regear -or- tuner??
JK Freak
Joined: Jun 2011
Posts: 598
Likes: 1
From: Little Rock
Ok, let me see if this helps put it into perspective for you. I'm using this gear chart:
And this dyno test:
With 33 inch tires, 3.21 gears, at 70 mph, you're turning around 2000 rpms. (I'm assuming that actual measured height of your 33's are about 32.6 inches, and mounted height is about 31.5-32 inches). Now look up at the dyno test. At 2000 RPM's you're getting 250 ft lb's of torque. So, (250x2000)/5252=92 hp. That right on with what the dyno test shows. Now lets do it with 4.11's.
With 33" tires, 4.11 gears, at 70 mph, you're turning about 2520 rpms. According to the dyno test, that is 250 ft lb's of torque. So, (250x2520)/5252=120 hp. That lines up exactly with the dyno, and seems like a pretty decent gain, eh? I'd say so, for sure.
Now back to your original question about tuner (I'm going to toss in CAI & exhaust here too) vs gears. You need 28 more HP with the 3.21 gears to get the same results as the 4.11's in terms of HP. From the claims of our sponsored manufacturers, this is pretty easily attainable, and quite a bit cheaper than paying for new gears + labor.
The reason I picked 70 mph to use as my example is because that is what the gear chart shows. With you mostly driving around town, I think you should wait on the gear choice and save your money in case you'd like to go up to 35's or 37's in the next year or so. In argument to myself, you can buy gears now, but you can't get a tuner quite yet.
Hope this makes some sense - by the way, I might be off on some of my #'s up there, but I think it's all correct. Let me know if I goofed on the math haha.
With the 2011 and previous year models, this is not the case, especially with the AUTO transmissions. If you look, the engine put out smaller torque figures, the 5th gear was too high. That is why you will see guys regearing to 4.56 to run 33's, or 4.88's to run 35's on previous year models.
And this dyno test:
With 33 inch tires, 3.21 gears, at 70 mph, you're turning around 2000 rpms. (I'm assuming that actual measured height of your 33's are about 32.6 inches, and mounted height is about 31.5-32 inches). Now look up at the dyno test. At 2000 RPM's you're getting 250 ft lb's of torque. So, (250x2000)/5252=92 hp. That right on with what the dyno test shows. Now lets do it with 4.11's.
With 33" tires, 4.11 gears, at 70 mph, you're turning about 2520 rpms. According to the dyno test, that is 250 ft lb's of torque. So, (250x2520)/5252=120 hp. That lines up exactly with the dyno, and seems like a pretty decent gain, eh? I'd say so, for sure.
Now back to your original question about tuner (I'm going to toss in CAI & exhaust here too) vs gears. You need 28 more HP with the 3.21 gears to get the same results as the 4.11's in terms of HP. From the claims of our sponsored manufacturers, this is pretty easily attainable, and quite a bit cheaper than paying for new gears + labor.
The reason I picked 70 mph to use as my example is because that is what the gear chart shows. With you mostly driving around town, I think you should wait on the gear choice and save your money in case you'd like to go up to 35's or 37's in the next year or so. In argument to myself, you can buy gears now, but you can't get a tuner quite yet.
Hope this makes some sense - by the way, I might be off on some of my #'s up there, but I think it's all correct. Let me know if I goofed on the math haha.
With the 2011 and previous year models, this is not the case, especially with the AUTO transmissions. If you look, the engine put out smaller torque figures, the 5th gear was too high. That is why you will see guys regearing to 4.56 to run 33's, or 4.88's to run 35's on previous year models.
Last edited by MrDillClinton; Mar 29, 2012 at 06:53 AM.
JK Freak
Joined: Jun 2011
Posts: 598
Likes: 1
From: Little Rock
Average $1000-$1800 for gears and labor.
I'm right there with you on everything except doing the performance upgrades later, and here's why: The Performance upgrades will provide power upgrades no matter what tire size you run. You put them on once, they stay on and work fine. Having to re-gear twice would really eat into my cash flow. Gear's are also a helluva lot harder to switch back to stock in the case that you ever needed to for warranty purposes; they are a much more permanent mod. It's hard for me to justify recommending a gear swap just to run 33's (for the OP) especially when he might be looking at 37's by next summer.
Thanks. Can you tell I've explained it a few times?
People tend to put it off into magical land and not entirely understand it. "I should do this because others say it's what you do when you do x." However if you put it in simpler, easier to understand terms most folks will get it and understand.
Best case is regear AND do the performance upgrades later to get better performance.
People tend to put it off into magical land and not entirely understand it. "I should do this because others say it's what you do when you do x." However if you put it in simpler, easier to understand terms most folks will get it and understand.
Best case is regear AND do the performance upgrades later to get better performance.
