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Superchips FlashCal

The best solution for calibrating your Jeep or Truck.

The FlashCal is a great tool for calibrating your ECU to properly make adjustments for your aftermarket parts that you have installed. On top of calibration, the FlashCal offers some great settings for your various lights and accessories, including options to turn on and off your lights and /or horn when you lock your vehicle.

For the most part, I’m going to focus this review and explanation of the FlashCal on Jeeps. We find that the FlashCal is most popular among Jeep owners, and the reason isn’t lost on us. The FlashCal is great for Jeeps. However, we sell plenty of FlashCals for Trucks too, so keep in mind that when I’m talking about Jeeps, most of these Calibration modifications, with the exception perhaps of Rubicon Lockers, are also available for Trucks via the FlashCal for Truck line. And you can purchase both versions, FlashCal for Jeep and FlashCal for Truck, on this very page.

Before we get too deep into exactly what the functionality of the FlashCal is, we’d like to make a quick disclaimer and explanation:

The FlashCal is NOT a TUNER. It can NOT tune your vehicle.

If you would like to tune your vehicle and want all the functions that the FlashCal has to offer, you should pick up a FlashPaq, also made by Superchips. If you already have a FlashCal and are now screaming at the computer because you think you bought the wrong thing, do not panic. Through Superchips website, you can pay the difference between the cost of the FlashCal and the FlashPaq to upgrade and update your FlashCal via your home computer using the powers of the Interwebs to convert that Cal into a FlashPaq. You don’t save any money by doing it this way, and it is certainly more of a hassle than just getting the FlashPaq in the first place. Nevertheless, if you ordered wrong or if down the road you decide you do want to upgrade to tuning, you most certainly can do so via the Internet.

Now that that’s over with, let’s breakdown all the features and settings of the FlashCal. Do note that the FlashPaq also has all of the features, plus the ability to tune your vehicle.

The FlashCal & ALL those Options Settings

First, the FlashCal has a lot of Options. So let’s just throw that out there. 13, count ‘em, 13 different settings under Options. Now for the most part, you will likely set these and forget ‘em, but there are a few that you might tinker with on the reg. Some of these are great reasons to buy a FlashCal, and others might just be cool bonus features. Regardless, I’m going to lay them all out, then go through each one by one, explaining in-depth why you might need a FlashCal.

To start up the FlashCal, you’ll first want to hook it up to your computer and update it. Then you will want to plug it into your OBDII port with the engine off. Next take your key, put it into the ignition, and move it to the Auxiliary position or Run position, the one you use when you just want the radio on or to roll up your windows. In other words, don’t start the vehicle. Just turn the key until the radio and such comes on.

The FlashCal will then communicate with your on board computer, your ECU. It will collect information about your vehicle, including your vehicle’s VIN. Once it has established all of this, a menu screen will pop up, and you’ll be able to use the arrows to navigate from one selection to the next. The new FlashCal has only one large icon on each page, so to speak, so you’ll likely see Options first, and then if you hit right or left you’ll scroll through Scan and Info as well.

Let’s start with the Options, as this is where you will spend most of your time calibrating.

A Complete List of FlashCal Options

Here’s a full list of all the Options that will be listed (on some makes and models, some of these may be disabled or not have as many adjustment possibilities):

Axle Lock

Engine Idle

Tire Size

Gear Ratio

TC Hi/Low Ratio

Lamp Delay

Run Lights

Acc Delay

Lane Change

Lamp Flash

Horn Chirp

TPMS Offroad

Fog Lights

Now, I don’t know about you, but the first time I saw that list, I knew what some of those likely meant. I was like, Run Lights, that’s probably my Daytime Running Lights. And guess what, I was right. Others, like Acc Delay, I wasn’t totally sure. So we’re gonna run through each and every one of these Options, tell you what they offer, why you might use them, and if you shouldn’t use them unless you’ve already made another aftermarket upgrade to your Jeep or truck.

