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What is regearing

Nicepackage

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When ppl talk about regearing due to fitting bigger tires, what does that actually mean and how do you accomplish that, at what point of tire size do you start to consider this, what are the consequences of not regearing? Thxs all for your input.
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When ppl talk about regearing due to fitting bigger tires, what does that actually mean and how do you accomplish that, at what point of tire size do you start to consider this, what are the consequences of not regearing? Thxs all for your input.
@Ole Cowboy would best describe it
 

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This topic is widely covered across Jeep and other car forums. I suggest first learning the basics of what a differential is and how it works. Gearing really is an exercise in leverage. “How much do you need?” This is much like asking a crowd of folks how much horsepower do you need... The traditional engineering response is, “That depends.” Contributing factories and design requirements are everything.

Your request is still too vague and anyone offering a quick number can’t possibly be taking your specific situation into consideration. Do a little research first and then refine your questions. You will then be better able to compare the responses you get.

Good luck building your Jeep to fit your needs.
 

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When ppl talk about regearing due to fitting bigger tires, what does that actually mean and how do you accomplish that, at what point of tire size do you start to consider this, what are the consequences of not regearing? Thxs all for your input.
A quick short answer to your question is that it means to change the gear ratio in your differentials by replacing the ring and pinion. Because we are 4 wheel drive it means doing this to the front and rear. Changing tire size affects the final drive ratio. Most people change gears to return to closely match the factory final drive ratios. The downside to not changing gears is poor performance. It generally won't hurt anything unless you made a crazy change like 30 inch to 42 inch tires. In that case it could cause drive line issues due to being way out of range in the transmission. You would likely have many other issues before you see the driveline issues with that example.
Like the other poster said, there is far more to it. Plenty of info out there.
 

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There is a formula out there but with the 3.6l I would stick with 4.11s up to 35 inch tires. And go to 4 56s with 37 inch tires.
 

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When ppl talk about regearing due to fitting bigger tires, what does that actually mean and how do you accomplish that, at what point of tire size do you start to consider this, what are the consequences of not regearing? Thxs all for your input.
Regearing means spending $2000 on an extra 150 highway RPM that won't even be noticeable on the tachometer.

It's akin to taking a bundle of $100 bills and lighting it on fire.

And before everybody flames me I will say that I have regeared sports cars and trucks and Jeeps in my own garage everything from 3.73s to 4.88s so it's not my 1st rodeo. But these days with 8- speed and 10- speed transmissions it's just not worth it anymore.
 
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Regearing means spending $2000 on an extra 150 rpm that won't even be noticeable on the tachometer.

It's akin to taking a bundle of $100 bills and lighting it on fire.

And before everybody flames me I will say that I have regeared sports cars and trucks and Jeeps in my own garage everything from 3.73s to 4.88s so it's not my 1st rodeo. But these days with 8- speed and 10- speed transmissions it's just not worth it anymore.
Good to know, thanks!
 
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When ppl talk about regearing due to fitting bigger tires, what does that actually mean and how do you accomplish that, at what point of tire size do you start to consider this, what are the consequences of not regearing? Thxs all for your input.
I have a Rubicon gladiator and I am thinking of adding the 2 and a half inch lift, would 37 inch tires be ok without a regear then?
 

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Regearing means spending $2000 on an extra 150 rpm that won't even be noticeable on the tachometer.

It's akin to taking a bundle of $100 bills and lighting it on fire.

And before everybody flames me I will say that I have regeared sports cars and trucks and Jeeps in my own garage everything from 3.73s to 4.88s so it's not my 1st rodeo. But these days with 8- speed and 10- speed transmissions it's just not worth it anymore.
I tend to agree with you on this. That said, my current Wrangler has 4.88 gears and 37’s, and it drives great. I also didn’t mind 37’s with 4.10 gears, or 35’s on 3.73, all of these in my past few Jeeps. There is definitely a limit to reasonableness though...
 

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When ppl talk about regearing due to fitting bigger tires, what does that actually mean and how do you accomplish that, at what point of tire size do you start to consider this, what are the consequences of not regearing? Thxs all for your input.
When Jeep came out with the original Rubicon it was and in fact still is one of the best-balanced rock crawlers ever built. To help you understand the why I will address the original Rubicon: One of the things talked about is Craw Ratio (CR)8: Low trans gear x Low Transfer case gear x rear axle. NOTE: IMO this is a FLAWED model as it does NOT take into account the height of the tires!