Super Moderator
Joined: Jun 2011
Posts: 11,054
Likes: 85
From: Hendersonville, Tennessee
Originally Posted by MrDillClinton
35's is a different story. OD would be useless because there wouldn't be significant RPM's to provide the power. I understand your point about the bicycle gears, but you have to state both sides of the story. Pedaling on level ground in the lowest gear will take a significant amount MORE energy at anything but very slow speeds because you are having to pump those pedals super super fast. There's no way you can talk me into believing that 2500 RPM's puts less stress on a JK than 2000 RPM's at 65 MPH. This would even be more true at lower speeds. The higher RPM's are not NEEDED, although they definitely enhance performance (and engine wear, although it is still a minimal amount).
Edit: I'm only referring to a 2012 Auto.
Anyone here with a Superchips Vivid can use the data monitoring feature to monitor the engine load at different speeds and rpm ranges, and see for yourself. I use mine all the time
You have to remember, there is a difference with what will work, and what will work best
Super Moderator
Joined: Jun 2011
Posts: 11,054
Likes: 85
From: Hendersonville, Tennessee
Originally Posted by AJMBLAZER
Think about it this way.
Your drivetrain basically uses leverage to turn the tires. Sorta like you lifting a certain weight at the end of a teeter totter by pushing down on the other end. Factory setup ideally would be the best combination of distance, height, and length of the lever and position of the load for you to easily push down on it and move the load all day long with minimal fatigue.
Changing the tire size would be like putting a larger weight on the end.
Now it's harder for you to move it.
Now, you may be strong enough that you can just push a tiny bit harder and up it goes. May never notice it. May notice it only after a good long time of doing it. It is however harder.
Putting larger, heavier tires on and not regearing would be akin to putting a larger load on the end and expecting you to still be able to move it with the same setup as the original. You may be able to do it but it will be further from ideal the heavier the weight gets and you'll notice it more and more.
Regearing would be akin to moving the balance point and/or changing the position of the pivot and the load on the other end. You end up restoring the setup to some configuration that results in you putting as close to the original effort as possible.
A tuner or headers or supercharger or exhaust or whatever other performance mod would be akin to you pushing down harder on the lever in order to make up for the lost leverage over the heavier weight. It works but again, you're working harder.
Now, let's complicate it further.
In the real world we're also dealing with tires of varying heights and weights, your intended use, your "seat of the pants" butt dyno and personal tolerance, how big of a change from stock you are making, and the way your particular drivetrain makes and puts power to the ground.
I know turbo diesel truck guys making huge honking numbers that have 35's or bigger with 3.55 gears. They have so much torque that they honestly don't notice the difference. Is it there? Yes. It just doesn't matter much when you're making 400ft/lbs of torque at idle.
As said above you may want to slap the tires on and see how you like it. Grab the ProCal, recalibrate your computer for the tires so your auto trans shifts correctly (this is important!), and drive it. If you don't mind, it don't matter. If you do...how bad is it? Seem just a little bit slower? Maybe you can slap a K&N in the filter housing and a freer flowing muffler in place of the factory constricted junk. I've personally done something similar with minor tire changes and had it work out well enough that I never took the time to do more.
If you find it noticeably slower off the line and don't like it then it may be time to start saving for a gear change.
Gear change = restoring the system to the stock "leverage". You're reconfiguring the teeter totter and load setup so that you have to put about the same effort into pushing down on your end.
Performance mods = adding more power to hopefully make up for the additional power your now "out of balance" system needs to move the vehicle. You're putting more effort into pushing down on your end of the teeter totter but maybe you've done some 'roids and bulked up and don't notice as much. Still, leverage wise, the system isn't in balance as it was originally.
Again, YMMV and opinions differ and what some people can live with for thousands of miles or tens of thousands of miles others hate on the first drive.
Your drivetrain basically uses leverage to turn the tires. Sorta like you lifting a certain weight at the end of a teeter totter by pushing down on the other end. Factory setup ideally would be the best combination of distance, height, and length of the lever and position of the load for you to easily push down on it and move the load all day long with minimal fatigue.
Changing the tire size would be like putting a larger weight on the end.
Now it's harder for you to move it.
Now, you may be strong enough that you can just push a tiny bit harder and up it goes. May never notice it. May notice it only after a good long time of doing it. It is however harder.
Putting larger, heavier tires on and not regearing would be akin to putting a larger load on the end and expecting you to still be able to move it with the same setup as the original. You may be able to do it but it will be further from ideal the heavier the weight gets and you'll notice it more and more.
Regearing would be akin to moving the balance point and/or changing the position of the pivot and the load on the other end. You end up restoring the setup to some configuration that results in you putting as close to the original effort as possible.
A tuner or headers or supercharger or exhaust or whatever other performance mod would be akin to you pushing down harder on the lever in order to make up for the lost leverage over the heavier weight. It works but again, you're working harder.
Now, let's complicate it further.
In the real world we're also dealing with tires of varying heights and weights, your intended use, your "seat of the pants" butt dyno and personal tolerance, how big of a change from stock you are making, and the way your particular drivetrain makes and puts power to the ground.