The top five options or so on the list are likely the main reasons most Jeep owners pickup the FlashCal. I might throw the TPMS Offroad option on there as well. The others are really cool and certainly add value to the FlashCal, but typically when you’re dropping $150 on a device, you’re not doing it so you can change your running lights to Euro mode only. But hey, each there own. I like Euro mode. It’s fun.

Axle Lock

Sometimes referred to as Rubicon Lock because this function allows you to use your Rubicon lockers while in 4-HI, Axle Lock will allows you to lock the front or rear differential, even in 4-HI mode, though you shouldn’t go over 30 MPH like this (which why would you).

What does Axle Lock do?

The Axle Lock function will allow you to lock either the front or rear axles via the differential. Stock Rubicons can already do this, but not in 4-HI mode, only in Low.

Why might you want to use Axle Lock?

This function is largely used by those in the off-road community. If you are losing traction with one front or rear wheel, locking that axle will force both wheels to spin at the same speed. So if you are off-roading, and one wheel is just spinning in the air and you aren’t getting enough torque to the wheel that is actually making contact with something, you can lock that differential up to force it to spin at the same rate. This is essential for off-roading. And it comes stock on the Rubicon, but you aren’t able to do it in Hi gear.

(When) Should you use Axle Lock?

If you are a serious off-roader, there could certainly be times when this function will be essential. My example of having one tire up off the ground is certainly a good time to try locking that axle. You might also want to use this function when attempting to climb a steep hill, boulder, or cliff face. Off-roaders seem to be divided on the 4-Hi part. Some claim that they are able to crawl just fine in Low while locking one diff or the other in these types of situations. Others swear by this function.

The truth is, whether or not you can get through sticky off-road situations in low gear or not has a lot to do with your crawl ratio, which has a lot to do with your engine, your transmission, your transfer case, your gear ratio at the axles, and how big your tires are--not too mention how much traction they have. In other words, it depends. In general, this functionality could only help you when off-roading.

Do not that it could be very dangerous to drive over 30MPH with your differential locked, not just for you as the driver, but it could damage your vehicle. I can’t imagine why you would need to lock it up and go over say 15 MPH when off-roading, but maybe someone else can come up with a scenario that I just haven’t thought of or encountered yet.

Engine Idle

One of the more obvious functions, I hope. Engine Idle allows you to adjust your engine idle speed.

What does Engine Idle do?

The Engine Idle option allows you to speed up or slow down your Engine Idle speed to a limited degree.

Why might you want to make Engine Idle adjustments?

If you are idling too high, you might want to crank it down a bit to save on fuel economy for instance. You’ll notice this if your RPMs are really high when you are just sitting at a standstill. If this is happening, you might want to consult with your friendly local mechanic. You could use this function to try to make a minor adjustment yourself.

Most Jeep owners might use this function to up their Idle temporarily when using an accessory that might require more power, such as a Winch.

(When) Should you use Engine Idle adjustment?

If you do use a Winch often when off-roading, or just off-roading in general, might be a good reason to take a look at this function. If your engine is idling really high or low in normal everyday driving conditions on the road, we would personally recommend taking it to a mechanic to have a look at it. A simple under the hood adjustment could correct your idle without you having to mess with your ECU. On the other hand, if you were on the road and didn’t have time to take your vehicle in, this function could be used as a temporary fix.

In general, I would only use this if I made serious changes to my engine’s idle under the hood or if I needed to temporarily up my idle while off-roading and /or using a winch.

Tire Size

Probably the number one reason Jeep owners purchase the FlashCal, this option lets you tell your ECU what your proper, new tire size is.

What does Tire Size do?

This option lets you adjust your tire size in inches, so that your Engine Computer Unit knows what your size the tires you have installed are.

Why might you want to adjust your Tire Size?

If you install or plan to install larger tires (or smaller for some reason) this is definitely something you should adjust. Having larger tires installed will cause your speedometer to be wrong, for instance. Furthermore, your engine will not know that you have larger tires on. So your vehicle will be functioning under the assumption that you’re still rocking stock tires.

If you plan to off-road, chances are you will need larger tires for better clearance and traction. But you will need to tell your ECU that you have installed larger tires if you want your vehicle to function at optimal parameters. This function is a must have if you off-road and install larger tires.

