Switching gears - long 4th gear

SCRubicon23

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Have a dumb question and any answers would be appreciated. My JT(auto) goes through 1st, 2nd, and 3rd gear normal but 4th gears is long(high rpms) before finally shifting into 5th. It is a Rubicon the gears are 4:1 and I know that’s a little different but I have a JLUR also and I’ve never noticed it in it. I only have 300 miles on it so maybe it just needs to be broken in more. I don’t know.



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Alabama Mud Machine

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The 4:1 ratio is in your transfer case, and is only applicable when you're locked in 4wd.

Also, the 8-speed auto has 2 overdrives (7th & 8th). 6th gear is your 1:1 ratio.

Your 4th gear might seem "taller" because from 5th through 8th are much closer (smaller) ratio gaps.

  • Gear Ratios:
    • 1st - 4.71
    • 2nd - 3.13
    • 3rd - 2.10
    • 4th - 1.67
    • 5th - 1.28
    • 6th - 1.00
    • 7th - 0.84
    • 8th - 0.67
    • Reverse - 3.53
 
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SCRubicon23

SCRubicon23

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The 4:1 ratio is in your transfer case, and is only applicable when you're locked in 4wd.

Also, the 8-speed auto has 2 overdrives (7th & 8th). 6th gear is your 1:1 ratio.

Your 4th gear might seem "taller" because from 5th through 8th are much closer (smaller) ratio gaps.

  • Gear Ratios:
    • 1st - 4.71
    • 2nd - 3.13
    • 3rd - 2.10
    • 4th - 1.67
    • 5th - 1.28
    • 6th - 1.00
    • 7th - 0.84
    • 8th - 0.67
    • Reverse - 3.53
Appreciate the response but that’s like reading Chinese for me.
 

Alabama Mud Machine

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I've been told that a lot by A LOT of people. I like technical specs, because most of my hobbies (like building offroad trucks, or loading ammo for long range precision shooting) require extremely specific responses, or it could cause a problem, or get someone hurt from a malfunction.

I don't know of any other way to explain it in any other form... Maybe someone else can chime in.
 

JTPatriot

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Yes, Rubicons come with 4.10:1 differentials and the transfer case has the 4:1 gear ratio. I think the OP was meaning that with his 4:1 but meant 4.10:1.

Have to be careful with and where you use ( : ) and ( . ). Man that kind of looks dirty.
 

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Yes, Rubicons come with 4.10:1 differentials and the transfer case has the 4:1 gear ratio. I think the OP was meaning that with his 4:1 but meant 4.10:1.

Have to be careful with and where you use ( : ) and ( . ). Man that kind of looks dirty.
That might have been what he meant, but I thought he was referring to the crawl ratio in the t-case affecting his final drive ratio... My bad. Yes, correct. the Rubicon diffs have a 4.10:1 ratio, but the t-case on the Rubicon has a 4:1 crawl ratio, as well. Thanks for clarifying that for him.
 

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Thanks for the clarification.

My Sport S with Max Towing also has the 4:10 gears. As I understand it, the trans will adapt to your driving habits which affects the shifts. I would suggest giving it some time to break-in and keep learning. I never noticed my trans hanging onto 4th gear. It accelerates quite nicely.
 

redrider

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The listing of the individual gearing ratios is a way of visualizing the engine crankshaft/transmission input shaft rotation compared to the transmission output shaft/driveshaft rotation. The first gear ratio of 4.71 means for every turn of the output shaft, the engine crankshaft revolves 4.71 times. Another conversion is applied to that info about final drive/differential gearing and transfer case crawl ratio (4.10, 4:1 respectively)
 

TREDpunk

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Little over 400 miles on my Max Tow and I’ve noticed the same thing. Seems to like 4th though you don’t go too high RPM.
 

Texops

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i noticed this since i went to 37" tires from 35's and i have 373 gears the Jeep probably thinks i'm towing since i have heavy tires & it holds 4th until i get up to speed then it goes 5th & 6th. re-gearing tomorrow.
 

