Why should I regear?

[Zandcwhite]

The one factor that can come into play is the lockup feature of the torque converter.

Modern transmissions with good computer control are better than they used to be. But if you have a big mismatch like 3.45 gears and 35s, you may end up with the computer never locking up the torque converter. That reduces efficiency and generates extra heat. If your cooling system can handle it, it's not a huge deal. But it's less than ideal.

If I read correctly the torque converter is always locked up above 3rd gear. If that's the case for the most part I don't think it would be an issue. With 3.45s and 35s I'd likely look to regear or find a set of Rubicon take offs and gain gears and lockers and wider axles and bigger brakes in the process. The extremes are where I'm all for a regear, but I susp caution against going too far the other direction. Personally I felt the factory xr 4.56s and 35s was a bit over geared running freeway speeds. Having jumped all the way to 5.38s on 38s in our 2019 I can say that was the worst all around gearing of anything we've run with this 8 speed. Even 4.10s and 38s was better.

Sponsored

 

[grimmjeeper]

If I read correctly the torque converter is always locked up above 3rd gear. If that's the case for the most part I don't think it would be an issue. With 3.45s and 35s I'd likely look to regear or find a set of Rubicon take offs and gain gears and lockers and wider axles and bigger brakes in the process. The extremes are where I'm all for a regear, but I susp caution against going too far the other direction. Personally I felt the factory xr 4.56s and 35s was a bit over geared running freeway speeds. Having jumped all the way to 5.38s on 38s in our 2019 I can say that was the worst all around gearing of anything we've run with this 8 speed. Even 4.10s and 38s was better.

Yeah, I haven't kept up with exact tuning of the transmission and the lockup behavior beyond knowing they're a lot better than they used to be.

Last time I really dealt with a lockup in detail was when I swapped in a 700R4 with its analog system. I had to swap out the brake switch with the extra plug so it would cut power to the solenoid when you hit the brakes. I also fabbed in the vacuum switch that would cut the power when the engine started to load up, before it needed to downshift. Worked pretty well. But only in 4th (top) gear.

 

[mgroeger]

So I know there are several threads on regearing, but they mainly centered on what ratio to go with. I want to know the why’s. 2018 JLU Sport S, 3.6, auto, 35x12.5x17 MT Baja Boss AT, 2.5-3” lift(already installed when purchased used).

Why should I spend ~$3000 to regear just because I have 35s and a lift?
Is it just about seeing 8th gear again?
mpg improvement? How much?

Or is there a mechanical/performance reason?

I am not a mechanic nor pretend to be one, so please don’t get to technical.

You should never spend $3k on a re-gear. They run about $2k.

 

[Zandcwhite]

You should never spend $3k on a re-gear. They run about $2k.

Unless you're in CA where labor rates are astronomical, then they run about $3k.

 

[mgroeger]

Unless you're in CA where labor rates are astronomical, then they run about $3k.

Reason 3,729 not to live in CA

 

[Zandcwhite]

Reason 3,729 not to live in CA

As a union electrician there's no better place to live. Journeymen in Charlotte (the highest paid local in NC) make $32.83/hr and only get an additional $3.60/hr in their pension. Our JWs make $91.03/hr and $36/hr in the pensions. That difference pays for a whole lot of overpriced regears... and I could run the Rubicon every weekend in the summer. I won't be here when I retire but I sure as hell wouldn't be in this profession elsewhere for 1/3 the wages and 1/10th the retirement.

 

[bllprk]

Going back to your original question. Why should you re-gear?

The short answer is: To get the right balance of functionality and experience.

Long Answer:
A drivetrain is comprised of the engine (power), transmission, transfer case, axle gears, and tire diameter. All of these work together to provide the ability for a vehicle to move a range of speeds.

The goal when designing a system is to provide a certain driving functionality and experience.

Functionality = Does the jeep move?

Experience = You can design the system for max speed, or best gas mileage or best acceleration or best towing ect… (experience)

Engineers pick what they feel is the right combination and then design the system to find what they feel is the right balance between functionality and experience.

Gearing (in a transmission, TC, or axles) exchanges speed and torque. Want more speed? You get less torque. Need more torque? You get less speed.

The larger tires, will increase your top speed. (They travel a longer distance per revolution than the smaller tires.) But because you gain more speed, you lose torque.

So why re-gear?

1. (Feeling / Performance) The loss of torque due to larger tires can make the jeep feel sluggish from a stop. The jeep can still function, but with a lower rate of acceleration, so its functionally still ok, but not as fun to drive (experience decrease). Re-Gearing can bring back the fun or peppy feeling of accelerating from a stop.