(When) Should you use Tire Size adjustment?

If you install new tires that are larger than stock, you should definitely use this function. Not only will it improve your fuel economy, but it will make your whole engine and drivetrain function more efficiently, including providing you more power and torque at each wheel, all of which is incredibly important for off-roading. So yes, use this if you have aftermarket tires. The FlashCal can handle tires between 22.5” and 42”. If you go smaller or bigger than that, you’re on your own.

Gear Ratio

Another important adjustment for off-roaders and aftermarketers in general. If you have larger tires, you should upgrade your axle gear ratio. And if you do, you gotta tell you ECU.

What does Gear Ratio do?

This function lets you tell your onboard computer that you’ve modified your axle gear ratio at rear or front by replacing your gears with aftermarket ones.

Why might you want to adjust or alter your stock Gear Ratio?

Many off-roaders modify their gear ratio for two reasons: they added on larger tires, and related to that, they want more torque at their wheels.

(When) Should you make a Gear Ratio adjustment?

You would only adjust your Gear Ratio using the FlashCal if you installed an aftermarket Axle Gear or had someone do it. This is certainly something you should consider if you are using larger tires than stock. But if you have not installed a new gear at one of your axles, then you do not need to be playing around with this function.

With all that being said, if you increase your tire size, you should seriously consider upgrading your gears. Just going up one to two inches in size can mess with your fuel economy and horsepower at the wheel. Upgrading your axle gears is a great way to correct this and get the most out of your engine and your sweet new tires. And once you’ve installed the new axle gear (or gears if your 4x4), then you’ll need a device like your FlashCal to communicate with your ECU and tell it how to function optimally with your new axles and tires.

Basically, this adjustment is similar to the Tire one. If you put on bigger tires, you should adjust your tire size using the FlashCal so your ECU knows the new parts. Likewise, if you install new axle gears, you need to tell you ECU using the FlashCal.

For more on Gear Ratios, check out our Nerding Out on Gear Ratios. 

TC Hi/Low Ratio

Related to gear ratios, your TC or transfer case ratio may need to be adjusted if you’ve installed a new aftermarket transfer case. Some makes /models can only adjust the Low Ratio, while others appear to be able to adjust your high too. Be warned. Off-roading, adjusting the low gear is probably what’s most important anyway though for most users.

What does TC Hi/Low Ratio do?

This option allows you to tell your ECU that you have installed an aftermarket transfer case with a different ratio than the stock one. As your Transfer Case Ratio is a crucial component to your Crawl Ratio, many off-road enthusiasts install aftermarket transfer cases to try to maximize their off-road abilities.

Why might you adjust your TC Hi/Low Ratio?

The only time you should be adjusting your transfer case ratios is if you installed a new transfer case that has different gearing inside of it that your stock transfer case did. Off-roaders are looking to maximize torque at their wheels so that you can climb obstacles and drive through mud and such better. Installing an aftermarket transfer case can improve your ability to do so, though your stock transfer case in a Jeep is already pretty badass especially compared to say a sedan or mini-van, for example.

(When) Should you adjust your TC Hi/Low Ratio?

After installing an aftermarket Transfer Case that has different gear ratios than your stock TC, you should definitely use a product like the FlashCal to tell your ECU that you upgraded your transfer case if you want your drivetrain to function properly and efficiently.

Upgrading almost any of these aftermarket parts, whether it be bigger tires / wheels or a new gear ratio at your axle or a new transfer case, without telling your ECU about it is like driving your 4x4 capable vehicle in 2WD mode while off-roading. You’ve got all this great capability that your just wasting because your engine doesn’t even know its there, or worse yet, your engine is working against it because it still thinks you’re rocking those crappy stock parts.

I mentioned Crawl Ratio in the last section, but I didn’t bother to go into what exactly that means. Check out our video Nerding Out on Crawl Ratio for the low down. And if you already know all about that jazz, then let's move quickly through the other settings. 

