Regear or Not

[wanderer]

So this question is for people who have 456 years from the factory I went from the factory 35 to a 37 did you re-gear or not and why?
do you notice it on the road?

If you didn’t, do you wish you had?
If you’re running on the 37 with 456 do you still see eighth?

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[kah.mun.rah]

I ran 37s with 4.10 near sea-level in SoCal for a few years and no issues. Once I moved to a higher altitude with bigger hills I changed to 4.88. If you tow, have a manual transmission, or drive a lot of hills, I would suggest a re-gear. If not, I would run the 37s with your 4.56 for a few months to see what you think before investing the $$ in a re-gear.

 

[grimmjeeper]

I ran 37s with 4.10 near sea-level in SoCal for a few years and no issues. Once I moved to a higher altitude with bigger hills I changed to 4.88. If you tow, have a manual transmission, or drive a lot of hills, I would suggest a re-gear. If not, I would run the 37s with your 4.56 for a few months to see what you think before investing the $$ in a re-gear.

I would add one thing. If possible, try driving two or three Jeeps back to back. One with 4.56 and one with 4.88 and/or 5.13. See what you think. Same engine and transmission.

I would suggest that a change from 4.56 to 4.88 is likely not going to be enough to notice. If you're going to the trouble, go to 5.13.

 

[kah.mun.rah]

For those that say re-gearing gets rid of sluggishness, my 4.88 has nearly the same acceleration my 4.10 had but it goes through the gears faster making me think it is moving a lot faster

 

[grimmjeeper]

For those that say re-gearing gets rid of sluggishness, my 4.88 has nearly the name acceleration my 4.10 had but it goes through the gears faster making me think it is moving a lot faster

The shorter (higher number) gears give a small bonus starting from a dead stop.

Once you're moving and the engine gets towards its RPM range where it makes good torque, the advantage dies off. The shift points in the automatic are programmed to keep the engine in that range. The stall speed of the torque converter makes a significant difference.

 

[TheBirdie72]

For those that say re-gearing gets rid of sluggishness, my 4.88 has nearly the name acceleration my 4.10 had but it goes through the gears faster making me think it is moving a lot faster

Above graph reminds me of…

Gear hunting like Duck hunting?

 

[JINO]

Wish they made 4.3 gears for my diesel haha.

 

[kah.mun.rah]

Above graph reminds me of…

Gear hunting like Duck hunting?

I thought I picked random colors but that proves that Nintendo has re-wired my brain.

 

[Zandcwhite]

For those that say re-gearing gets rid of sluggishness, my 4.88 has nearly the name acceleration my 4.10 had but it goes through the gears faster making me think it is moving a lot faster

Finally someone who documented and unequivocally proved what I've been saying since we bought our 2019 with this 8 speed. You won't gain back any power by changing gears. They offer no advantage anywhere but 1st gear which you only see from a dead stop because the 4.7-1 ratio is absurdly low for an auto. From the factory with 4.10s we already have the same 1st gear ratio as a TJ or early JK with 6.72 gears. With 4.56s in an xr a TJ would need 7.49 axle gears. Even on 39s the 8 speed is fantastic with 4.56s. But people get hung up on the thing holding 8th gear up hills, it's not supposed to. Non-rubicons come with 3.45s and 32" tires. That's the same ratio as 4.56s and 42" tires. Regearing an XR is a complete waste of money. If you want more power and quicker acceleration get a tune or better yet a supercharger. For the 2.0t it's even worse if you go too deep. We went from the factory 4.10s to 5.38s paired with 38s... and lost .5s 0-60 because the trans had to shift an extra time to get there. Gained .5 mpg in city driving...and lost 2mpg on the freeway.

 

[Vicrider]

There isn't much difference in rpm in top gear from a 33 and 4.10 to a 37 with 4.56

 

[grimmjeeper]

Finally someone who documented and unequivocally proved what I've been saying since we bought our 2019 with this 8 speed. You won't gain back any power by changing gears. They offer no advantage anywhere but 1st gear which you only see from a dead stop because the 4.7-1 ratio is absurdly low for an auto. From the factory with 4.10s we already have the same 1st gear ratio as a TJ or early JK with 6.72 gears. With 4.56s in an xr a TJ would need 7.49 axle gears. Even on 39s the 8 speed is fantastic with 4.56s. But people get hung up on the thing holding 8th gear up hills, it's not supposed to. Non-rubicons come with 3.45s and 32" tires. That's the same ratio as 4.56s and 42" tires. Regearing an XR is a complete waste of money. If you want more power and quicker acceleration get a tune or better yet a supercharger. For the 2.0t it's even worse if you go too deep. We went from the factory 4.10s to 5.38s paired with 38s... and lost .5s 0-60 because the trans had to shift an extra time to get there. Gained .5 mpg in city driving...and lost 2mpg on the freeway.

