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Old 04-10-2013, 08:43 AM   #1
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3.73 gears?

So I currently have the stock gears in my 2006 wrangler, and I have talked with my dad about having his friend re-gear it to 3.73 for me. My dad is concerned that the gas mileage will be a lot worse if I do decide to re-gear. I don't do much highway driving, mostly around town going to school and back. Any input on this? Thanks guys.

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Old 04-10-2013, 09:07 AM   #2
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I have the 3.73s in my jk wrangler and I still average 14 15 miles to the gallon with 32s on it

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Old 04-10-2013, 09:10 AM   #3
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I have the 3.73s in my jk wrangler and I still average 14 15 miles to the gallon with 32s on it
Is yours a manual trans? I've got the 6 speed manual running 33's
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Old 04-10-2013, 09:12 AM   #4
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Within limits, if you've got upsized tires, deeper gears often improve your gas mileage by increasing the engine's mechanical efficiency over the tires. You ride the skinny pedal less, and lug the engine less.

Tire size, gearing, fuel efficiency, and driving habits and style are always a balancing act. Overweighing one usually impacts the others.

You've increased tire size, so chances are you're no longer as efficient as you were previously. If you rebalance appropriately, you may find the jeep performs better all around.
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Old 04-10-2013, 09:42 AM   #5
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Originally Posted by mang318 View Post
So I currently have the stock gears in my 2006 wrangler, and I have talked with my dad about having his friend re-gear it to 3.73 for me. My dad is concerned that the gas mileage will be a lot worse if I do decide to re-gear. I don't do much highway driving, mostly around town going to school and back. Any input on this? Thanks guys.
-Someone else can comment but the are recommended "optimal" gear ratios based on engine/trans/tire. 3.73 is not it for 33.

- What gear do you have now? You also have to look at cost vs benefit. The jump to 3.73 probably is not very big over what you have now. The cost of regearing to only 3.73 really is not worth it.

- City mileage will improve from the regear. With the gear ratio you have now, your engine is working a lot harder getting the vehicle moving with stop/go driving. (Note you will not recoup the cost of regaering in gas savings)
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Old 04-10-2013, 09:49 AM   #6
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Originally Posted by mang318 View Post
So I currently have the stock gears in my 2006 wrangler, and I have talked with my dad about having his friend re-gear it to 3.73 for me. My dad is concerned that the gas mileage will be a lot worse if I do decide to re-gear. I don't do much highway driving, mostly around town going to school and back. Any input on this? Thanks guys.
For 33" tires and your 5-speed, 4.10 would be the more optimal gear ratio that would likely improve, not decrease, your MPG. 3.73 is what the factory installed for smaller 30" tires which was an optimal ratio/tire size combination which won't be optimal for your 33" tires. To get the same engine rpms the factory combination produced, you need the 4.10 axle ratio.

Lower engine rpms don't necessarily improve mpg, there is a point where lower engine rpms harm the mpg by causing the engine to run inefficiently.
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Old 04-10-2013, 11:26 AM   #7
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For 33" tires and your 5-speed, 4.10 would be the more optimal gear ratio that would likely improve, not decrease, your MPG. 3.73 is what the factory installed for smaller 30" tires which was an optimal ratio/tire size combination which won't be optimal for your 33" tires. To get the same engine rpms the factory combination produced, you need the 4.10 axle ratio.

Lower engine rpms don't necessarily improve mpg, there is a point where lower engine rpms harm the mpg by causing the engine to run inefficiently.
But would 4.10's decrease gas mileage? Would 3.73's decrease it? I'm not worried about costs since we wouldn't be taking it to a shop anyway, so I wont be paying for labor. I'm just concerned if there would be a major difference in fuel economy. I get about 15 MPG now and if I could re-gear and keep it there that would be great.
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Old 04-10-2013, 11:48 AM   #8
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MTH, Jerry and I addressed mileage and impact. There is not going to be a major difference.
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Old 04-10-2013, 11:48 AM   #9
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But would 4.10's decrease gas mileage?
Re-read my response to you again please, I already very specifically answered that question for you.
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Old 04-10-2013, 11:51 AM   #10
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But would 4.10's decrease gas mileage? Would 3.73's decrease it? I'm not worried about costs since we wouldn't be taking it to a shop anyway, so I wont be paying for labor. I'm just concerned if there would be a major difference in fuel economy. I get about 15 MPG now and if I could re-gear and keep it there that would be great.
There's no magic formula anyone is going to have for you.

Your mpgs depend on driving style, tire size and choice, gearing, etc. We can't come on here and say that if you get 3.73 gears, your mpgs will go up exactly X mpgs, and if you get 4.10s it will go down exactly Y mpgs, etc.