2. (Gas Mileage) Because the larger tires increase the overall speed of the drivetrain, every gear in the transmission will produce more speed, so you no longer need the high gears (6,7,8) because the system has the speed it needs. If you don't use all the gears in the transmission, you are loosing the max efficiency of the transmission, creating a loss is gas mileage.

3. (Wear and Tear) Engines have a range of speed (RPM) and torque. When RPM goes up on a gas engine, torque goes up as well. Often, to compensate for the lack of torque due to larger tires, you need to rev the engine higher to generate that extra torque. Higher RPM means the engine is running harder, and could contribute to accelerated wear.

All this said.. as long as the jeep can function (for what you need), and you are ok with the experience, there is no huge reason to re-gear. Maybe its easier on the engine, maybe it could get better gas mileage, but if you are happy with how it drives, then you will be ok.

One last note: If you re-gear, you get to design the drivetrain to behave how you want it to behave. Make it most like stock. Yes you can do that. Make it accelerate faster? Yes you can do that. Make it a better rock-crawler. Yes...

Good luck!

 

[mgroeger]

As a union electrician there's no better place to live. Journeymen in Charlotte (the highest paid local in NC) make $32.83/hr and only get an additional $3.60/hr in their pension. Our JWs make $91.03/hr and $36/hr in the pensions. That difference pays for a whole lot of overpriced regears... and I could run the Rubicon every weekend in the summer. I won't be here when I retire but I sure as hell wouldn't be in this profession elsewhere for 1/3 the wages and 1/10th the retirement.

But what about other factors of living in CA like the cost of housing, cost of gas, groceries, taxes, etc... Factor all of that in and I'm sure those rates start to come a lot closer to each other.

 

[entropy]

As a union electrician there's no better place to live. Journeymen in Charlotte (the highest paid local in NC) make $32.83/hr and only get an additional $3.60/hr in their pension. Our JWs make $91.03/hr and $36/hr in the pensions. That difference pays for a whole lot of overpriced regears... and I could run the Rubicon every weekend in the summer. I won't be here when I retire but I sure as hell wouldn't be in this profession elsewhere for 1/3 the wages and 1/10th the retirement.

I am gonna start flying electricians from NC lol.

 

[Necro]

 

[entropy]

But what about other factors of living in CA like the cost of housing, cost of gas, groceries, taxes, etc... Factor all of that in and I'm sure those rates start to come a lot closer to each other.

I used to live in Vermont, countryside not the expensive part. It was pretty cheap. We moved to California about 7 years ago. LA area, very expensive. We are way richer now than we were in Vermont overall. Smaller house, smaller lot, but everything is pristine and high quality. Even with the high cost of labor, gas, housing, etc...

We couldn't make nearly as much money as we make here in NC.

 

[Zandcwhite]

But what about other factors of living in CA like the cost of housing, cost of gas, groceries, taxes, etc... Factor all of that in and I'm sure those rates start to come a lot closer to each other.

I've lived a few places traveling for work around the country and it's still not even close. Groceries are just as expensive everywhere. Gas being a dollar cheaper a gallon certainly does little when you're 1st hour of the day buys an entire tank of gas. Fortunately I bought my house when I was still an apprentice 23 years ago so we are well insulated even there. I can tell you by the number of traveler's I've had on my crew's over the decades that are still supporting their families back home while being out here for work it absolutely doesn't add up. I was down in the Phoenix area for work last year, their average home price is now pushing $600k... and their wages are nearly identical to Charlotte. As a tradesman it doesn't make sense to live/work anywhere else. And with the wages comes better treatment by the employers just by human nature. You're going to treat a guy worth $91/hr better than a guy worth $32 even if it's unintentional. And you won't find better working weather year round. There's a reason why we get guys from all over out here all the time and it's not the cost of living.

 

[entropy]

What is this showing? high RPMs at a low speed? High gearing (lower number) should allow for higher speeds....

Or are you trying to illustrate the opposite?

 

[Zandcwhite]

I am gonna start flying electricians from NC lol.

That's the beauty of the trades, they might come from NC... but they'll make our wages when they do.

 

[mgroeger]

I used to live in Vermont, countryside not the expensive part. It was pretty cheap. We moved to California about 7 years ago. LA area, very expensive. We are way richer now than we were in Vermont overall. Smaller house, smaller lot, but everything is pristine and high quality. Even with the high cost of labor, gas, housing, etc...

We couldn't make nearly as much money as we make here in NC.

So again... you are not comparing apples to apples... "smaller house, smaller lot". So if you were to actually buy the same size house and land I would guess you would not be "way richer".

Sponsored