mexico, it was always hunting gears.

The 4.88 regear made a huge difference for me, but I still find myself constantly downshifting on hills here in northern NM in the mountains. And that's just to maintain speed, not pass vehicles.

YMMV.

what's your cruising speed?

 

[97TJNM]

what's your cruising speed?

70-75.

 

[machoheadgames]

5.13 for sure on that combo. There is no reason to choose 4.88, because there is nothing 4.88 offers that 5.13 doesn’t.

 

[macleanflood]

I did 4.88s and it's pretty perfect for 33s...wish I did 5.13s cause lm going to 35s.

I do recall a post about how gears got progressively weaker the deeper you go...that 4.10 or so was the strongest and it tapered off from there.

-Mac

 

[L J]

I do recall a post about how gears got progressively weaker the deeper you go...that 4.10 or so was the strongest and it tapered off from there.

-Mac

I can recall that being forum lore many years ago. It was a thing when I had 4.88s installed in my Toyota 4x4 in the mid 90s. I put over 200,000 miles on that gearset. With the amount of 5.13, and now 5.38, gearsets running around that concern should be laid to rest.

 

[Gollywomper]

I can recall that being forum lore many years ago. With the amount of 5.13 and now 5.38 gearsets running around that claim and be laid to rest

I would think we are no where in the realm of enough HP and torque to be very concerned.

 

[RINC]

The shop that did my regear recommended 4.88 over the 5.13 I wanted saying the 4.88 was stronger than a 5.13. The 5.13 teeth being thinner than the 4.88 was their thinking.

 

[L J]

The shop that did my regear recommended 4.88 over the 5.13 I wanted saying the 4.88 was stronger than a 5.13. The 5.13 teeth being thinner than the 4.88 was their thinking.

measurably - yes
practically - no

 

[Pfarmer]

The local shop told you 4.56 because that is the correct gear for 35s and an I6…with the 3-SPEED AUTO. That is the standard chart that comes up when they search for it…I’ve seen it. Obviously, things are different for your transmission, but that default chart doesn’t say that. For your mission, 5.13 without a doubt. If it was reversed (lots of road, with a little off-road) maybe 4.88, though, 5.13 would still be a good choice. The folks on this forum know…trust them.

 

[LONGJP2]

At what point is driveshaft speed a concern?

 

[Blackjack]

At what point is driveshaft speed a concern?

When you are driving faster than you should in a lifted TJ.

Serious answer is for a TJ with quality shafts they would need to see over 4000 shaft RPM.

 

[L J]

At what point is driveshaft speed a concern?

Shawn from Tom Wood's posted here about it but I don't recall the specifics offhand.

 

[Blackjack]

Shawn from Tom Wood's posted here about it but I don't recall the specifics offhand.

This thread here. https://wranglertjforum.com/threads/drive-shaft-vibrations.63323/#post-1146048

 

[JMT]

The shop that did my regear recommended 4.88 over the 5.13 I wanted saying the 4.88 was stronger than a 5.13. The 5.13 teeth being thinner than the 4.88 was their thinking.

 

[JMT]

Here’s the page where Shawn explains harmonic vibrations and includes a driveshaft rpm calculator.

https://4xshaft.com/blogs/general-tech-info-articles/vibrations-harmonic

 

[Blake Stamper]

I have a 2.5 with 5.13s and the 30rh(3 speed auto) and sometimes feel I might have went a little too much on the gearing but at the end of the day, I gained both top end and torque, just making the motor push a bit for it, I cruise at about 3500 rpm on the freeway at 65 so nothing terrible, I don't know if I would want to hold that for an entire road trip and I definitely wouldn't drop down tire size but overall its really not that bad, I do have to say though Highway mpg is trash I get about 9-10 if I drive a lot on the highway and almost 12 if I don't touch it.

 

[Rwd1960]

I changed mine from the 4:56 to the 5:13 with Eaton e-lockers couldn't be happier on trails or highway.

 

[jjvw]

...

I do recall a post about how gears got progressively weaker the deeper you go...that 4.10 or so was the strongest and it tapered off from there.

-Mac

Assuming that is an accurate statement, lower gearing puts the mechanical advantage in favor of the gears. Meaning there is less stress on a lower gear than a higher gear in an otherwise identical rig. Our transmissions react the same way. So do multi-speed bicycles.

 

[Jerry Bransford]

The shop that did my regear recommended 4.88 over the 5.13 I wanted saying the 4.88 was stronger than a 5.13. The 5.13 teeth being thinner than the 4.88 was their thinking.

They were completely wrong and behind on their knowledge of gears. They said the same thing about 4.88 when it first came out where they were obviously wrong there too. There are a lot of us running even a lower ratio in our axles, I'm running 5.38 and they have a sterling reputation for holding up to anything dished at them.