Re-gear opinions 2020 JL Wrangler Pentastar 6spd manual

floridawolfman

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I have 33" (32.8) tires. While I'd rather go with 35", I want to keep my Jeep in the garage. May go to 35" tires later on.
I adjusted my speedo input for the tires. While some people say power loss in 5th & 6th is nominal, it is significant on my wrangler, and I want to recoup some power and mileage.

PentastarV6 6-spd Manual transmission
Dana M186 Front Axle
Dana M220 Rear Axle
Conventional Differential Front & Rear Axles
(3.45 Overall Top Gear Ratio)

According to the gear chart for my application, 4.10 gears will be what I need to restore highway performance with infrequent off-road use.
Anyone else have my setup care to comment on 4.10 gears?
Getting ready to re-gear.

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Jeepjunkie

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I had your set up: sport with 3.45 gears, same tires (285/70 17) and 6 speed. m220 axle, etc.
I went with 4.56 gears and couldn’t be happier. I get 71 mph (gps verified) at 2500 revs in 6th. My fuel mileage decreased little or none (maybe 0.5 mpg) and I track it every fill up.
3rd gear is now very usable at speeds as low as 25 mph.

In my view even the 4.10s are not adequate with the 6 speed, but you could look for a rubicon with a manual to compare.

If I had to do it over again I absolutely would, maybe even 4.88s but probably stick with the 4.56s. Awesome on road and off (I wheel regularly).
 

DanW

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4.10's would be fine, but I'd go 4.56's. They'd work well with 33's but would also do well with 35's, should you upsize further, later. 4.88's, just in my humble opinion, would make the first gears a little short if you stick with 33's.

I'd find someone with a Rubicon and drive it. I think you'll like it but I think 4.56 gearing would be the sweet spot.
 

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I believe that’s the JK chart. If you’re wanting to wheel, my suggestion is to find some take out rubicon axles and run the 4.10s. If you want to move up to 35s or more you’ll be back in the same boat as it being short on power on the highway though. 4.88s are a good pairing to 35s. We have 5.13s with 37s on my 6 speed and I think it’s a great match

Brett
 
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floridawolfman

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Therby

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I have same setup as you, manual, same axles etc. Running 315/70r17 tires. 34.5”

i have 4,56 gears and I think its perfect for offroad and onroad use. 33s would be screaming on the highway at 70+ with 4.56 or more imo
 

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Can someone verify if I have the JL chart in my post?
This one says JK:

JK gear chart.jpg
We have a customer that just went home with an auto and 37s. He’s running 5.13 gears and at 70, he’s around 2300. The chart showed he should be above 2700. I have 5.13s and 6 speed and I’m sub 2500. The chart is off quite a bit. Their are calculators online that could get you closer but they still have some room for improvement.

Brett
 
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floridawolfman

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Was that based on the JK chart, or the chart I posted at the beginning of the thread that I believe to be the JL chart?
Still trying to find out if the chart I posted at the beginning of the thread is JL
 
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floridawolfman

floridawolfman

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I'm wanting to stay in the green area for "good" daily driver, full time OD, and moderate trail.
If the Chart at the beginning of the thread is JL,
It looks like 4.56 gears with 33" would work for me now if I plan on 35" later, then would keep the 35's in a good green area.

If I keep the 33's, it looks like the 4.10 will keep me in the green area where I want to be. In the 80's I had an 84 Jeep that I would've taken anywhere. I had 2 Nissan Titans and this Wrangler is now my primary Ride next to my Harley. Not planning on much trail use, so want better mileage, good daily driver and OD.
 
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Dont do 4.10. Its fine if your stock and leave it 4.10, but if your gonna spend the money at least do 4.56. Im on 4.88s 35s manual. Im at 2600 at 70 . But i can run 6th easily at 55 and get 17 . I wish i had 5.13 s it will be a far better daily driver on 4.56 than it is now.
 
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floridawolfman

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I've followed all the axle gear charts back to their origin in other threads, etc. And so far they're all JK charts. Haven't seen one that is specifically for a JL.

I found this equation to figure out gear size for new tire size on

New tire size 33" X current gear ratio 3.45 divided by original tire size 30" = 3.795

According to this, I'm closest to the 3.73 gear set. Next closest would be the 4.1 gear set.

It appears the 4.1 gear set is what I'm looking for. I have a manual trans so less power loss.

This is a baseline calc and not perfect but seems to work.
I'm wanting to re-gear and its not cheap so I want to get it right.
I do my own Harley engine work etc., did all the work on my old hot rods. I've never done or have all the tools needed for this so having a shop do it.
Any comments are appreciated if you think this is a good indicator or not.
 

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I have the same setup as you have now.

I personally would not invest in re-gearing. I just shift higher in the RPM range and I feel like I have good power. 6th gear is mostly ornamental at this point, though.
 

Oletimer

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I've followed all the axle gear charts back to their origin in other threads, etc. And so far they're all JK charts. Haven't seen one that is specifically for a JL.

I found this equation to figure out gear size for new tire size on

New tire size 33" X current gear ratio 3.45 divided by original tire size 30" = 3.795

According to this, I'm closest to the 3.73 gear set. Next closest would be the 4.1 gear set.

It appears the 4.1 gear set is what I'm looking for. I have a manual trans so less power loss.

This is a baseline calc and not perfect but seems to work.
I'm wanting to re-gear and its not cheap so I want to get it right.
I do my own Harley engine work etc., did all the work on my old hot rods. I've never done or have all the tools needed for this so having a shop do it.
Any comments are appreciated if you think this is a good indicator or not.
4.56s will have acceleration in 6th gear. I had stock 33s with factory 4.10s and it was bearable but had no real usable power in 6th.
Now with 4.88s and 35s its very nice but wish i had 5.13s.
Skip the 4.10s
 

Oletimer

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I'm wanting to stay in the green area for "good" daily driver, full time OD, and moderate trail.
If the Chart at the beginning of the thread is JL,
It looks like 4.56 gears with 33" would work for me now if I plan on 35" later, then would keep the 35's in a good green area.

If I keep the 33's, it looks like the 4.10 will keep me in the green area where I want to be. In the 80's I had an 84 Jeep that I would've taken anywhere. I had 2 Nissan Titans and this Wrangler is now my primary Ride next to my Harley. Not planning on much trail use, so want better mileage, good daily driver and OD.
Your top speed you drive your daily driver is main factor, i hardly drive over 60 because of bad traffic. With that i can pull bridges at 55mph in 6th . So to me that makes a good daily driver.
 

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