The Jeep Rubicon with OEM 31 in tires and using the 4.0L Jeep engine and 5 sp trans the ideal ratio would be about 66:1. (4x4x4.1)

NOW you have to factor: tire size (diameter) & RPM width of engine & HP curve & torque curve & weight of rig. This is where it gets dicey.

As you head towards a CR of 100:1 and beyond you are going to start needing some deep engine rpms, but you can mitigate that with taller tires, but then where is the torque/hp curve?

1) From a drive-train viewpoint, ideally, you want each set of gears (transmission, transfer case and rear axle) to within .5 +/- .5 of each other. Example: Jeep Rubicon, 4:1 1st gear, 4:1 transfer case, 4.1: rear axle, this is EXCELLENT! Why is this? Strength and equal torque distribution – multiplication of torque in the driveline! Each component is of equal relative strength and torque multiplication is equal thru the drive train (4 x 4 x 4.1 = 66). Is it acceptable to exceed these values? Certainly, just remember added stress on components will require increased strengths and may lead to premature failure of certain components.

2) Why does the Rubicon do so well off road and especially in the rocks? Crawl ratio is balanced with the ability of the Jeep engine (RPM width, torque curve, hp curve) and the Jeeps weight and it all comes together quite nicely.

You have to consider all the factors. Pull the 4.0L out of the Rubicon and put in a good engine, say a high winding V6 that does not get torquey until 2500+ RPM and its a whole different ball game as JK -JT owners might know, assuming you have spent some time behind the wheel of a TJ Rubicon with it 4.0 6.

The 4.0L delivers about 75% of its torque just past idle. Start going much beyond 3200 RPM and the engine is out of breath.

When Jeep moved to the V6 for us hardcore guys it was WTH over. All the torque and Hp is at the opposite end of the rpm curve unlike the 4.0. WHY did they do this? Because most Jeep hardcore wheeling takes place at the curb at the Sonic Drive-in. IMO Jeep should found a better engine than the V6 and it's 6000 + rpm Torque and HP curve...GRANTED the 4.0 was anemic on the highway and with 37's it was a slug.

* Craw Ration. I got no idea what Rag We B Jeep mag came up with this but it was NOT anyone who was a serious off road guy. Failure to INDEX the 'CR' is a fatal flaw because the formula does not take into account the tire diameter. Therefore take the CR and divide the tire diameter in inches into it. Do that on the TJ Rubi and you get an Index of 2.12 of a OEM TJ Rubicon. Now if you change tire sizes you can see the effects of that on performance unlike the CR was stays static and never considers tire size.

Using the 66 CR, throw on a set of 37's and you get an Index of 1.78! In other words, your 37's REDUCED your ability to perform off road...so you need to mitigate and the easy place is your rear axle ratio. In most cases you can spend as little as a few $ hundred or you can go full fu manchu and grab a set of Dynatrac ProRocks for about$12k

TO address your "HOW": This is a gear install on a JK Rubicon that wanted to run 37's so he made the jump to 4:88's.

You have several options on mitigating larger tires: Jeep has given us one by going to a multi-speed 8 gear trans, you could also regear and or add a Supercharger or all.

Take away: Adding 37's etc is a kook factor looks good as your cruise thru Sonic, but it will hurt your overall performance in an otherwise OEM Jeep especially if it is a non Rubicon with something less than a 4.10 gearset and you spend much time on a highway.

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So to boil it down a little more, transmission gear ratio x transfer case ratio x axle gear ratio = overall gear ratio.

Your tire acts as a lever at the end of the axle. Increasing the length of the lever (tire diameter) will increase your leverage but decrease the surface or rim speed of the wheel. This equates to slower acceleration in addition to increased tire weight. You can correct this by adding their more engine power or speed output or by increasing the numeric gear ratio. Moving from 4.10 to 4.88 with make up for the rotational speed difference to a degree with the goal being to return this relationship to as close to stock as possible.
 

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So to boil it down a little more, transmission gear ratio x transfer case ratio x axle gear ratio = overall gear ratio.