The best way to consider it is exactly as Jerry said: "Lower engine rpms don't necessarily improve mpg, there is a point where lower engine rpms harm the mpg by causing the engine to run inefficiently."

In other words, just because your going to deeper (numerically higher) gears doesn't necessarily mean your mpgs are going to go down. You may find a mpg improvement at 4.10s.

The bottom line is that right now, you're running tires that are oversized for the gearing that you have with respect to your engine and transmission. That is inefficient. Inefficiency generally lowers mpgs. A regear that maximizes efficiency will therefore probably INCREASE your mpgs.

How much? Not sure. Will mpgs be better on the highway as well as around town? Don't know. Can we be absolutely positive that 4.10s will improve your mileage? Of course not . . . but it probably will.
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Old 04-10-2013, 11:54 AM   #11
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I apologize, I was spacing out. I could be wrong but I believe my stock gears are 3.07 (going to check to make sure when I get home). Would 4.10's kill my gas mileage on the highway? I usually don't do much highway driving but I will be going on trips to offroad parks this summer like the cliffs and badlands. Sorry I know I have alot of questions but I'm new to this whole regearing idea
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Old 04-10-2013, 11:58 AM   #12
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I apologize, I was spacing out. ...Would 4.10's kill my gas mileage on the highway?
Are you not reading for comprehension our many responses to that question?
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Old 04-10-2013, 12:00 PM   #13
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I apologize, I was spacing out. I could be wrong but I believe my stock gears are 3.07 (going to check to make sure when I get home). Would 4.10's kill my gas mileage on the highway? I usually don't do much highway driving but I will be going on trips to offroad parks this summer like the cliffs and badlands. Sorry I know I have alot of questions but I'm new to this whole regearing idea
I think you're still spacing out. Read the responses above--this has been answered as best as it can.

And since you're really only considering 3.73 or 4.10 ratios, perhaps another approach is warranted . . . I believe TJ Rubicons came stock with 4.10 gears and smaller tires than you have right now. Do they have terrible gas mileage versus your TJ? Why would an auto manufacturer offer an optional STOCK gear ratio that is a terrible choice and "kills" mileage?

You'll be fine with 4.10s. It'll be better all around than either 3.07s or 3.73s for your 33s. Overall mpg impact will probably be neutral, or perhaps even a small improvement. Though it could conceivable go down a bit . . . but not by much.

That's as specific an answer as I believe is possible.
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Old 04-10-2013, 12:03 PM   #14
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I think you're still spacing out. Read the responses above--this has been answered as best as it can.

And since you're really only considering 3.73 or 4.10 ratios, perhaps another approach is warranted . . . Rubicons come stock with 4.10 gears. Do they have terrible gas mileage versus your TJ?
That helps alot thanks. Not so confused anymore.
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Old 04-10-2013, 12:05 PM   #15
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If I did decide to regear and go with 4.10 gears, any other suggestions you guys have? Or anything to keep in consideration?
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Old 04-10-2013, 12:06 PM   #16
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That helps alot thanks. Not so confused anymore.
I predict much happiness if you go with 4.10s.
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Old 04-10-2013, 12:13 PM   #17
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I predict much happiness if you go with 4.10s.
I love my jeep now! If I put 4.10's in it then it would be even more awesome!
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Old 04-10-2013, 12:50 PM   #18
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If I did decide to regear and go with 4.10 gears, any other suggestions you guys have? Or anything to keep in consideration?
Assuming you have an an "X", you may want to consider whether or not you should upgrade the rear axle completely. Depending on what the re-gear will cost you and what your wheeling needs are, you might want to start looking for a dana 44 rear that already has 3.73 or 4.10s in it. I realize these aren't necessarily easy to find, but they are out there, provided you are patient. I just picked one up this past weekend that is a 3.73 limited slip disc brake version. Of course another option is a 8.8 upgrade from East Coast Gear.

The great thing about owning a Wrangler is that there are so many options. The bad thing about owning a Wrangler is that there are so many options!
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Old 04-10-2013, 08:57 PM   #19
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Is yours a manual trans? I've got the 6 speed manual running 33's
No it's the auto 6 speed 3.6 liter
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Old 04-10-2013, 11:01 PM   #20
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Assuming you have an an "X", you may want to consider whether or not you should upgrade the rear axle completely. Depending on what the re-gear will cost you and what your wheeling needs are, you might want to start looking for a dana 44 rear that already has 3.73 or 4.10s in it. I realize these aren't necessarily easy to find, but they are out there, provided you are patient. I just picked one up this past weekend that is a 3.73 limited slip disc brake version. Of course another option is a 8.8 upgrade from East Coast Gear.

The great thing about owning a Wrangler is that there are so many options. The bad thing about owning a Wrangler is that there are so many options!
I wish I could afford to do that

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