A Note on the Rest of the Options

You’ll notice that from here on, there isn’t nearly as much information under each different option. That’s because the ones above require some explanation and advanced information, whereas most of the rest of the options are merely cosmetic or simply require less of an explanation. That doesn’t mean they aren’t useful Options, but as I said before, those first few options plus the TPMS one are probably the ones that draw the eyes or the main reasons Jeep owners are interested in buying a FlashCal.

Lamp Delay

Think: Head Lamp Delay or Headlight Delay.

What does Lamp Delay do?

This option adjusts how long your head lamps or headlights stay on after you turn off the vehicle. It can be adjusted all the way up to 120 seconds (2 minutes) and down to 0 seconds for an instant shut off effect.

Why might you want to adjust your Lamp Delay?

There could be any number of cosmetic reasons why you might want to adjust how long your headlights stay on after you shut off your vehicle.

(When) Should you adjust your Lamp Delay?

For me, the most common reason has been that we went camping, but we got a late start, and now I’m trying to set up the campground in the dark with a small propane lantern that just keeps going out, so I turn my vehicle’s headlights on but they keep going off, so I set the delay to 2 minutes and ask my wife to sit in the truck and keep turning it to Run and then Off again every time the lights go out. But maybe that’s just me.

A more pragmatic reason might be that you’re a private eye and you don’t want your headlights to stay on after you turn off your vehicle so it won’t call attention to you.

Whatever your reason, this function is definitely something fun to play around with.

Run Lights

Think: Daytime Running Lights.

What does Run Lights do?

This option allows you to adjust how you want your lights to function during the day and/or as turn signals.

For most makes / models, here’s the list of options that will be presented to you:

High Beams

Low Beams

Turn Signals

Fog Lights

European Lights

No Running Lights

Why might you adjust your Run Lights settings?

Most of these are pretty self explanatory. If you want all your lights to at like High Beams putting out maximum light, then you choose that. If you want them to be like Fog Lights, pick that one. The Turn Signal function is pretty cool as it changes your running lights into additional Turn Signals or Blinkers in Back Woods lingo. Just playing. That’s what we call ‘em around here.

European Lights?

I had no idea what European Lights were, so I had to do some digging. Here’s what I found out:

In many places in Europe, there are certain light restrictions concerning running lights, apparently. The quickest way to sum it up is this: US running lights be too bright. There. I said it. So setting your running lights to Euro mode will make it so that they will be on the Low Beam setting only that’s too bright too, so they will also be at half intensity. That’s right. Half intensity low beams, because we wouldn’t want to blind anyone with our shiny daytime running lights.

Also note that when in this mode, and some of the others too, the daytime running lights only come on when your Jeep is not in park and doesn’t have the parking brake on.

(When) Should you adjust your Run Lights?

This is completely up to you really, but you might kick it into High when driving through the back woods at night, so to speak. Or you might have the turn signal function on during a highway commute because it might make it easier to see that you intend to change lanes. Fog lights are almost always good for foggy conditions. Seems pretty obvious.

Oh, and European lights are essential if you’re gonna be driving in parts of Europe where you might get a nasty ticket for having daytime running lights that are just too bright. I wish I was making this stuff up, but I’m really not.

And the no running light thing, see the private eye thing above. Yeah, that’d be a good time to have no running lights at all. Fun.

Acc Delay

Think: Accessory Delay, like your Radio and/or anything that requires power through an auxiliary power socket.

What does Acc Delay do?

This function allows you to set how long the Radio and other powered accessories will stay on after you turn off the vehicle. You can set it to 45 seconds, 5 minutes, or 10 minutes. If you open your driver’s side door (maybe passenger side on some makes / models) everything will turn off anyway.

Why might you adjust your Acc Delay?

If you want any accessories and/or the radio to stay on even after you’ve turned off the engine this could be a great function for you.

(When) Should you adjust your Acc Delay?

My immediate thoughts were at the old school drive-in movie theater or maybe a Sonic. Any place where you might want the radio and other accessories to function for up to 10 minutes but you don’t necessarily want your engine roaring along with them.

Lane Change

Think: Turn Signal or Blinker. I think the Brits call them Flashers, maybe? Turn Flashers? Sure…

What does Lane Change do?