Over gearing is definitely not a great idea. And with the JL axles, the 5.38 pinion head diameter is too small for my tastes.

I also agree that you don't need to pull 8th gear up any significant hill.

But you really do want to get to the sweet spot where you can comfortably cruise down a flat freeway (around 65-70+) in 8th gear.

Sure, the wide spread between 1st and 8th means you won't spend much time in lower gears on the street. But having those deeper gears for off road trails is really a good thing.

So I'm all for choosing the right gear for the tires you are running. And that is absolutely influenced by the engine and transmission, not to mention the intended use of the Jeep.

Overall, with the 2.0 and automatic, either 4.88 or 5.13 is much better than 5.38. But if you're running the 3.6 with the manual and you rock crawl a lot without spending much time on high speed limit interstates, maybe 5.38 is better for the exact same tires.

There's almost never one single answer that applies universally to every Jeep.

 

[Zandcwhite]

Over gearing is definitely not a great idea. And with the JL axles, the 5.38 pinion head diameter is too small for my tastes.

I also agree that you don't need to pull 8th gear up any significant hill.

But you really do want to get to the sweet spot where you can comfortably cruise down a flat freeway (around 65-70+) in 8th gear.

Sure, the wide spread between 1st and 8th means you won't spend much time in lower gears on the street. But having those deeper gears for off road trails is really a good thing.

So I'm all for choosing the right gear for the tires you are running. And that is absolutely influenced by the engine and transmission, not to mention the intended use of the Jeep.

Overall, with the 2.0 and automatic, either 4.88 or 5.13 is much better than 5.38. But if you're running the 3.6 with the manual and you rock crawl a lot without spending much time on high speed limit interstates, maybe 5.38 is better for the exact same tires.

There's almost never one single answer that applies universally to every Jeep.

Absolutely, but looking at charts developed for old wide ratio 4-5 speed autos with 2.8-1 1st gears is a waste of time in my opinion and experience. If regearing was free I still wouldn't go deeper than 4.88s for the 39s we run on the JLUR currently. Being that the XR came with 4.56s I'll likely never do the $3k for a regear. With the 4-1 transfer case it's got an 86-1 crawl ratio from the factory which is plenty for a manual on 40s... and it's an auto and still gets an additional torque boost from the converter. With this 8 speed I found 4.56s to be perfect for 37s. Some guys still drive their rigs like an old YJ and never go over 65mph so they might as well gear to the moon. The 8 speed is forgiving on both ends but fire me the sweet spot is in the middle. There are many on here who regeared multiple times and were still disappointed because they bought the low that gearing adds back power/acceleration given up by lifts and big tires. 2 regears locally would pay for a supercharger that supercharger adds power. I'd rather have an extra 140hp and 4.10s on 37s than 5.38s or 5.13s or 4.88s and stock power. And if it's an ecodiesel or 2.0t a time is far cheaper than a regear... and will still do more for drivability. If you've got a sport with 3.45s and a 2.72 transfer case you will benefit on and off road from a regear if you go too big tires. A Rubicon not so much.

 

[grimmjeeper]

Absolutely, but looking at charts developed for old wide ratio 4-5 speed autos with 2.8-1 1st gears is a waste of time in my opinion and experience.

Agreed 100%.

If only someone made some kind of website that would generate a chart based on the exact transmission, transfer case, and tire that you have. That would be super handy.

 

[Zandcwhite]

Agreed 100%.

If only someone made some kind of website that would generate a chart based on the exact transmission, transfer case, and tire that you have. That would be super handy.

I've been using that thing for over a decade. The problem is people want to look at their JL in a vacuum. Use the comparison feature to look at something like a TJ or JK auto... and you're 4.10s are already better than the deepest gears available paired with that trans. An early JK would need Rockwell axles with 6.72 axle gears just to match the stock crawl ratio of a JLR. And yet we all ran 35s or 37s with 4.88s and got around just fine on and off road.

 

[azjl#3]

The shorter (higher number) gears give a small bonus starting from a dead stop.

Once you're moving and the engine gets towards its RPM range where it makes good torque, the advantage dies off. The shift points in the automatic are programmed to keep the engine in that range. The stall speed of the torque converter makes a significant difference.

My understanding of modern transmissions and throttle control, the torque converter really is only used from a dead stop or very slow speeds in first. Otherwise, the shifts occur so fast, the throttle is reduced while the shift occurs, and no slippage occurs and no need for the torque conv.

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