What should I re-gear my TJ to?

[Bbrayden85]

I know there are tons of forums on regearing but i just want to figure out whats best for me and my setup. I have a 1997 jeep wrangler se, it has dana 30 in front and dana 35 in back. I am rolling on 31” tires. I plan to do mostly commuting in the jeep, with occasional camping trip in the mountains. It would be mostly highway driving. I also plan to stay on 31s. What gears am i on right now assuming its stock, and what gears should i go to to get the best fuel economy, accurate speedometer, and able to keep up with speedy traffic. Also what would be a good price and at what point am I getting ripped off? Also has anyone had any experience with any shops in the yakima area. Thanks!

 

[PNW Lj]

What gears am i on right now assuming its stock

You can do this a few different ways (p.s. should be like a 4.10 if your a manual 4 cyl)

1) See if you can get your build sheet, might not be able to as it may only work for 98 and up
https://wranglertjforum.com/threads/how-can-i-find-the-build-sheet-for-my-jeep-wrangler-tj.3838/
2) roll under it and see if the tag is still on it to identify

3) jack it up, pull the cover and read the gear

4) jack it up, hold one tire and spin the other, count how many times the pinion goes around for one revolution of the tire

what gears should i go to to get the best fuel economy, accurate speedometer, and able to keep up with speedy traffic.

Do the math (people will argue with this, but this is the math)
(New tire size/Old tire size)* current gear ratio = new ratio

factory tire size on your jeep should have been like a 215 or 225/75r15, so 27.5ish, and if we assume you have 4.10s should look like this

(31/27.5)*4.10= 4.62, so a 4.56 or a 4.88 would be a good choice (remember this is an example, check what gears you have first, some early 4cyl got 3.73, and some magic ones had factory 4.56)

Also what would be a good price and at what point am I getting ripped off? Also has anyone had any experience with any shops in the yakima area. Thanks!

Not gunna give you dollars and cents here, because there's to many variables, but at least here's guide line.

https://www.quadratec.com/p/yukon-g...ERBAkLkwwjFhQatJIBSkZbsH4ZRX8EAhoCFhEQAvD_BwE
that is an example of most of what you would need, one thing to note here is that if you are for whatever reason have like a 3.55, you will need new carriers as well.

assume that the shop will be paying near that price for the parts, and obviously aren't just going to trade dollars with you, they need to mark it up, probably in the range of 25-50%

labor will range (this is for both axles) from about 5 hours on the low end to 10 on the very high end, last I heard rates in Yakima were around 100 an hour, may be more.

add tax, and that will give you an idea

Hope that helps

 

[Bbrayden85]

Tha

You can do this a few different ways (p.s. should be like a 4.10 if your a manual 4 cyl)

1) See if you can get your build sheet, might not be able to as it may only work for 98 and up
https://wranglertjforum.com/threads/how-can-i-find-the-build-sheet-for-my-jeep-wrangler-tj.3838/
2) roll under it and see if the tag is still on it to identify

3) jack it up, pull the cover and read the gear

4) jack it up, hold one tire and spin the other, count how many times the pinion goes around for one revolution of the tire


Do the math (people will argue with this, but this is the math)
(New tire size/Old tire size)* current gear ratio = new ratio

factory tire size on your jeep should have been like a 215 or 225/75r15, so 27.5ish, and if we assume you have 4.10s should look like this

(31/27.5)*4.10= 4.62, so a 4.56 or a 4.88 would be a good choice (remember this is an example, check what gears you have first, some early 4cyl got 3.73, and some magic ones had factory 4.56)


Not gunna give you dollars and cents here, because there's to many variables, but at least here's guide line.

https://www.quadratec.com/p/yukon-g...ERBAkLkwwjFhQatJIBSkZbsH4ZRX8EAhoCFhEQAvD_BwE
that is an example of most of what you would need, one thing to note here is that if you are for whatever reason have like a 3.55, you will need new carriers as well.

assume that the shop will be paying near that price for the parts, and obviously aren't just going to trade dollars with you, they need to mark it up, probably in the range of 25-50%

labor will range (this is for both axles) from about 5 hours on the low end to 10 on the very high end, last I heard rates in Yakima were around 100 an hour, may be more.

add tax, and that will give you an idea

Hope that helps

that is helpful thank you. The build sheet says my jeep came with 4.11 gears. Would 4.56 make my speedometer accurate? Also i dont want to rev to the moon to go highway speeds but i want to be able to go highway speeds. If that makes sense. Someone on another forum said 4.56 is perfect for 31s

 

[Bbrayden85]

It also came factory with 205 75R 15s

 

[PNW Lj]

that is helpful thank you. The build sheet says my jeep came with 4.11 gears. Would 4.56 make my speedometer accurate? Also i dont want to rev to the moon to go highway speeds but i want to be able to go highway speeds. If that makes sense. Someone on another forum said 4.56 is perfect for 31s

That's why you use the calculation, your jeep was built with the original tire size in mind, thus the factory set it up the way they did. when you moved to a larger size tire, you in effect made your gear ratio higher, as the jeep is now moving further with every rotation.