Lane Change allows you to toggle on and off the one touch lane change feature. This ability makes the turn signal or indicator flash three times when you just touch the turn signal once.

Why might you toggle Lane Change?

If you do a lot of highway driving or commuting period, this feature may make it more clear that you are about to change lanes. Furthermore, some drivers just like this options as you don’t have to put the indicator on and then turn it off after changing lanes. You just touch it once and it flashes three times.

(When) Should you use Lane Change?

This function is great for long commutes and heavy traffic. I personally dig this one because I hate having to turn my blinker on and off all the time. Simply being able to auto flash them three times to show my lane change intentions is way more efficient. Plus it looks way cooler.

Lamp Flash

Think: Flashing your brights when you lock your vehicle.

What does Lamp Flash do?

This function allows you to toggle on and off whether your headlights flash on when you lock your vehicle.

Why might you toggle Lamp Flash on /off?

If you live in an area where you don’t want your lights to flash because they may wake someone up or alert someone to your presence (see that P.I. thing just never ends does it?) with your flashing lights. Conversely, if you often forget to lock your vehicle and have to press the little lock button on your key fob from far away, the flashing lights may let you know that you did indeed manage to lock your vehicle that time.

(When) Should you toggle Lamp Flash?

Again, this one is up to you. Some of us like that flash of light to let us know we locked or unlocked our vehicle. Some don’t. I know sometimes I get home late at night, and I don’t want my lights to flash when I lock up in front of my house. But there are other times when the flash lets me know that I did get the truck to lock correctly from afar. This one really depends on your personal preference.

Horn Chirp

Think: Sounds horn when you lock your vehicle.

What does Horn Chirp do?

This function toggles the horn sounding when you lock your vehicle.

Why might you toggle Horn Chirp on /off?

This is very similar to the Lamp Flash. Some people like the noise. There may be times when it might be annoying to you or others around your vehicle.

(When) Should  you toggle Horn Chirp?

If you live in a quiet area and often come home late at night and don’t want to wake anyone up by locking your vehicle, you should toggle this one off. If you need to lock the vehicle from afar during daytime hours, this might be a good one to have on.

If you regularly lock your vehicle, as you are walking into a building, say to go shopping, while your husband is holding the baby walking right in front of your hood where the horn is going to be super loud, scaring both him and the baby half to death, you really--and I’m gonna emphasize that--really consider turning off your Horn Chirp function, please, sweet heart? I love you, but sometimes that horn chirp is just too much for me and the kiddo.

TPMS Offroad

And now for the final big one: the TPMS toggle. The menu labels it also as TPMS Disable / Offroad Mode.

What does TPMS Offroad do?

This feature allows you to turn your TPMS or Tire Pressure Monitoring System on or off.

Why might you toggle TPMS off?

This function could be a good one to trigger when you are going to lower your tire pressure so you can go off-roading or Jeep crawling.

(When) Should you toggle TPMS off /on?

Off-roading is a great time to turn this off. If you are lowering your air pressure in your tires to increase grip / traction, your TPMS might be going crazy the whole time. Likewise, if your TPMS has malfunctioned and you just haven’t had the time to get it fixed yet, this can be useful.

I would recommend having your TPMS on when you are on the highway and during travel in general because it could alert you to a sudden leak or drop in tire pressure. Likewise, if you live somewhere where the temperature change through the seasons causes tire pressure to need minor adjustment, your TPMS can tell you when you need to top her off and when you should let a little bit out.

Fog Lights

Think: Makes fog lights more like headlights.

What does Fog Lights do?

This setting allows you to link the fog lights up to your high beams so that they will only turn on when your brights are on.

Why might you toggle Fog Lights to your High Beams?

If you only want your fog lights to come on when it is foggy and you always turn on your high beams during these conditions, this might be a good option for you over just leaving your fog lights on all the time. However, personally, I like my Fog lights on with my Low Beams during foggy conditions.

(When) Should you link your Fog Lights to your Highs?

If you are driving through the back roads often at night and want your fog lights on with your highs, this function is great for you.

