“Self adjusting speedometer” ??

RMojitoJL

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Some dealers have well trained and knowledgeable people there in the service and sales areas. Most dealers simply suck - that's the reality and they don't give a $h*t one way or the other. Get you in and get you out after you pay. They don't want to do bs stuff to them and don't actually care to get you the correct into. This isn't a Jeep thing, this is in general. A dealer wouldn't be installing my lift, aside from them over charging in most cases… I would rather do it myself or have an offroad shop do it that has done many and that's what they do day in and day out.
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WranglerMan

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I think the dealer telling you the speedo with fix itself is pretty funny and sad at the same time, he may be confusing the speedo recal with the transmission relearning shift points on its own once you go to larger tires.

As far as the speedo goes I’m not sure what a dealer charges but have heard $150-$250 and it’s a one time service deal, IMHO you are better off getting a programmer and doing it yourself, it’s a simple process
 

FPrice

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I have a Rubicon with 35x12.50x17 Toyo MTs on Method rims.

I plugged in my phone and drove down the freeway. I checked my speed on the dash with the gps speed on my Navionics app.
70mph on the dash, 70 on the Navionics app! Magic!

Then I unplugged my phone (CarPlay) and checked. 70mph on the dash, 74.8 on the Navionics app....not magic.
 

JxRYE

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Local government decided to install one of those stationary speed signs that displays your speed. Before my lift and bigger shoes it was spot on and so was the app I downloaded on my phone. After the tires everything was out of wack, so in came the tazer mini which I am loving! No longer have to worry about speed, don't have to hit the auto start on/off anymore, my kids love the light show it can do now(not sure why that is even a thing? christmas parades?), etc.
 

Al13

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Who was the dealer so I don’t go to them? I live in Franklin TN.
I forgot to add that my dealer told me they recalibrated my speedo when the changed my wheels and tires, no charge.
 

OnNightfall

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I did 35s with no lift, it was getting 13mpg on the highway before I recalibrated, it would not go in to 8th gear.
After the recal it shifts in to 8th a bit easier and gets better mpg city and highway.
Is this true? Does calibrating Speedo really improve mpg and get you in 8th gear on the highway?
 

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Is this true? Does calibrating Speedo really improve mpg and get you in 8th gear on the highway?
The short answer is no, to effectively get back to stock gearing as in seeing 8th gear like you did when first got you
JL you would have to regear after going to larger tires, as far as the speedo goes haveing it calibrated is not going to give you better MPG’s it’s just going to give you a more accurate number as the average MPG is based on the speed recorded and if it’s off due to tire size it’s going to give you an incorrect number

I know this first hand, my stock JLUS was getting 20-22 HWY then added the 315 KO2’s and calibrated with Tazer and speedo is spot on and my MPG’s dropped to 18-19 and then I just added a bumper and winch and now getting 17.5-18.5

The JL will relearn shift points after a short period but you are not going to gain back the MPG you lose from going to larger tires, it’s not just the speedo that effected its the rolling mass of that weight
 

kheidolph

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The dealers are terrible about knowing what they are supposed to do. There is a technical bulletin that was released by Mopar back in February 2018. I've attached it here. Take this to your dealer and show it to them. They will then know what they have to do. Cost should be between $125 and $200 depending on how nice your dealer is. Some will do it for free if you've been in there frequently. Also, my dealer only has one technician that can do this on Wednesdays only. So getting a properly trained individual might be part of the challenge. @Freddiejeep I hope this helps you get taken care of.

Regarding recalibration. Recalibration doesn't necessarily improve your gas mileage. It will adjust the computer which will then adjust your shift points which "may" help with MPG but probably not by much. However, it does change the INDICATED MPG (as well as speed) which are just calculations. This is because the computer really only counts axle rotations and fuel consumption. This means that you will drive farther on larger tires with the same number of axle rotations.

For example:
Let's say that you have 35" tires and your computer is calibrated for 33" tires.