Icebird1976

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I've been experiencing this SAME exact thing ever since I took delivery (December 23rd) . I have a stock Rubicon with only 2200 on the clock. It's not so bad on flat roads, but I experience it most on my little local mountain roads. 4th does seem to wind out a lot longer, sometimes going to almost 4k rpm. I'm not hard on the truck, and I know that the truck has more than enough power to pull a little incline.
I've also noticed that it holds onto 4th coasting downhill, too. As the speed builds, under no engine load, it should easily go into 5th. But it just hangs there, sometimes going over 4500 rpm before shifting up.
In either situation, I tolerate it for a little while. And sometimes I'll shift manually, just to avoid the issue altogether. I don't think anything is wrong, but I've always thought of it as a little odd that it holds 4th so long... unnecessarily long.
 

LostWoods

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Appreciate the response but that’s like reading Chinese for me.
It's gear reduction ratios. Those numbers are how many rotations of the engine (technically transmission input shaft since the torque converter can eat some of the engine RPMs) it takes to get a single rotation of the transmission's output shaft. Bigger numbers substnantially increase torque but mean lower ground speed at any given RPM, lower numbers give higher speed at any given RPM for cruising at the cost of reduced power.

It applies all the way back so a 4:1 transfer case means that in 4Lo, you need 4 rotations of the input shaft to get one rotation of the output. With a 4.10 rear end, you need 4.10 rotations of the pinion/driveshaft to get one rotation from the axles and tires. It's linear multiplication out so it's pretty easy to calculate.

So in first gear, 4wd low on a Rubicon, you have a 4.71:1 transmission gear, 4:1 transfer case gears, and 4.10:1 rear end gearing. that means you need 77.244 rotations (4.71*4.0*4.1) of the engine to get a single rotation of the rear axle and tires. This is called the crawl ratio and it's the lowest ratio (highest numerically) you can get out of the truck.

Inversely, in 8th gear, you have a 0.67:1 transmission gear, 1:1 transfer case, and the same 4:10:1 rear end. That means you only need 2.747 (0.67*1.0*4.10engine rotations to get a complete rotation of the rear axle and tires. This is the cruise ratio and it's the tallest (lowest numerically) you can get.

To answer your original question, I'm fairly certain it's all in the programming beacuse I've found my truck does not like to be in 5th unless I really peg it on the freeway where it comes down to 5th from 7th/8th. It seems to hold 4th pretty consistently then go a very quick 4-5-6 cruising around at 55mph and it's only grown worse since upgrading to 35's.
 
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It's gear reduction ratios. Those numbers are how many rotations of the engine (technically transmission input shaft since the torque converter can eat some of the engine RPMs) it takes to get a single rotation of the transmission's output shaft. Bigger numbers substnantially increase torque but mean lower ground speed at any given RPM, lower numbers give higher speed at any given RPM for cruising at the cost of reduced power.

It applies all the way back so a 4:1 transfer case means that in 4Lo, you need 4 rotations of the input shaft to get one rotation of the output. With a 4.10 rear end, you need 4.10 rotations of the pinion/driveshaft to get one rotation from the axles and tires. It's linear multiplication out so it's pretty easy to calculate.

So in first gear, 4wd low on a Rubicon, you have a 4.71:1 transmission gear, 4:1 transfer case gears, and 4.10:1 rear end gearing. that means you need 77.244 rotations (4.71*4.0*4.1) of the engine to get a single rotation of the rear axle and tires. This is called the crawl ratio and it's the lowest ratio (highest numerically) you can get out of the truck.

Inversely, in 8th gear, you have a 0.67:1 transmission gear, 1:1 transfer case, and the same 4:10:1 rear end. That means you only need 2.747 (0.67*1.0*4.10engine rotations to get a complete rotation of the rear axle and tires. This is the cruise ratio and it's the tallest (lowest numerically) you can get.

To answer your original question, I'm fairly certain it's all in the programming beacuse I've found my truck does not like to be in 5th unless I really peg it on the freeway where it comes down to 5th from 7th/8th. It seems to hold 4th pretty consistently then go a very quick 4-5-6 cruising around at 55mph and it's only grown worse since upgrading to 35's.
Same here. I wrote the original post before I purchased new wheels and 35” tires. It’s worse now.
 

hjdca

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If I had an automatic, and if I had a Tazer, I would play with the tire size parameter and the rear end gear ratio parameter to see if I could get the JT to shift where I wanted.
 
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