Likewise, if for dramatic effect, you want to be able to pull up slowly, with all your lights off, say because you’re about to get the jump on somebody you were doing a stake out on cause you’re a private spook, and then suddenly go from no lights on at all to full Brights and Fog Lights blasting this guy in the face, then you have gotta turn this one on for that buddy.

And that covers all 13 options pretty thoroughly, don’t cha think?


The Scan Menu will present you with three options:


Gauges and Data Log

Battery Voltage

These three are pretty self explanatory, but I’ll explain them just the same briefly.


Another great reason to pick up a FlashCal is so you can read and clear your own DTC’s or Diagnostic Troubleshoot Codes. These are the codes that your ECU gives out when your check engine light and other diagnostic lights display on your dash.

Being able to read DTC’s can be really useful, especially if you do a lot of work on your vehicle yourself. I’m a DIY kinda guy. I love being able to read and clear my own DTC’s. Sometimes the codes are something very serious. Other times they are simple reminders that can be easily cleared. Personally, I like the peace of mind that being able to check them myself gives me.

Keep in mind that most automotive parts dealers will check your codes for free too, but if you’re like me, you probably hate having to go up to the auto parts place to ask some guy to come out and check your codes, so the Scan function is yet another great reason to pick up a FlashCal.

Gauges & Data Log

This function allows you to monitor and record data on up to 4 different parameters over time and then export that data via computer.

If you are into racing, truck pulls, or just like to know the max values you hit while off-roading, this function is going to be useful to you. Personally, I love numbers, so anytime we can gauge and record something that I couldn’t already easily observe from stock gauges, I’m down--even if that data isn’t really that useful to me. I just like knowing what’s going on with my vehicle.

If you aren’t into such things, you probably won’t use this function at all and certainly you aren’t required to do so.

Battery Voltage

While you probably have a gauge or at least a check engine light that notifies you if your battery is very low, this function allows you to measure exactly how many volts your battery is giving out. Personally, this function is pretty amazing for me, and if you’ve ever had your vehicle not start, then you know what I mean.

Here I am, thinking maybe my starter’s gone out or I’m gonna have to replace my alternator, and a simple quick check from my FlashCal tells me my battery is dead. Easy. Again, you might not use this daily, but when you need it, the Battery Voltage checker is pretty useful.


The final menu is titled Info. This one only has two options: VIN and Device.

The VIN displays your vehicle’s VIN or Vehicle Identification Number. Sometimes you need to know this information for insurance reasons or when you’re buying a new vehicle or trading it in. The FlashCal reads this from your ECU. You can also find this number up on your dash typically, along the windshield.

Device Info displays the model and last time you updated your FlashCal itself. You might check this periodically to double check when you last updated it, or if you see online that there is a new update, you could check to see if the update number matches what your FlashCal displays here.

Upgrading your FlashCal to a FlashPaq

That pretty much does it for the FlashCal. If you pick up a Cal and ever decide that you do want to try out some custom tuning, you can upgrade your FlashCal to a FlashPaq for a fee online directly from Superchips. A simple update via the Internet will then give you the ability to start tuning your ride.

And in case you were wondering, the FlashPaq has all the functionality of the FlashCal plus more with the added custom tuning. I cannot tell you how many times a custom has bought a Cal thinking they could tune and then been able to update it. Likewise, we’ve had many customers tell us later that they ended up upgrade to the FlashPaq eventually to try out the tuning and that they were very pleased with the performance gains (and even mileage gains) the tuner gave their Jeep.

Regardless of whether you’re looking to pickup a FlashCal or FlashPaq, we hope you’ll get yours from Midwest Aftermarket. Not only is our research top notch, but our customer service is too. Our collection of calibrators, Jeep tuners, pickup bed covers, truck running boards, and much more includes all the leading styles and brands. Midwest Aftermarket is the #1 online retailer for aftermarket truck and Jeep accessories, selling products at the lowest prices and providing the best customer service in the industry. With the goal to provide the highest quality product with the fastest shipping at affordable prices, look no further for your vehicle’s aftermarket accessories. From UTV’s to Jeep-fanatics to F150’s or Chevy Silverado’s, Midwest Aftermarket will give you the customer support you deserve.