Example: factory 205/75R15 =27.11in, making the distance that tire travels (the circumference) with each revolution 85.17 in (2(pi)r)
the new tire is a 31in, making the distance that tire travels 97.39in with each revolution, thus when we put bigger tire on the speedometer reads slow. the jeep is now moving roughly 14.3% (pay attention to this number it will come up again) faster than it was stock. (and we get that number by taking the new distance - the old distance and dividing it by the old distance, then multiplying by 100)

So how do we get it back to the way it was? we need to lower the gear ratio (obviously), thus we come back to the original calculation (new tire/old tire)*old ratio= new ratio

if we start with the first piece
new tire/old tire, we will get the quotient that we need to find the new gearing (the percent the tire has changed)
Example: lets say we were going to a smaller tire, 27/31= 0.87, this number tells us that the new ratio needs to 87% the size of the old Ratio. this make sense because the new tire goes a smaller distance with each revolution, thus the gear ratio would need to be higher.

with your jeep we are going to a bigger tire, 31/27.11=1.143, this number tells us that the new ratio needs to be 114% the size of the old ratio ( The new ratio Is 14.3% lower), we are back to the number we had before.

Now the second piece
multiply this number by your old ratio and you will have a ratio that is 14.3% lower, there by matching what the jeep was when it was stock

1.143*4.11=4.6997, so in this case as that gear set don't exist, shoot for the next closest this 4.56 will be a bit high, 4.88 will be a bit low. The choice is yours, and I hope this make sense

 

[Rubicon88]

4.88 is your target gear IMO

Trust me.
You have 4.10 now...going to a 4.56 is NOT enough of a change when you factor in the added weight of the larger tire and increased rolling resistance.
You can use all the age old formulas to death but they don't factor in added weight and rolling resistance of a tire.

You say you'll only go with 31's...ok...but let me tell you (I sell tires every day) rolling resistance and weight between tread is a very real thing. Especially when dealing with the little 2.5 engine. Low power turns into NO power real quick.

4.88's will not only bring that back to stock performance but the little bit extra RPM you'll have will help combat the added tire weight and resistance on hills.

Good luck.

P.s.

Changing gears if not doing it yourself is not cheap.
You definitely want to do it once with the right ratio. In other words don't be left wanting or wishing you had more gear.

 

[PNW Lj]

4.88 is your target gear IMO

You say you'll only go with 31's...ok...but let me tell you (I sell tires every day) rolling resistance and weight between tread is a very real thing. Especially when dealing with the little 2.5 engine. Low power turns into NO power real quick.

4.88's will not only bring that back to stock performance but the little bit extra RPM you'll have will help combat the added tire weight and resistance on hills.

Good luck.

^ This is sound advise, in the off-road world as an in general statement, it's almost always better to lean lower than higher. I want to give you the tools and understanding to make your own decisions, but if I was in your shoes, I too would go 4.88's.

You say you'll only go with 31's...ok...but let me tell you (I sell tires every day) rolling resistance and weight between tread is a very real thing. Especially when dealing with the little 2.5 engine. Low power turns into NO power real quick.

^ This is very true, not to mention that even the same size tires from different brands may actually be different sizes (and graphicly different weights too). as an example, I currently run a 265/75r16, plug that in to google and it will tell you that's a 31.6" tire, go actually look at manufactures specs and you will see that the size varies form 31.4 - 32.01 (the rim width you are mounting on will also change this height). Doesn't seem like that big a deal, but if we run the calculation again for a 32" tire, your new ratio becomes 4.85!

P.s.

Changing gears if not doing it yourself is not cheap.
You definitely want to do it once with the right ratio. In other words don't be left wanting or wishing you had more gear.

^ The man Speaks The Truth

 

[AndyG]

Changing gears if not doing it yourself is not cheap.

Well said, as well as all the post.

I was thinking as I read it ....don’t regear it at shop cost if it’s an SE, the cost will nearly get you into a 4.0 that can likely handle 31” tires. Don’t trade for rusted junk , let your dad or an uncle help you trade or sell and buy.

Just a suggestion.

another thought ....what is more expensive than a shop regear? My do it yourself one I ruined. It was soooooo bad .

 

[Rubicon88]

Well said, as well as all the post.

I was thinking as I read it ....don’t regear it at shop cost if it’s an SE, the cost will nearly get you into a 4.0 that can likely handle 31” tires. Don’t trade for rusted junk , let your dad or an uncle help you trade or sell and buy.

Just a suggestion.

another thought ....what is more expensive than a shop regear? My do it yourself one I ruined. It was soooooo bad .

Agreed.
The best way to do it is practice on one but most don't have one available for that purpose or willing/able to shelf their Jeep for practice time on their own.