You travel 20 miles (indicated on your odometer) and it uses 1 gallon of gas. Your indicated MPG would be 20 MPG. Also, in that time your computer thinks you had about 12223 axle rotations [(20 miles x 63360 inches/mile) / (33" x π) = 12223 axle rotations]

However, you are actually driving on 35" tires, this means your 12223 axle rotations yielded 21.2 miles in the real world [12223 rotations x (35 x π) / 63360 inches/mile) = 21.2 miles]

So your actual gas mileage is 21.2 MPG which is about 6% better. So, while this won't really change how much gas it takes to get to work, you will at least "feel" better about it.

This all applies in the same way for your speedometer and odometer as well.

*Please note that when you move to larger tires it doesn't just mean that your MPG improves. Just the calculations change. Due to the unforgiving laws of physics, things like additional weight, rotational inertia, etc, etc...will likely cause your MPG to be lower than it was before you put on larger tires.

Hope this all helps. Sorry about all of the math.
 

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LLANERO

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Freddiejeep

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Update - got the wheels and tires ;) - Speedo def not self adjusting lol
 

yell03

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Is this true? Does calibrating Speedo really improve mpg and get you in 8th gear on the highway?
I just got back from a 110 mile trip each way.
On the way there while driving 55-65 mph it would go in to 8th and get 17-19mpg, before the recal it would stay in 7th and get 13-14mpg at those speeds.

On the way home I was flying at 70-75mph, mpg dropped to 14.8mpg, 8th gear only helps so much when pushing a barn door through the air.
 
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Freddiejeep

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Thought you guys might find this useful - called the dealer they said “the speedo calibration is no longer offered to us....Jeep took that away recently” .......uhhh
 
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Freddiejeep

Freddiejeep

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The dealers are terrible about knowing what they are supposed to do. There is a technical bulletin that was released by Mopar back in February 2018. I've attached it here. Take this to your dealer and show it to them. They will then know what they have to do. Cost should be between $125 and $200 depending on how nice your dealer is. Some will do it for free if you've been in there frequently. Also, my dealer only has one technician that can do this on Wednesdays only. So getting a properly trained individual might be part of the challenge. @Freddiejeep I hope this helps you get taken care of.

Regarding recalibration. Recalibration doesn't necessarily improve your gas mileage. It will adjust the computer which will then adjust your shift points which "may" help with MPG but probably not by much. However, it does change the INDICATED MPG (as well as speed) which are just calculations. This is because the computer really only counts axle rotations and fuel consumption. This means that you will drive farther on larger tires with the same number of axle rotations.

For example:
Let's say that you have 35" tires and your computer is calibrated for 33" tires.

You travel 20 miles (indicated on your odometer) and it uses 1 gallon of gas. Your indicated MPG would be 20 MPG. Also, in that time your computer thinks you had about 12223 axle rotations [(20 miles x 63360 inches/mile) / (33" x π) = 12223 axle rotations]

However, you are actually driving on 35" tires, this means your 12223 axle rotations yielded 21.2 miles in the real world [12223 rotations x (35 x π) / 63360 inches/mile) = 21.2 miles]

So your actual gas mileage is 21.2 MPG which is about 6% better. So, while this won't really change how much gas it takes to get to work, you will at least "feel" better about it.

This all applies in the same way for your speedometer and odometer as well.

*Please note that when you move to larger tires it doesn't just mean that your MPG improves. Just the calculations change. Due to the unforgiving laws of physics, things like additional weight, rotational inertia, etc, etc...will likely cause your MPG to be lower than it was before you put on larger tires.

Hope this all helps. Sorry about all of the math.

Thanks for taking the time to write this!
 

kheidolph

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Thought you guys might find this useful - called the dealer they said “the speedo calibration is no longer offered to us....Jeep took that away recently” .......uhhh
I'm scheduled to take my wife's JL Sport in next week. I'll let you know if there is a problem or other information I can provide to help you get your calibration done.
 
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