Considering a future re-gear, need advice

[GregBelleville]

10% gear change roughly. It’s not going to go from a dog to amazing with one gear step. It will of course be an improvement.

I remember having this discussion with you in the past. You might need to do a few things, like check your cats for clogging, adjust the transmission bands, etc. There may be something making yours not drive so great - something more than just 3” larger tires. I would definitely recommend the regear but from how you describe yours driving, I wouldn’t expect a 10% regear to fix everything. That said, I wouldn’t regear extra deep to make up for it either. I like lower gears than most but I wouldn’t want 4.56 on 33’s permanently with the 3 speed.

Did you ever use GPS to verify your actual speed and what rpm you're at at each speed? How did you confirm you have 3.73?

I confirmed I had 3.73s when I changed my gear oil a few months ago. I didn't realize that was you I had asked for gearing advice a while back. I think my comments about how much of a dog I thought it was was said out of inexperience driving a TJ on bigger tires. As I've driven it more I've gotten more used to it's driving behavior and while it's no sports car, it can drive comfortably at 70mph, but if I hit a hill on the highway it definitely struggles to hold speed. I did use my phone to confirm my Speedo was accurate.

 

[Jerry Bransford]

This “before & after” data should confirm if your current gears are 3.07 & also what 4.56 gears will do for you. You just need an old portable GPS or maybe some kind of phone app that does the same thing. Freeway mile markers coming by at a mile per minute is also 60 mph.
Personally, If I were going with 31” tires I would use 4.10 gears, but that’s just me.
While the gears are being changes it’s a great time to also install chromoly axle shafts & either lockers or limited slips. Doing that at the same time will save a lot of labor costs.
Good luck!

View attachment 473987

Those RPMs, 2800 at 65mph with 4.56 gears and 33" tires, are not correct for the 5-speed the OP has. With the 5-speed AX-15 the OP has, 4.56 would produce more like 2420 RPMs at 65 mph.

This is showing the RPMs with the transmission set for a the OP's AX-15 transmission, 4.56 axle ratio, and 33" tires which typically measure out more close 32.5" which is what I used for this calculation. This was produced with the gearing page at http://www.grimmjeeper.com/gears.html

 

[2005rubiconTJR]

STRENGTH ONLY QUESTION- Is a 410gear set stronger than a 513 running same size and weight tires? My buddy runs 410 or 411 Rubicon (2006 manual) and is leaving them in to do a rubicrawler or atlas. He said the 411 is stronger because there bigger and after carbon axle shafts the gears are the weak part in the axle. He's not that good of a friend so be free to be real honest

 

[machoheadgames]

STRENGTH ONLY QUESTION is a 410gear set stronger than a 513 running same size and weight tires. My buddy runs 410 or 411 Rubicon (2006 manual) and is leaving them to do a rubicrawler or atlas he said the 411 is stronger. He's not that good of a friend so be free to be real honest

The strength difference doesn’t matter due to leverage.

 

[Rickyd]

STRENGTH ONLY QUESTION is a 410gear set stronger than a 513 running same size and weight tires. My buddy runs 410 or 411 Rubicon (2006 manual) and is leaving them to do a rubicrawler or atlas he said the 411 is stronger. He's not that good of a friend so be free to be real honest

He's an idiot. You can't run in low range down the highway in a practical manner

 

[2005rubiconTJR]

He's an idiot. You can't run in low range down the highway in a practical manner

Obviously but he could run down the hwy in high range without any issues. Is it stronger or not? Could you explain the leverage theory please?

 

[machoheadgames]

Obviously but he could run down the hwy in high range without any issues. Is it stronger or not? Could you explain the leverage theory please?

The lower the gear ratio (aka 5.13 vs 4.10), the less stress on the teeth, due to leverage. Think about it on a bike. Put it on the small chainring up front and the large sprocket out back. You will pedal a bunch of times and not go very far or very fast. It will take almost no effort to move the pedals. As such, the chain is under very little load.

Put the bike chain on the largest chainring and the smallest sprocket. You'll move 10 feet with one pedal rotation and the pedals will require very high load to get moving. If you were starting from a stop, you will nearly be standing on the pedals and pulling on the handlebars to put the necessary force into the pedals to get moving.

The R&P follow the same principal. The 5.13 gear set sees less load on the teeth, similar to the first bike setup. The driveshaft/engine rpm will be higher to go the same speed, but the load on the drivetrain upstream of the gears will be less and therefore the load through the gear teeth themselves will also be less. With 4.10, it will be closer to the second bike scenario. The bike scenarios are meant to be dramatic to get the point across.