Your tire acts as a lever at the end of the axle. Increasing the length of the lever (tire diameter) will increase your leverage but decrease the surface or rim speed of the wheel. This equates to slower acceleration in addition to increased tire weight. You can correct this by adding their more engine power or speed output or by increasing the numeric gear ratio. Moving from 4.10 to 4.88 with make up for the rotational speed difference to a degree with the goal being to return this relationship to as close to stock as possible.
Good summation
 
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When Jeep came out with the original Rubicon it was and in fact still is one of the best-balanced rock crawlers ever built. To help you understand the why I will address the original Rubicon: One of the things talked about is Craw Ratio (CR)8: Low trans gear x Low Transfer case gear x rear axle. NOTE: IMO this is a FLAWED model as it does NOT take into account the height of the tires!

The Jeep Rubicon with OEM 31 in tires and using the 4.0L Jeep engine and 5 sp trans the ideal ratio would be about 66:1. (4x4x4.1)

NOW you have to factor: tire size (diameter) & RPM width of engine & HP curve & torque curve & weight of rig. This is where it gets dicey.

As you head towards a CR of 100:1 and beyond you are going to start needing some deep engine rpms, but you can mitigate that with taller tires, but then where is the torque/hp curve?

1) From a drive-train viewpoint, ideally, you want each set of gears (transmission, transfer case and rear axle) to within .5 +/- .5 of each other. Example: Jeep Rubicon, 4:1 1st gear, 4:1 transfer case, 4.1: rear axle, this is EXCELLENT! Why is this? Strength and equal torque distribution – multiplication of torque in the driveline! Each component is of equal relative strength and torque multiplication is equal thru the drive train (4 x 4 x 4.1 = 66). Is it acceptable to exceed these values? Certainly, just remember added stress on components will require increased strengths and may lead to premature failure of certain components.

2) Why does the Rubicon do so well off road and especially in the rocks? Crawl ratio is balanced with the ability of the Jeep engine (RPM width, torque curve, hp curve) and the Jeeps weight and it all comes together quite nicely.

You have to consider all the factors. Pull the 4.0L out of the Rubicon and put in a good engine, say a high winding V6 that does not get torquey until 2500+ RPM and its a whole different ball game as JK -JT owners might know, assuming you have spent some time behind the wheel of a TJ Rubicon with it 4.0 6.

The 4.0L delivers about 75% of its torque just past idle. Start going much beyond 3200 RPM and the engine is out of breath.

When Jeep moved to the V6 for us hardcore guys it was WTH over. All the torque and Hp is at the opposite end of the rpm curve unlike the 4.0. WHY did they do this? Because most Jeep hardcore wheeling takes place at the curb at the Sonic Drive-in. IMO Jeep should found a better engine than the V6 and it's 6000 + rpm Torque and HP curve...GRANTED the 4.0 was anemic on the highway and with 37's it was a slug.

* Craw Ration. I got no idea what Rag We B Jeep mag came up with this but it was NOT anyone who was a serious off road guy. Failure to INDEX the 'CR' is a fatal flaw because the formula does not take into account the tire diameter. Therefore take the CR and divide the tire diameter in inches into it. Do that on the TJ Rubi and you get an Index of 2.12 of a OEM TJ Rubicon. Now if you change tire sizes you can see the effects of that on performance unlike the CR was stays static and never considers tire size.

Using the 66 CR, throw on a set of 37's and you get an Index of 1.78! In other words, your 37's REDUCED your ability to perform off road...so you need to mitigate and the easy place is your rear axle ratio. In most cases you can spend as little as a few $ hundred or you can go full fu manchu and grab a set of Dynatrac ProRocks for about$12k

TO address your "HOW": This is a gear install on a JK Rubicon that wanted to run 37's so he made the jump to 4:88's.

You have several options on mitigating larger tires: Jeep has given us one by going to a multi-speed 8 gear trans, you could also regear and or add a Supercharger or all.

Take away: Adding 37's etc is a kook factor looks good as your cruise thru Sonic, but it will hurt your overall performance in an otherwise OEM Jeep especially if it is a non Rubicon with something less than a 4.10 gearset and you spend much time on a highway.

07052010675.jpeg


11052010676.jpeg


07052010674.jpg
Thxs for all the info, definitely out of my depth here, I'll try 35's with 2 inch lift
 

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Regearing means spending $2000 on an extra 150 highway RPM that won't even be noticeable on the tachometer.

It's akin to taking a bundle of $100 bills and lighting it on fire.

And before everybody flames me I will say that I have regeared sports cars and trucks and Jeeps in my own garage everything from 3.73s to 4.88s so it's not my 1st rodeo. But these days with 8- speed and 10- speed transmissions it's just not worth it anymore.
But would it be worth the money to get the extra tow with the 6 speed m/t?
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