Will I need to re-gear?

Jacob Mikesh

Jacob Mikesh

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May 25, 2018
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Alaska
I have a nearly bone stock 04 TJ unlimited. (Longer wheel base, 2 doors)

I bought it about 2 weeks ago from a used lot in fantastic condition. The only mod it has is the the original BFG wrangler 30" tires were replaced with BFG AT 31" tires. I want 33"s.

Ill probably need a small lift i dont wanna go big. I want a happy medium between daily driver and weekend wheeling. I have a dana 44/3.73 limited slip in the rear and dana 30/3.73 open diff front. I hope to one day add an e-locker in the rear but other than that will i need to regear for 33"s?

And any suggestion as to brands, lifts, tires, gears, ect would be greatly appriciated.
 
Old Man Emu will be recommended here pretty consistently.they have a great reputation here. More than a few memebers of this forum run their kit to include @Starrs. He runs 33’s and it looks great. Hopefully he will chime in.

https://www.dpgoffroad.com/product/old-man-emu-ultimate-tjlj-wrangler-kit/

I definitely advocate for a proper regear and lockers. Selectable lockers like e-lockers are perfect for the TJ/LJ owner looking for a road worthy yet trail ready rig.
 
If you have a Rubicon with factory gearing a person would be fine with 33s IMO. This is what I daily drive and I have the automatic transmission. I actually love my ride. I will add that I have never had 4.88s or 5.10s so I’m not positive what that rides like either. 33s and a rubi will be good to go. With you having 3.73s I would drive it and see if you absolutely hate it on accelerations and going up hills. You will know by the power you have or don’t have if you want to regear or not. Everybody is different when it comes to the gearing question.
 
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I’m just getting by with my 6-speed and 3.73 Gears. I plan to regear. So I can only imagine how bad it would be if I had an auto
 
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I dont have 33s yet. Just 31s. Im a novice and umder the impression that if you dont regear for bigger tires you could damage your drivetrain in someway. Could i leave the 3.73s and ride with 33s? I would only go up to 4.10s max. Im here to learn, i dont even know what kind of effect that would have. Ive just heard that damage could be done without proper gearing. I know gearing comes from the splines on the ring and pinion. But other than that dont know how a differential works or how it affects my tires. Sorry for my lack of knowlage but learning is the first step.
 
Even with the 31s it feels slow in the long run. On the first hit of the throttle its feels peppy though. I climbed up some small trails and decent rocks already with the 31s and had no issues with anything i tried.
 
33s really ought to have a minimum of 3.5" of total lift in order to maintain the stock amount of suspension up travel.

If I had the 42rle, I would absolutely want 5.13 gears with 33s. It just seems like a miserable transmission even from the factory. I drove my Jeep under-geared on the 5 speed for many years and never thought it was good. Now I am by some accounts over-geared and I think it is great.
 
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Jacob Mikesh said:
I dont have 33s yet. Just 31s. Im a novice and umder the impression that if you dont regear for bigger tires you could damage your drivetrain in someway.
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Your transmission doesn't like heat. Being undergeared creates heat.

Jacob Mikesh said:
Could i leave the 3.73s and ride with 33s?
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Most out there don't regear. That doesn't make it OK.

Jacob Mikesh said:
I would only go up to 4.10s max.
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If you are going to regear, then why stop short of the optimal gear ratio?

Jacob Mikesh said:
Im here to learn, i dont even know what kind of effect that would have. Ive just heard that damage could be done without proper gearing. I know gearing comes from the splines on the ring and pinion. But other than that dont know how a differential works or how it affects my tires. Sorry for my lack of knowlage but learning is the first step.
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Keep researching. This is fun stuff to learn and understand.

The biggest reason to regear is to raise the engine rpms back into the power band. At 75mph you want to be very near 3k rpm. Power, mileage and over-all driveability is why this is done.

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jjvw said:
33s really ought to have a minimum of 3.5" of total lift in order to maintain the stock amount of suspension up travel.

If I had the 42rle, I would absolutely want 5.13 gears with 33s. It just seems like a miserable transmission even from the factory. I drove my Jeep under-geared on the 5 speed for many years and never thought it was good. Now I am by some accounts over-geared and I think it is great.
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Again this is why I mentioned that gearing is gonna come down to personal preference. I have the 42rle 33” KM2s and factory Rubicon gearing....I daily drive my jeep and love my ride and have no gearing change in my future plans.
It’s the same as asking somebody “did that punch to the stomach hurt?” Some people may not feel it the same as others haha.
 
Jacob Mikesh said:
I dont have 33s yet. Just 31s. Im a novice and umder the impression that if you dont regear for bigger tires you could damage your drivetrain in someway. Could i leave the 3.73s and ride with 33s? I would only go up to 4.10s max. Im here to learn, i dont even know what kind of effect that would have. Ive just heard that damage could be done without proper gearing. I know gearing comes from the splines on the ring and pinion. But other than that dont know how a differential works or how it affects my tires. Sorry for my lack of knowlage but learning is the first step.
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3.73 to 4.10 wouldn't be worth the money. The 4 spd and 33's need 4.88 at a minimum, 5.13 is even better. Gearing has nothing to do with splines on the pinion. Gear ratio is determined by the number of teeth on the ring gear divided by the number of teeth on the pinion.