Therefore....the strength of the teeth doesn't really matter. It's more about the load the teeth see. If your tires are sized appropriately for the axle and you exercise proper use of the throttle, then what ratio you choose isn't critical as far as strength is concerned.

To choose 4.10 over 5.13s simply because of strength is dumb. Also don't forget that the gear companies both sell and warranty all the gearsets and they don't put large disclaimers on them that you must run X tire size or smaller on certain ratios or else the warranty will not be upheld.

 

[2005rubiconTJR]

The lower the gear ratio (aka 5.13 vs 4.10), the less stress on the teeth, due to leverage. Think about it on a bike. Put it on the small chainring up front and the large sprocket out back. You will pedal a bunch of times and not go very far or very fast. It will take almost no effort to move the pedals. As such, the chain is under very little load.

Put the bike chain on the largest chainring and the smallest sprocket. You'll move 10 feet with one pedal rotation and the pedals will require very high load to get moving. If you were starting from a stop, you will nearly be standing on the pedals and pulling on the handlebars to put the necessary force into the pedals to get moving.

The R&P follow the same principal. The 5.13 gear set sees less load on the teeth, similar to the first bike setup. The driveshaft/engine rpm will be higher to go the same speed, but the load on the drivetrain upstream of the gears will be less and therefore the load through the gear teeth themselves will also be less. With 4.10, it will be closer to the second bike scenario. The bike scenarios are meant to be dramatic to get the point across.

Therefore....the strength of the teeth doesn't really matter. It's more about the load the teeth see. If your tires are sized appropriately for the axle and you exercise proper use of the throttle, then what ratio you choose isn't critical as far as strength is concerned.

To choose 4.10 over 5.13s simply because of strength is dumb. Also don't forget that the gear companies both sell and warranty all the gearsets and they don't put large disclaimers on them that you must run X tire size or smaller on certain ratios or else the warranty will not be upheld.

That is a fantastic explanation Thank you!!!

 

[Rickyd]

he could run down the hwy in high range without any issues.

depending on tire size his overdrive will be severely underpowered and overgeared. That isn't no issues to me

 

[Artsifrtsi]

The lower the gear ratio (aka 5.13 vs 4.10), the less stress on the teeth, due to leverage. Think about it on a bike. Put it on the small chainring up front and the large sprocket out back. You will pedal a bunch of times and not go very far or very fast. It will take almost no effort to move the pedals. As such, the chain is under very little load.

Put the bike chain on the largest chainring and the smallest sprocket. You'll move 10 feet with one pedal rotation and the pedals will require very high load to get moving. If you were starting from a stop, you will nearly be standing on the pedals and pulling on the handlebars to put the necessary force into the pedals to get moving.

The R&P follow the same principal. The 5.13 gear set sees less load on the teeth, similar to the first bike setup. The driveshaft/engine rpm will be higher to go the same speed, but the load on the drivetrain upstream of the gears will be less and therefore the load through the gear teeth themselves will also be less. With 4.10, it will be closer to the second bike scenario. The bike scenarios are meant to be dramatic to get the point across.

Therefore....the strength of the teeth doesn't really matter. It's more about the load the teeth see. If your tires are sized appropriately for the axle and you exercise proper use of the throttle, then what ratio you choose isn't critical as far as strength is concerned.

To choose 4.10 over 5.13s simply because of strength is dumb. Also don't forget that the gear companies both sell and warranty all the gearsets and they don't put large disclaimers on them that you must run X tire size or smaller on certain ratios or else the warranty will not be upheld.

Gear ratio debates have been going on for decades... and the bicycle comparison always comes up, and fails to properly explain the weaknesses. Yes, the bicycle gear example does affect stresses... it affects the stresses on the entire drivetrain, not the gears themselves.

Lower gearsets have larger ring gears (mainly only thicker) and smaller pinions (diameter). With the smaller diameter pinion, you have less teeth to engage into the ring. Where the lower gears fail before a higher gear, is when you get a shock load... IE spinning a tire, then all of the sudden getting traction on that tire. The smaller surface area will lose, and fail, before a higher surface area will.

 

[Jeepster97TJ]

So I ran down the highway at 60 mph (using GPS). I maintained that in 4th gear @2000rpm. By my calculations (3.22-3.27 depending on the exact tire size) thats in the neighborhood of 3.07. How should it be feeling? It takes off easy and it doesn't chug along. My speedo is way off due to the fact they never changed the speedo gearing. Which based on my tire size and gearing there isn't an gear for me unless I change axle gearing or come down in tire size. When I bought the Jeep I drove it from Alabama to South Carolina and I ran 65-70 most of the way in 5th gear. Occasionally having to down shift. This is my first Jeep but I am no stranger to manual trans. I know what it feels like when a vehicle is struggling. Taking off up a hill from dead stop to running down the highway seem normal.