Even using same components just getting in there and taking apart and putting back together does wonders in the learning process. Understanding how it all works....etc...learning backlash, preload and exactly why and what it all means. But most don't have the resources to do that.

 

[PNW Lj]

Agreed.
The best way to do it is practice on one but most don't have one available for that purpose or willing/able to shelf their Jeep for practice time on their own.

Even using same components just getting in there and taking apart and putting back together does wonders in the learning process. Understanding how it all works....etc...learning backlash, preload and exactly why and what it all means. But most don't have the resources to do that.

Another good option may be to wait for someone to be upgrading, and buy their take offs. 4.88's are a common swap gear, and you may be able to buy a set of used axles for less than the cost of regearing your own. Plus you may be able to get some that already have goodies like alloy axles, lockers and trusses already installed

 

[Bbrayden85]

Another good option may be to wait for someone to be upgrading, and buy their take offs. 4.88's are a common swap gear, and you may be able to buy a set of used axles for less than the cost of regearing your own. Plus you may be able to get some that already have goodies like alloy axles, lockers and trusses already installed

I was looking at remanufactured ones built with 4.88. But thats just way too much money. I will be waiting, but id really like to be able to daily this because my xj is on its way out

 

[Rubicon88]

Another good option may be to wait for someone to be upgrading, and buy their take offs. 4.88's are a common swap gear, and you may be able to buy a set of used axles for less than the cost of regearing your own. Plus you may be able to get some that already have goodies like alloy axles, lockers and trusses already installed

Perhaps but most of those guys already have 17 people yelling at their ear if they ever upgrade again I want those axles...you know the story.

Exactly why a lot of good Jeeps never hit a dealer's lot or classifieds. They know someone who knows someone that jumps on it the moment word is out for sale.
Same reason Jeep Wranglers are the #1 scarce item at the bone yard. A lot of "real Jeeps" that could be salvage candidates get rebuilt over and over and never go to the bone yard.

Good mud tires...same thing. Unless the owner is too proud of his set and wants too damn much they usually are in a clique that has someone who wants them immediately. Find a set of Boggers with decent tread left for a reasonable price listed in a classified. LOL. They never get there. Already sold.

 

[jimstj]

My jeep is in the shop right now getting re-geared. I spent a lot of time thinking this through. I have some similarities and differences to your rig so i will share my thinking as to why I chose my target ratio.

2002 model x 5spd 4.0L pushing 3.07 gears with a dana 30/35 rolling 31s. I use this more as an over-lander rig, and really do not crawl. I spent a lot of time with the calculator at http://www.grimmjeeper.com/gears.html and considered my driving habits and what I wanted to accomplish.

what I did not like with old setup:
No first gear performance, and an almost useless 5th gear.
Any kind of hill required me to drop down to 3rd
acceleration left me wanting
I do not feel comfortable towing much with those tall gears
when off road, I felt like any obstacles required me to slip the clutch too much or always go into 4L

I decided to go to a 4.56 ratio and will keep my 31s for the time being. Replacement tires will be 33s 12.5. I also added a Truetrac LSD.
When you look at the calculator the difference between the tire sizes only means I will spin a bit higher down the highway, but will still be acceptable on the 31s. I tend to not be in a hurry when jeeping down the hwy. The calculator will show you speeds at a given RPM and RPMs at a given speed.

I believe this setup will address all of the things above I was wanting to improve. I am not sure about fuel economy, but normally I was running at RPMs too low which does not help fuel economy. I am hoping I will be running more in the sweet spot of engine performance and that will result in better fuel economy, but none of my decisions considered fuel economy a major factor nor did Speedo accuracy.

As for price I am not sure how LA compares to your location, but usually we are on the high side. So total parts - gears for the 30 and 35, LSD for the 35, replacement carrier for the 30. All in at a reputable shop for $2,200

And I must say, I cannot wait to get in it with the new gears!!

 

[Bbrayden85]

anyone recommend rough country gears? I really like the brand and everything i have bought has been very high quality. Or is there a better value brand?

 

[Jerry Bransford]

Rough Country sources their gears from lowest bidder, they don't make them. Luck of the draw on who makes them. Revolution Gear & Axle is probably the very best aftermarket, they source their gears solely from Circle K in S. Korea who is considered the best aftermarket manufacturer of gears. Genuine Gear, Motive, Yukon, etc. are all good providers too. My personal choice was RGA.

 

[ColoJeep]

Another possible option is Sierra Gear, I have used them in my re gear in 2013 with zero issues.

They also make OEM and Chromolly Axles.

 

[Vasq]

anyone recommend rough country gears? I really like the brand and everything i have bought has been very high quality. Or is there a better value brand?

Are you in Naches, as in WA?

 

[Bbrayden85]

Are you in Naches, as in WA?

Yes

 

[Vasq]

Yes

I'd look at MULE in Issaquah, they use Nitro Gears and have a really good reputation.