33's - Is this what I need?

[deadbeat son]

One more question - I’m going to need new carriers, right? What do I need to know about that? Lockers?

Yes, if you regear your current axles you'll need new carriers, which opens up a considerable menu in and of itself. You could use a simple stock replacement carrier for open differentials, a standard carrier with a lunchbox locker, a Truetrac or similar for a mechanical limited slip option, or a full case locker, either auto or selectable, such as a Detroit Locker, or ARB, respectively. If you're happy with 4.10 or 4.56 gears, although they're not the most ideal gearing for 33s, and you buy a set of complete axles from a 4cyl TJ, then you don't need to buy anything else unless you want/need locker(s).

 

[Austin O.]

Yes, if you regear your current axles you'll need new carriers, which opens up a considerable menu in and of itself. You could use a simple stock replacement carrier for open differentials, a standard carrier with a lunchbox locker, a Truetrac or similar for a mechanical limited slip option, or a full case locker, either auto or selectable, such as a Detroit Locker, or ARB, respectively. If you're happy with 4.10 or 4.56 gears, although they're not the most ideal gearing for 33s, and you buy a set of complete axles from a 4cyl TJ, then you don't need to buy anything else unless you want/need locker(s).

Thank you

 

[JMT]

@Austin O.

You’re thinking right. If you regear it’s also time to do lockers (or limited slip or a simple lunchbox). It’s cheaper doing it all at once rather than doing it twice.

 

[Austin O.]

@Austin O.

You’re thinking right. If you regear it’s also time to do lockers (or limited slip or a simple lunchbox). It’s cheaper doing it all at once rather than doing it twice.

Maybe the thinking was right, but thinking about my wallet is more important haha! I looked at it quite a bit - I think a powertrax no slip is what I would end up wanting. Thats easy enough to do in the future, right? (Once I have more to spend). I don’t think I’m willing to pay for anything more than a lunchbox style locker. I don’t wheel enough. Certainly not willing to spend that much as of now for a fancier locker. Any forum preference on open carriers?

 

[JMT]

Maybe the thinking was right, but thinking about my wallet is more important haha! I looked at it quite a bit - I think a powertrax no slip is what I would end up wanting. Thats easy enough to do in the future, right? (Once I have more to spend). I don’t think I’m willing to pay for anything more than a lunchbox style locker. I don’t wheel enough. Certainly not willing to spend that much as of now for a fancier locker. Any forum preference on open carriers?

Your thinking about your wallet? Get over that. Just kidding. Smart man.

I have a PowerTrax No-Slip in my front Dana 30. They are only good for a TJ in the front, and understand that when you shift into 4H the front is locked. They can be a little testy on snow and ice, but I've lived with mine for five winters and been ok. I just take turns slow. Every day driving it's invisible. Fault free since I installed it in 2018. It was relatively easy to install. Pull the carrier, remove the spider gears, and follow the instructions to install the PT No-Slip in it's place. You would do this after your gear change. You might ask the shop how much they would do it for since they will already be in there. It might be worth it. That's between you and your wallet. Cost me about $400 at the time. A front locker is a thing of beauty.

As far as your carrier as well as gears, I think check with the shop. Most of them will have a preferred gear brand. If you don't like the brand they want to use try calling another shop. If the shop provides the carrier and gears then they should warranty them. Ask these questions to make sure. Everyone here likes Revolution gears, so if that's what you want find a shop that will install them.

 

[TheBoogieman]

Doing THAT ^^^ is something I would regret.


This was one of the reasons I opted for 4.56. I am on the highway quite a bit and felt the slightly lower rpm would be better. Can't lie.. It seems perfect.
There is a long bridge that connects the mainland to the barrier island.. it's about two miles long and has a steady rise of about 1000 feet to the center. I can drive that grade in fifth at 65 with no lugging or other drama. Step on the gas it still has pull. Butt dyno confirms 4.56 was the correct call for me.

When doing any Jeep related mods, people need to do what's best for their needs. Most people just "parrot" the most expensive mods that aren't the best choice for everyone. When offroad, the best mod is driver skill. Not even the most expensive mods can make up for the lack of it. I learned this racing motocross for years. I have over 100 trophies packed in boxes and gathering dust in storage.

 

[Austin O.]

So I’ve contacted a couple regear shops today. Both have said 4.88s are way too steep for an ax-15, 4.0 and 33s. What’s with that? I was recommended 4.10s for 33s…

 

[jjvw]

So I’ve contacted a couple regear shops today. Both have said 4.88s are way too steep for an ax-15, 4.0 and 33s. What’s with that? I was recommended 4.10s for 33s…

They do not understand that your transmission has an overdrive. Make them use 4.88.

 

[MikekiM]

So I’ve contacted a couple regear shops today. Both have said 4.88s are way too steep for an ax-15, 4.0 and 33s. What’s with that? I was recommended 4.10s for 33s…

I missed where you said you are running the AX-15. Sorry if I misdirected you.

Still stand by 4.56ss for the NV-3550 with on a DD with 33's.

Carry on. All secure here in sector seven.

 

[jjvw]

I missed where you said you are running the AX-15. Sorry if I misdirected you.

Still stand by 4.56ss for the NV-3550 with on a DD with 33's.

Carry on. All secure here in sector seven.