Really the only reason I bring up the gearing is the speedo being way off and considering tire down size. If I am truly running stock gearing it should only get better by going down to 31x10.5R15's. The tires I have are M/T and they are loud going down the road. I wanted to trade them but learned they are too old by date so I will run them til I have an issue. They have been in storage in a garage under a cover since 2012. They look brand new (no uv cracking or dry rot), but since I only do in town driving I figure I will keep an eye on them for now.

 

[Artsifrtsi]

So I ran down the highway at 60 mph (using GPS). I maintained that in 4th gear @2000rpm. By my calculations (3.22-3.27 depending on the exact tire size) thats in the neighborhood of 3.07. How should it be feeling? It takes off easy and it doesn't chug along. My speedo is way off due to the fact they never changed the speedo gearing. Which based on my tire size and gearing there isn't an gear for me unless I change axle gearing or come down in tire size. When I bought the Jeep I drove it from Alabama to South Carolina and I ran 65-70 most of the way in 5th gear. Occasionally having to down shift. This is my first Jeep but I am no stranger to manual trans. I know what it feels like when a vehicle is struggling. Taking off up a hill from dead stop to running down the highway seem normal.

Really the only reason I bring up the gearing is the speedo being way off and considering tire down size. If I am truly running stock gearing it should only get better by going down to 31x10.5R15's. The tires I have are M/T and they are loud going down the road. I wanted to trade them but learned they are too old by date so I will run them til I have an issue. They have been in storage in a garage under a cover since 2012. They look brand new (no uv cracking or dry rot), but since I only do in town driving I figure I will keep an eye on them for now.

If it's like mine, when your speedo is indicating 60mph, you should be about 69mph (ish) with 3.07 and in OD. (some differences between your 5sp and my 6sp)

When I run the grim jeeper calculator on mine, to get back to the same RPM as with the stock 215 tires, I need about a 3.8 ratio... I'll go to the 4.11, which will give me about 250 more RPM than stock at 70.

 

[machoheadgames]

So I ran down the highway at 60 mph (using GPS). I maintained that in 4th gear @2000rpm. By my calculations (3.22-3.27 depending on the exact tire size) thats in the neighborhood of 3.07. How should it be feeling? It takes off easy and it doesn't chug along. My speedo is way off due to the fact they never changed the speedo gearing. Which based on my tire size and gearing there isn't an gear for me unless I change axle gearing or come down in tire size. When I bought the Jeep I drove it from Alabama to South Carolina and I ran 65-70 most of the way in 5th gear. Occasionally having to down shift. This is my first Jeep but I am no stranger to manual trans. I know what it feels like when a vehicle is struggling. Taking off up a hill from dead stop to running down the highway seem normal.

Really the only reason I bring up the gearing is the speedo being way off and considering tire down size. If I am truly running stock gearing it should only get better by going down to 31x10.5R15's. The tires I have are M/T and they are loud going down the road. I wanted to trade them but learned they are too old by date so I will run them til I have an issue. They have been in storage in a garage under a cover since 2012. They look brand new (no uv cracking or dry rot), but since I only do in town driving I figure I will keep an eye on them for now.

33's measure around 31.5" typically. That comes out to 1964 rpm at 60 mph in 4th. Matches perfectly to what you're seeing.

You'd be surprised at the increase of available torque going down to 31's and then also changing gears from 3.07 to 4.10 or 4.56. It's hard to describe especially when it feels normal enough already that you don't think it's "bad", but that all changes once you drive a lower geared setup. You might be able to find someone near you that you could test drive their Jeep and get an idea of the difference.

The main thing I don't like about tall gears like 3.07 is that it handicaps all the gears and prevents them from being usable at the times when you need them to be. Putting around town is not such a big deal, but when you're on the highway, 3.07 makes it difficult to find a good gear for passing. For example, 2nd gear maxes out at 65-70 so you wouldn't use it, 3rd gear is way down at 3300 rpm @70, which is fine itself for passing but won't have much get up and go if you need it. 4th is already a low rpm gear and 5th is practically unusable. It's much easier to use your transmission gearset when the axle gears are low enough to allow the transmission gears to rev up appropriately.

 

[machoheadgames]

Gear ratio debates have been going on for decades... and the bicycle comparison always comes up, and fails to properly explain the weaknesses. Yes, the bicycle gear example does affect stresses... it affects the stresses on the entire drivetrain, not the gears themselves.