I have no personal experience with the 42rle but the constant up and downshifting when you install larger tires can cause excessive heat build up, which is a killer of any auto transmission.

Large tires and improper gearing can cause excess wear and tear as well as poor performance both on and off road. Lots of people do not re-gear simply because it is a significant expense. They talk themselves into running improper gearing saying "it works fine for me." Look at it this way, Jeep installed 3.73's to run with a 29x8.50 tire. It is ridiculous to think lifting it and adding a 33x12.50 tire will perform properly. Installing a 33 on the 3.73 is like the stock tires with 3.07. And I don't think you will find anyone that feels the 3.07 is appropriate in a Jeep.
 
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Starrs said:
Again this is why I mentioned that gearing is gonna come down to personal preference. I have the 42rle 33” KM2s and factory Rubicon gearing....I daily drive my jeep and love my ride and have no gearing change in my future plans.
It’s the same as asking somebody “did that punch to the stomach hurt?” Some people may not feel it the same as others haha.
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Running gears appropriate for your tire size will always feel much better than a punch to the stomach. :)
 
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All great information. I really do appriciate becoming a member of the jeep community. All concidered i will eventually be getting the lift, 33s, and be regearing. I wanna do thing right. im not gonna run my TJ into the ground. And definatly not get punched in the stomach haha. Its just a matter of what gears will fit into the Dana 44 and Dana 30, what gear i need to properly run 33s, and wether or not i can regear in my own garage or if its to complicated.
 
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Rob5589 said:
3.73 to 4.10 wouldn't be worth the money. The 4 spd and 33's need 4.88 at a minimum, 5.13 is even better. Gearing has nothing to do with splines on the pinion. Gear ratio is determined by the number of teeth on the ring gear divided by the number of teeth on the pinion.

I have no personal experience with the 42rle but the constant up and downshifting when you install larger tires can cause excessive heat build up, which is a killer of any auto transmission.

Large tires and improper gearing can cause excess wear and tear as well as poor performance both on and off road. Lots of people do not re-gear simply because it is a significant expense. They talk themselves into running improper gearing saying "it works fine for me." Look at it this way, Jeep installed 3.73's to run with a 29x8.50 tire. It is ridiculous to think lifting it and adding a 33x12.50 tire will perform properly. Installing a 33 on the 3.73 is like the stock tires with 3.07. And I don't think you will find anyone that feels the 3.07 is appropriate in a Jeep.
Click to expand...
Jacob Mikesh said:
I have a nearly bone stock 04 TJ unlimited. (Longer wheel base, 2 doors)

I bought it about 2 weeks ago from a used lot in fantastic condition. The only mod it has is the the original BFG wrangler 30" tires were replaced with BFG AT 31" tires. I want 33"s.

Ill probably need a small lift i dont wanna go big. I want a happy medium between daily driver and weekend wheeling. I have a dana 44/3.73 limited slip in the rear and dana 30/3.73 open diff front. I hope to one day add an e-locker in the rear but other than that will i need to regear for 33"s?

And any suggestion as to brands, lifts, tires, gears, ect would be greatly appriciated.
Click to expand...



Let me slow this thing down for a second...moving from 31” factory to 33” does NOT require rehearing. And please don’t listen to the folks implying that the deeper the gear the better, you’ll only be bouncing off the rev limiter if you follow some advice here. When you move to 35+ AND off-roading then you’ll want to get gears done and bring everything back into the power and designed. But from your description, you’re not there yet. Invest in a long arm lift instead, it will grow with you as does your experience
 
Jacob Mikesh said:
All great information. I really do appreciate becoming a member of the jeep community. All considered i will eventually be getting the lift, 33s, and be re-gearing. I wanna do thing right. I'm not gonna run my TJ into the ground. And defiantly not get punched in the stomach haha. Its just a matter of what gears will fit into the Dana 44 and Dana 30, what gear i need to properly run 33s, and whether or not i can re-gear in my own garage or if its to complicated.
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With the TJ 30, 5.13 is the lowest you can run. Differential set up is not for the inexperienced.
 
Heisenberg said:
Let me slow this thing down for a second...moving from 31” factory to 33” does NOT require rehearing. And please don’t listen to the folks implying that the deeper the gear the better, you’ll only be bouncing off the rev limiter if you follow some advice here. When you move to 35+ AND off-roading then you’ll want to get gears done and bring everything back into the power and designed. But from your description, you’re not there yet. Invest in a long arm lift instead, it will grow with you as does your experience
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:meparto: Wait, you were serious? Do some calculations before talking about "bouncing off the rev limiter." A long arm is not an investment, it is a waste of hard earned dollars. A Savvy mid arm, now you are talking.
 
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Starrs said:
If you have a Rubicon with factory gearing a person would be fine with 33s IMO. This is what I daily drive and I have the automatic transmission. I actually love my ride. I will add that I have never had 4.88s or 5.10s so I’m not positive what that rides like either. 33s and a rubi will be good to go. With you having 3.73s I would drive it and see if you absolutely hate it on accelerations and going up hills. You will know by the power you have or don’t have if you want to regear or not. Everybody is different when it comes to the gearing question.
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I have the same set up and completely agree with you. No need to re-gear.


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