I know turbo diesel truck guys making huge honking numbers that have 35's or bigger with 3.55 gears. They have so much torque that they honestly don't notice the difference. Is it there? Yes. It just doesn't matter much when you're making 400ft/lbs of torque at idle.
As said above you may want to slap the tires on and see how you like it. Grab the ProCal, recalibrate your computer for the tires so your auto trans shifts correctly (this is important!), and drive it. If you don't mind, it don't matter. If you do...how bad is it? Seem just a little bit slower? Maybe you can slap a K&N in the filter housing and a freer flowing muffler in place of the factory constricted junk. I've personally done something similar with minor tire changes and had it work out well enough that I never took the time to do more.
If you find it noticeably slower off the line and don't like it then it may be time to start saving for a gear change.
Gear change = restoring the system to the stock "leverage". You're reconfiguring the teeter totter and load setup so that you have to put about the same effort into pushing down on your end.
Performance mods = adding more power to hopefully make up for the additional power your now "out of balance" system needs to move the vehicle. You're putting more effort into pushing down on your end of the teeter totter but maybe you've done some 'roids and bulked up and don't notice as much. Still, leverage wise, the system isn't in balance as it was originally.
Again, YMMV and opinions differ and what some people can live with for thousands of miles or tens of thousands of miles others hate on the first drive.
JK Newbie
Joined: Feb 2012
Posts: 47
Likes: 0
From: Ferdinand in
Originally Posted by Ryan0260
How would overdrive be useless? If a vehicle is geared properly in relation to the tire size and the shift points are corrected, the overdrive will work fine. You can't base everything by rpm's, as not all motors operate efficiently at the same rpm. The 3.8 and 3.6 motors likes the higher rpm's. That's how they were designed. 2600 rpm's is nothing to these motors. I can tell you that with 35's, 2000 rpm's is lugging the crap out of the motor trying to turn those big tires. Why? Because these motors don't produce much power and torque at 2000 rpm's.
Anyone here with a Superchips Vivid can use the data monitoring feature to monitor the engine load at different speeds and rpm ranges, and see for yourself. I use mine all the time
You have to remember, there is a difference with what will work, and what will work best
Super Moderator
Joined: Jun 2011
Posts: 11,054
Likes: 85
From: Hendersonville, Tennessee
Originally Posted by frick316
I have the vivid. Don't like all the shifting on the interstate running 75 mph with 33x12.50 tires. What are your suggestions on tuning if you have found a good setting
JK Newbie
Joined: Feb 2012
Posts: 47
Likes: 0
From: Ferdinand in
Originally Posted by Ryan0260
Best suggestion would be to get the advanced transmission tuning installed, and get with jpop on a good startere shift schedule. Other than that, make sure speedo is calibrated and turn the OD off until you can re-gear
JK Freak
Joined: Jun 2011
Posts: 598
Likes: 1
From: Little Rock
How would overdrive be useless? If a vehicle is geared properly in relation to the tire size and the shift points are corrected, the overdrive will work fine. You can't base everything by rpm's, as not all motors operate efficiently at the same rpm. The 3.8 and 3.6 motors likes the higher rpm's. That's how they were designed. 2600 rpm's is nothing to these motors. I can tell you that with 35's, 2000 rpm's is lugging the crap out of the motor trying to turn those big tires. Why? Because these motors don't produce much power and torque at 2000 rpm's.
Anyone here with a Superchips Vivid can use the data monitoring feature to monitor the engine load at different speeds and rpm ranges, and see for yourself. I use mine all the time
You have to remember, there is a difference with what will work, and what will work best
Anyone here with a Superchips Vivid can use the data monitoring feature to monitor the engine load at different speeds and rpm ranges, and see for yourself. I use mine all the time
You have to remember, there is a difference with what will work, and what will work best
And, just so you will know, the 3.6 pentastar puts out the EXACT same amount of torque at 2000 RPM's as it does at 2500 RPM's.
You're making comments about the 3.8 engine, which aren't necessarily true for the 3.6, and the OP has a 2012. 2000 RPM's is not lugging the motor in a 2012 JK, neither is 1500 RPM's.
If you'll see my post above, you'll notice that with the 3.21's and 33's that the OP was asking about, his 2012 JK is putting out more horsepower than a 3.8L JK would be with 4.11's and 33's.
Edit: here's the figures, since I doubt you guys want to add it up for yourself.
A 3.8L JK Auto with 33's and 4.11 gears is turning 2100 RPM's @ 70 mph and putting out about 205 ft lbs of torque. (205x2100)/5252= 82 HP.
That is less HP than a 2012 Auto with 33's and 3.21's. That is why I'm telling the OP that regearing is not AS necessary for the setup he wants to run - its widely accepted that 4.11's and 33" tires are fine for 2007-2011 JK's. If this is true, then 3.21's and 33's will be even better for the OP's 2012 Auto.
Last edited by MrDillClinton; Mar 29, 2012 at 05:37 AM.