Lower gearsets have larger ring gears (mainly only thicker) and smaller pinions (diameter). With the smaller diameter pinion, you have less teeth to engage into the ring. Where the lower gears fail before a higher gear, is when you get a shock load... IE spinning a tire, then all of the sudden getting traction on that tire. The smaller surface area will lose, and fail, before a higher surface area will.

While that can be true, this is where the argument of "do you have enough axle" comes in....if you keep your tire sizes to the recommended limits, you usually won't have trouble. Like 35's for Dana 44, etc. The lower gears themselves are slightly weaker and a shock load may be more likely to kill them, but it's not likely to happen if the axle is sized appropriately. We have a bunch of regeared members here running 5.13-5.38 gears and there are very little troubles with many of those owners going offroad in the rocks.

On the flip side, the gear teeth on the lower gearsets will see less forces on the teeth from driving, whether that's offroad or onroad. For the most part, gear size related to ratios seems mostly irrelevant and still, that's why warranties exist. The companies are still selling them, so they can't be failing too often or they would put a stop to that pretty quick.

 

[Artsifrtsi]

While that can be true, this is where the argument of "do you have enough axle" comes in....if you keep your tire sizes to the recommended limits, you usually won't have trouble. Like 35's for Dana 44, etc. The lower gears themselves are slightly weaker and a shock load may be more likely to kill them, but it's not likely to happen if the axle is sized appropriately. We have a bunch of regeared members here running 5.13-5.38 gears and there are very little troubles with many of those owners going offroad in the rocks.

On the flip side, the gear teeth on the lower gearsets will see less forces on the teeth from driving, whether that's offroad or onroad. For the most part, gear size related to ratios seems mostly irrelevant and still, that's why warranties exist. The companies are still selling them, so they can't be failing too often or they would put a stop to that pretty quick.

And not too many failures, because the majority of offroaders are not in the "send-it" mentality, and those that are (and do it smartly) have gon up to bigger axles to make those failure parts larger and stronger...

(gotta drive that hooptie back home...)

 

[PNW_LJ]

And not too many failures, because the majority of offroaders are not in the "send-it" mentality, and those that are (and do it smartly) have gon up to bigger axles to make those failure parts larger and stronger...

(gotta drive that hooptie back home...)

Even then, if you look at some of the big tire, high horsepower rock bouncers running tons/unimogs/etc, you’ll often see them running tall diff ratios like 4.10.

 

[Jerry Bransford]

If it's like mine, when your speedo is indicating 60mph, you should be about 69mph (ish) with 3.07 and in OD. (some differences between your 5sp and my 6sp)

When I run the grim jeeper calculator on mine, to get back to the same RPM as with the stock 215 tires, I need about a 3.8 ratio... I'll go to the 4.11, which will give me about 250 more RPM than stock at 70.

The goal should never be to gear to get the same rpms with bigger tires that worked well for smaller tires. Bigger tires require more rpms because they are harder to turn due to their larger diameter which give them more leverage against the drivetrain.

 

[Artsifrtsi]

The goal should never be to gear to get the same rpms with bigger tires that worked well for smaller tires. Bigger tires require more rpms because they are harder to turn due to their larger diameter which give them more leverage against the drivetrain.

If that's what you read by my statement, you should re-read... I said to get back to the same RPM I need ~3.8:1... and I'm going with 4.11:1.

<joke> and what is rpms? It's RPM... Revolutions (plural is there already) Per Mile... )</joke> (It's like when someone says attorney generals... no, it's attorneys general...)

 

[Mudflat]

Those RPMs, 2800 at 65mph with 4.56 gears and 33" tires, are not correct for the 5-speed the OP has. With the 5-speed AX-15 the OP has, 4.56 would produce more like 2420 RPMs at 65 mph.

This is showing the RPMs with the transmission set for a the OP's AX-15 transmission, 4.56 axle ratio, and 33" tires which typically measure out more close 32.5" which is what I used for this calculation. This was produced with the gearing page at http://www.grimmjeeper.com/gears.html

View attachment 474064

Mine is an ‘06 so the transmission is the 6 speed manual.

 

[Jerry Bransford]

Mine is an ‘06 so the transmission is the 6 speed manual.

The rpms are still not going to be 2800 at 65 with 4.56 and 33" tires with the NSG370, its 6th gear is not that much higher at .84 vs .79 for a 5-speed like the AX-15. I used a 32.5" tire size for this calculation which is a fairly typical diameter for a 33" tire. The RPMs would be even lower if 33" is used for the tire size.