Help with re-gearing

[Bob316]

Thanks for the advice, a lot to digest being a newbie to the Jeep world. I was thinking in the beginning to go with 4.56 gears. But was kinda talked out of it. What I gather is 33” = 4.56, 35” = 4.88 P.S I’ll be moving to Tennessee soon so I will read y’all’s advice over a couple more times. Thanks again for your input Bob316

 

[machoheadgames]

Typical fucking jerry logic. Recommends 4.56 for 33’s with the 5-speed AND 6-speed, despite the two having different overdrives that are further apart than a typical gear step, aka the difference between 4.56 & 4.88.

4.88 and 33’s with the 5-speed is LESS rpm than the 4.56 and 6-speed jerry recommends. Yet somehow 4.88 with the 5-speed is unfathomable.

Go with 4.88 for the 5-speed and 33’s. Not 4.56, and definitely not 4.10. Keep in mind jerry hasn’t had a 5-speed in something like 16 years.

If 35’s are in the future, go for 5.13.

 

[JMT]

4.56 is the correct gear for an AX15 trans with 33’s, which is the transmission being discussed. 5.13 is for the 42RLE

https://wranglertjforum.com/threads...angler-tj-lj-and-other-re-gearing-faqs.17063/

Do you know why that chart is wrong?

AX-15 left, NV3550 (wide ratio) right. Now tell me why the chart you linked to says 4.56 for the AX-15 and 4.88 for the NV3550. Everyone needs to get over the bogus 4.56 recommendation. 4.88 is the only way to go for 33’s on both 5-speed transmissions that are virtually identical. Geez.

 

[Painfultruth]

Do you know why that chart is wrong?

AX-15 left, NV3550 (wide ratio) right. Now tell me why the chart you linked to says 4.56 for the AX-15 and 4.88 for the NV3550. Everyone needs to get over the bogus 4.56 recommendation. 4.88 is the only way to go for 33’s on both 5-speed transmissions that are virtually identical. Geez.

View attachment 513618

Educate me…

 

[machoheadgames]

Educate me…

If you need to be educated, why are you giving advice?

4.56 and 33’s is good with the 6-speed. It was known as “good” with the 5-speeds for many years, but that’s because the lowest available ratio was 4.88 and so everybody set 35’s to 4.88 and adjusted all the other tire sizes accordingly. In reality, with a 5-speed that has a taller OD and worse/wider gear spread, 4.88 is a better choice for 33’s.

The problem is that someone who is practically worshipped here says otherwise, and that is hard to overcome.

 

[Painfultruth]

If you need to be educated, why are you giving advice?

4.56 and 33’s is good with the 6-speed. It was known as “good” with the 5-speeds for many years, but that’s because the lowest available ratio was 4.88 and so everybody set 35’s to 4.88 and adjusted all the other tire sizes accordingly. In reality, with a 5-speed that has a taller OD and worse/wider gear spread, 4.88 is a better choice for 33’s.

The problem is that someone who is practically worshipped here says otherwise, and that is hard to overcome.

4.88 4.56

At the sacrifice of efficiency, which is often overlooked. Driving conditions are a factor.

As pointed out the environment is better suited for maximizing fuel economy than max power.

 

[machoheadgames]

4.88 4.56
View attachment 513646

At the sacrifice of efficiency, which is often overlooked. Driving conditions are a factor.

As pointed out the environment is better suited for maximizing fuel economy than max power.

View attachment 513645

That chart is for 55 miles per hour with no overdrive. Not helpful. Efficiency is typically the same between the two ratios, 200 rpm makes very little difference in mpg.

Again, you have a 6-speed and 4.56 with it is equivalent on the highway to a 5-speed with 4.88. If you are happy with what you have, then you should be recommending 4.88 for the 5-speed owners.

The thread you linked to earlier is wrong. AX15 & NV3550 should receive the same gearing advice while the 6-speed does okay with one gear ratio taller due to having less of an overdrive.

 

[jjvw]

4.88 for the 5 speed and 33s. Florida is irrelevant.

 

[jjvw]

Typical fucking jerry logic. Recommends 4.56 for 33’s with the 5-speed AND 6-speed, despite the two having different overdrives that are further apart than a typical gear step, aka the difference between 4.56 & 4.88.

4.88 and 33’s with the 5-speed is LESS rpm than the 4.56 and 6-speed jerry recommends. Yet somehow 4.88 with the 5-speed is unfathomable.

Go with 4.88 for the 5-speed and 33’s. Not 4.56, and definitely not 4.10. Keep in mind jerry hasn’t had a 5-speed in something like 16 years.

If 35’s are in the future, go for 5.13.

If this were a 32rh, Jerry would be recommending a higher final drive rpm because he has never run the numbers to understand how the gearing, tire sizes and transmission options actually compare to each other to develope any consistency for what axle gearing to suggest.

 

[machoheadgames]

If this were a 32rh, Jerry would be recommending a higher final drive rpm because he has never run the numbers to understand how the gearing, tire sizes and transmission options actually compare to each other to develope any consistency for what axle gearing to suggest.

Yep.

And, for many years, locations such as Florida didn’t matter to him, yet now all of a sudden that matters.

 

[BlueC]

In Florida, he'll have to deal with tire drag, wind drag, and bug drag ( thanks, @BlueC ). That's got to be pretty equivalent. Anybody ever calculate bug drag?