Ax15 and nv3550 have the same OD. The answer is 4.88.

 

[Austin O.]

Alright… just odd that they both had the same reaction. And one of them talked on and on about his tj with a 4.0, ax15, 35s and 4.56 gears, said it was amazing. Said his boss has the same setup. According to this forum, it sounds like they’ve been missing out!

 

[JMT]

@Austin O.

It's seems to me that the main thing for you to do at this point is to understand the gear ratios in combination with your engine and transmission. We can go all day on here with one person citing their "experience" and another person citing the "numbers." I personally think the "numbers" are more important than someone's "experience" because people's "experiences" are all over the board, but the "numbers" don't change, but it's true that those that use the "numbers" also have "experience" to back up why they are citing a certain number (gear ratio) .

Something you can do is take your Jeep out on the road and see where your rpm's are currently at 70mph and how much power you have if you come up to a long or steep hill. What happens? Do you have to downshift from 5th to 4th? Or are you able to maintain your speed in 5th? If you can't hold your speed you're undergeared. Your rpm's are not high enough to keep speed. You're going to drop to 4th and then your rpm's are going to be well over 3,000rpm's. Is that really what you want? Or you can just let the Jeep slow down to 54mph to climb the hill. In what other vehicle is that really acceptable or the norm? Keep fooling around with speeds in a gear and when you find the rpm breaking point go to the gear calculator and find out what gear ratio would hold 70mph with your 33's. That will tell you the answer.

 

[jjvw]

Alright… just odd that they both had the same reaction. And one of them talked on and on about his tj with a 4.0, ax15, 35s and 4.56 gears, said it was amazing. Said his boss has the same setup. According to this forum, it sounds like they’ve been missing out!

This is common. And they have been missing out. They are geared much higher than the early TJ with the automatic. 75mph was about 3200 rpm, which is a higher rpm than the 3k at 75mph that I have been advocating for years.

Their jeeps are needlessly slow and sluggish.

 

[Austin O.]

@Austin O.

It's seems to me that the main thing for you to do at this point is to understand the gear ratios in combination with your engine and transmission. We can go all day on here with one person citing their "experience" and another person citing the "numbers." I personally think the "numbers" are more important than someone's "experience" because people's "experiences" are all over the board, but the "numbers" don't change, but it's true that those that use the "numbers" also have "experience" to back up why they are citing a certain number (gear ratio) .

Something you can do is take your Jeep out on the road and see where your rpm's are currently at 70mph and how much power you have if you come up to a long or steep hill. What happens? Do you have to downshift from 5th to 4th? Or are you able to maintain your speed in 5th? If you can't hold your speed you're undergeared. Your rpm's are not high enough to keep speed. You're going to drop to 4th and then your rpm's are going to be well over 3,000rpm's. Is that really what you want? Or you can just let the Jeep slow down to 54mph to climb the hill. In what other vehicle is that really acceptable or the norm? Keep fooling around with speeds in a gear and when you find the rpm breaking point go to the gear calculator and find out what gear ratio would hold 70mph with your 33's. That will tell you the answer.

I just did exactly this yesterday for all gears at a few different speeds. I then went to the gear calculator just as you said! From what I gathered, either 4.56s or 4.88s made sense to me and I am leaning towards 4.88s. (And this of course aligns with what you, as well as others on the forum have suggested). I’m not questioning that, was just wondering why gear shops were telling me differently.

I’m going to keep looking at used axles online and if a good option pops up for 4.56s or 4.88s, I’d seriously consider either. I’m also still considering getting a shop to do it, or even possibly looking at doing it myself when I have more time. Maybe I’ll buy used housings cheap and then do the install on there so I can take my time and then swap it into the tj. It’s certainly daunting, but I’m willing to try. I’m really just looking at all my options so I can make a good, informed, decision and I’m updating this thread as I do it. Thanks so much for your help!

 

[deadbeat son]

Alright… just odd that they both had the same reaction. And one of them talked on and on about his tj with a 4.0, ax15, 35s and 4.56 gears, said it was amazing. Said his boss has the same setup. According to this forum, it sounds like they’ve been missing out!

I had a shop insist that I needed 3.73s for 31s and they seemed to think I was ridiculous for wanting 4.56. After finding a different shop to do the work, I was elated with my 4.56/31 combination. I’m not sure why a shop would argue against something like that, but it’s likely because they have no experience whatsoever with it.

 

[BlueC]

I’m going to keep looking at used axles online

This shop is in Siler City, and they tend to keep some TJs around. When I was looking for a 44 a few years ago they had at least one axle set (35/30) with 4.56, and plenty of 4.10s

http://marshautoparts.com/about-marsh-auto-parts.html

 

[Austin O.]

This shop is in Siler City, and they tend to keep some TJs around. When I was looking for a 44 a few years ago they had at least one axle set (35/30) with 4.56, and plenty of 4.10s

http://marshautoparts.com/about-marsh-auto-parts.html

I’ll contact them. Thanks

 

[LONGJP2]

Alright… just odd that they both had the same reaction. And one of them talked on and on about his tj with a 4.0, ax15, 35s and 4.56 gears, said it was amazing.

Most that regear feel how much better it is and assume it's perfect.
What they don't realize is how much better it might have been.

Very few complain they regeared to low.
Even fewer admit they regeared too high.