Nerding Out About Gear Ratios

If you’re replacing your Axle Gears yourself, here’s some fun info for you.

Your Gear Ratio is the number of teeth on your ring divided by the number of teeth on your pinion, rounded to the hundreds position, or 3 digits like so: 3.55.

It is also likely that your Gear Ratio is stamped onto the pinion shaft somewhere, so if you hate math, there’s that.

Every pinion and ring is designed to work together specifically. You canNOT mix and match them.

If you have upgraded your tires and that’s why you are adjusting or swapping out your gears, then you need to know what gear ratio you should swap to. Here’s how you can figure it out:

Take that Old Gear Ratio, multiply it by a New Tire Size in inches, then divide it all by the Old Tire Size. This should give you the New Gear Ratio or pretty darn close to it. You probably can’t hit it exactly, but if you’re within a few hundredths, you’ll be fine. The closer, the better.

In general, the higher your gear ratio number is, the lower the gearing will be, hence the more low end power and torque you’ll have at the wheels. This is why a lot of off-roaders install aftermarket gears with higher gear ratios, on top of the larger tires and wheels.

Conversely, lower gear ratio numbers offer better gas mileage, but they are not good for maxing out power and /or torque, so they aren’t great for your Jeep if you’re going off-roading, and to date, I have never met anyone who bought their new Jeep JL so that they could try to get great gas mileage. I suppose there could be someone like that out there, but I haven’t met ‘em yet.

If you decide to start playing around with your gear ratios, be careful about Carrier Breaks. Some Jeep models can only handle gears that are so big. Make sure before you purchase new gears that your vehicle can actually handle gears that size. If not, you’ll find yourself with some sweet new axle gears that won’t actually fit in your gearbox. Sigh.

Nerding Out on Crawl Ratio

I mentioned Crawl Ratio in the last section, but I didn’t bother to go into what exactly that means. If you bought your Jeep at the dealership, chances are they through out some number like 73 as your Crawl Ratio or something. And that’s a nice number, no doubt. But they may not have gone into the detail of explaining what the heck it means. This feels like just as good of a place and time as any, so here we go.

What is Crawl Ratio?

Crawl Ratio is a term used to describe the amount of torque at your wheels compared to the amount put out at your flywheel under the hood. It can easily be calculated by multiplying several gear ratios together: your transmission’s gear ratio when in 1st gear, your transfer case’s when in Low, and your differential axle gear ratio. The number you get, in that example it was 73, is the amount by which your flywheel torque is multiplied to get your ideal torque at your wheels.

Of course all of this is in ideal settings and such, so you won’t actually get that amount of multiplication, but you may get pretty darn close.

Crawl Ratio is important if you like to go off-roading, or Jeep Crawling. It’s all starting to make sense now, isn’t it? And if you regularly go off-road in your Jeep, you likely already new about all of this. These guides are designed for those just getting into modifying and upgrading their Jeeps, after all. So bear with me.

In general, the higher your Crawl Ratio, the better you will be able to transverse difficult off-road terrain. You can improve your Crawl Ratio by increasing your tire size, upping your Gear Ratio at the Transfer Case or Axle by installing aftermarket gears with a larger ratio, or by getting more torque out of your engine in the first place. And that last part is important. Remember that you can improve the multiplier (the Crawl Ratio) itself by upgrading gears and wheels, but you can improve your output at the flywheel too by making engine adjustments and tuning (though you’d need a FlashPaq for that, wouldn’t ya? Time for an upgrade?).

Do keep in mind that while a high Crawl Ratio is great for off-roading, it is not so great for gas mileage, so don’t be surprised if after raising your Crawl Ratio in any number of ways you find that your MPG’s inversely were affected. Either find a sweet spot in the middle, or choose which you want to max out. I’ll guess that if you’re maxing Crawl Ratio you’re doing it on your off-road weekend warrior badass Jeep. And if you’re maxing fuel economy it’s with your daily driver.