When you travel through the swampy center, if you can see through the windshield, bug-drag is at an acceptable level. If you can't see, bug-drag is excessive.

 

[JMT]

4.88 4.56
View attachment 513646

At the sacrifice of efficiency, which is often overlooked. Driving conditions are a factor.

As pointed out the environment is better suited for maximizing fuel economy than max power.

View attachment 513645

It’s not that fuel economy is overlooked, it’s that any difference is immeasurable. I’ve had four different gear ratio and tire size setups that have been in green, yellow, and red and can never tell a difference. I have records compiled since January 2017.

What is measurable is downshifting because RPM’s in the 2500 range are not enough to hold 70mph or pass a vehicle.

As stated ad nauseum about the 5 and 6 speed, they should never be given the same recommendation. The numbers tell all. The Original Poster is throwing away good money gearing to 4.56 or 4.10. As usual a shop steered him away from 4.56 to 4.10. That means he should look for a different shop. This one is clueless on a transmission’s relationship to a gear ratio.

 

[BlueC]

It’s not that fuel economy is overlooked, it’s that any difference is immeasurable. I’ve had four different gear ratio and tire size setups that have been in green, yellow, and red and can never tell a difference

That's something that many people can't seem to square in their heads. RPM has very little effect on fuel consumption. Load demand (throttle input/position) dictates fuel usage.

 

[Rickyd]

That's something that many people can't seem to square in their heads. RPM has very little effect on fuel consumption. Load demand (throttle input/position) dictates fuel usage.

Gas motors are much more forgiving of rpms with fuel consumption. Diesels not as much.

Another problem with that chart is it doesn't refer to a specific motor in a specific vehicle. There is no way motive gear has done fuel consumption dyno tests on a tj with varying gears to see which ratio burns less fuel per hr. Or took into consideration of the first gear and setting up a decent crawl ratio.

The main reason i never point to these charts is they give no context.

 

[por212]

Should we really select gears for Jeeps with manual transmissions based on the ability to overtake another vehicle at 70 mph without the need to downshift when in OD? The downshift from OD when accelerating feature has always been included in automatic transmissions. There are a number of things to consider when selecting gears but cannot see where this would be valid.

 

[jjvw]

Should we really selected gears for Jeeps with manual transmissions based on the ability to overtake another vehicle at 70 mph without the need to downshift when in OD? The downshift from OD when accelerating feature has always been included in automatic transmissions. There are a number of things to consider when selecting gears but cannot see where this would be valid.

That falls within the realm of overall drivability. We generally would like a Jeep that can get out of it's own way.

As someone who has been through a multiple combinations of tire sizes, axle gearings and transmissions on the same Jeep that has also traveled extensively through many regions of the country, I have yet to find a scenario where less rpm from gearing would have somehow been preferable.

With that said, I have been pushing, with calculations, 3k rpm at 75mph for many years. Jerry has been pushing against that for just as many years. This is based on many years and many miles of experience.

Yet the reality is that the early TJ with the 32rh was released from the factory with even lower gearing and a higher final gear rpm than what I have been advocating. Which suggests that for 25 years, very few have been regearing deep enough compared to what Jeep was doing from the very start.

One of the foundations of my personal build saga has been drivability, both on and off road. A continual conclusion for 10 years on this has been that the two are not at all mutually exclusive. Lower gears and higher rpms are nearly always a preferable goal to strive for.

 

[ColoJeep]

4.88 is proper for 33’s and the 5-speed. 4.56 is proper for 33’s and the 6-speed

Should we really selected gears for Jeeps with manual transmissions based on the ability to overtake another vehicle at 70 mph without the need to downshift when in OD?

This is what what happens when the 2 pedal group think is overlayed on the manual transmission group. Does anyone think you should gear a Hayabusa or Ninja's final drive ratio to give max accelaration at 70 m.p.h. without downshifting ? Not likely . Of course I chuckle when I read about passing cars at 70+ in a TJ . Kinda like bring a dull knife to a gun fire fight.

 

[jjvw]

This is what what happens when the 2 pedal group think is overlayed on the manual transmission group. Does anyone think you should gear a Hayabusa or Ninja's final drive ratio to give max accelaration at 70 m.p.h. without downshifting ? Not likely . Of course I chuckle when I read about passing cars at 70+ in a TJ . Kinda like bring a dull knife to a gun fire fight.

Apples to oranges comparison. We aren't driving motorcycles, let alone a vehicle with a remotely comparable horsepower to weight ratio to anything remotely considered high performance.

But even if we were, we would still be thoughtful of the gearing as it relates to the overall build and the overall drivability.

Former manual transmission guy here, btw.

 

[RHanna]

Hello all, a question for all you guys who know about gearing. I have a 99 tj with 3.07 gears, I want to change to 4.10 will I need a bigger carrier to do this ? Thanks Bob316

What is the probably that you stay with 33? If it isn't 100% I'd plan for 35 gearing. What part of TN? West TN is relatively flat. How often do you plan on driving at highway speeds?

 

[Prolabywill]

Thanks for the advice, a lot to digest being a newbie to the Jeep world. I was thinking in the beginning to go with 4.56 gears. But was kinda talked out of it. What I gather is 33” = 4.56, 35” = 4.88 P.S I’ll be moving to Tennessee soon so I will read y’all’s advice over a couple more times. Thanks again for your input Bob316

Hey Bob. Curious how much the rehear cost you? I’d like to do same but I’m sure it’s out of my price range.