How to recalibrate your speedometer after changing tire sizes or gears

JeepOnDecision said:
Going from 27" tires to 33s is an increase of 1.222x. The same increase (numerically) in gears would put you at 3.75. You SHOULD have 3.73s in there, or something like that. Someone correct me if I'm wrong
Click to expand...

His problem is he thinks he has 3.07s and 33’s and the chart doesn’t offer a Speedo gear for that. He has made no assumptions that he is regeared and based off the average cheap Jeep owner, he is probably still on 3.07s. Therefore there is no perfect speedo gear for him but a 26 would get it close.
 
Jack it up, spin the tire 1 time. See how many times the driveshaft turns.
Just past 3? 3.07
Almost 4? 3.73
Etc.
Figure what gears you have then go from there
 
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JeepOnDecision said:
Not for 97s, so I've never done anything like that. I be ol' skool
Click to expand...

You can get one if you get the 98-06 speed sensor and splice on the corresponding pigtail which is the same 3 wires and colors. The 97 used an older style speed sensor from the YJ that leaked ATF up into the terminals so for 98 they changed it to a newer/better design. That's the most common connector so that's what all the programmer companies decided to get on board with. It's definitely nice to be able to change the speedo electronically rather than buying a gear every time, especially since Jeep owners typically change their minds (and speedos) a lot.
 
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machoheadgames said:
You can get one if you get the 98-06 speed sensor and splice on the corresponding pigtail which is the same 3 wires and colors. The 97 used an older style speed sensor from the YJ that leaked ATF up into the terminals so for 98 they changed it to a newer/better design. That's the most common connector so that's what all the programmer companies decided to get on board with. It's definitely nice to be able to change the speedo electronically rather than buying a gear every time, especially since Jeep owners typically change their minds (and speedos) a lot.
Click to expand...

OL' SKOOL!!!
OL' SKOOL!!!!!!!!!!!
 
machoheadgames said:
His problem is he thinks he has 3.07s and 33’s and the chart doesn’t offer a Speedo gear for that. He has made no assumptions that he is regeared and based off the average cheap Jeep owner, he is probably still on 3.07s. Therefore there is no perfect speedo gear for him but a 26 would get it close.
Click to expand...

Correct. I confirmed with GPS when I’m actually going 50mph, Speedo says 45.
 
Chris said:
If you have a 97-06 Wrangler TJ and recently went to bigger tires, you'll probably notice that your speedometer is off. This is an easy fix by purchasing the correct gear for your tire size and ring and pinion.

NOTE: This will not work on 03-06 Rubicon models. See the bottom of this post for more details on what to do if you have a Rubicon.

Here's a chart to help you determine the correct speedometer gear:

View attachment 13277

The speedo gear swap/change takes a mere 5 minutes and only one wrench. This is an easy job that anyone can do.

Item's needed:
  • 1/2'' wrench (socket works too).
  • Some paper towels or rag. (you will drip a bit of ATF)
  • Correct speedo gear for your tire size/axle gear ratio.
  • New O-ring for the drive housing. (for $3 at the dealer, change it for cheap insurance)

View attachment 103

Once you have everything ready locate the Speedo Gear drive on the rear output shaft of the transfer case. (easily seen from the rear of the t-case skid)

View attachment 104

First action to take is to remove the electric connector. Push the lock clip out "the red tab" and press on the connector release and pull it off.

View attachment 105

Next step is to remove the 1/2'' bolt and wishbone clamp from the tail housing. Set these to the side.

View attachment 106

Once the clamp is removed you can now remove the drive housing. It will be secured tight in the tail housing..just work it back and forth until it pops out.

View attachment 107

Now it is time to remove the old gear and install the new. To remove the old just grab the gear in one hand and the drive housing in the other...pull. It pops right out with little effort.
Pull the old O-ring off of the drive housing and install the new one.

View attachment 108

Install the new speedo gear by pushing it into the drive sensor housing. Be careful not to pinch the o-ring when installing. (helps if you rub a bit of atf on the o-ring)

NOW...here is a little thing that a lot of people miss. The speedo gear is offset in the sensor housing. This is to adapt to different size gears. And there is 3 clocked position that you can install it. "But how do I do that?" Easy...look on the side of the drive sensor housing.

You will see the numbers....
26-31
32-38
39-45

View attachment 109
This image has been resized. Click this bar to view the full image.
View attachment 111

Simply find where your speedo gear tooth number falls. When you install the unit into the rear tail housing point the number that your gear fall in down at the 5 o'clock position of the hole. Press the gear into the tailshaft.

View attachment 112

Install the wishbone clamp and bolt to secure the drive sensor housing. DO NOT OVER TIGHTEN the bolt. The tail housing is aluminum. Just snug it down good. Don't crank on it.
Besure you set the clamp teeth into the cuts in the drive housing.

View attachment 113

Plug the electric connector back in and you are done.

Here you will see the position that your speedo gear tooth count should be angled down. And a completed install. The installed speedo gear in this application was a 41 tooth gear...so 39-45 is down at the 5 o'clock position of the hole.

View attachment 114


How to Correct the Speedometer on Rubicon Models
This above speedometer gear change not work on 03-06 Rubicon models. The speedometer on these is electronically controlled and therefore you only have two options:

1) Some dealers are able to re-program the ECU so that it the speedometer will accommodate for different gearing and larger tires.

2) There are several electronic speedometer calibrators out there, but the one I suggest is the Speedo Healer by Blue Monkey. It's 100% plug-and-play, and uses factory style connectors. Note that you can also use one of these speedometer recalibration modules on a non-Rubicon model (as oppose to swapping the speedo gear as outlined above), but I'm not sure why you'd bother wasting the time and money, when swapping the speedometer gear is both cheaper and easier.
Click to expand...

Will be doing this exact thing in November. This is an Excellent guide!
 
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Viking Jeeper said:
Get this and you can get it exactly right. You can program it to within 0.1% of original. On my LJR I went up 13.8% and it is prefect. You can also change the program is you change gears or tire size.

http://shop.12oclocklabs.com/index.php?route=product/product&product_id=59
Click to expand...

Thanks! This was so easy, no wrench turning, took 10 minutes. If I ever change tires, just reprogram. So simple. And by 'reprogram' I mean holding a button and counting. No rocket science degree needed. lol
 
Sheldon96 said:
Thanks! This was so easy, no wrench turning, took 10 minutes. If I ever change tires, just reprogram. So simple. And by 'reprogram' I mean holding a button and counting. No rocket science degree needed. lol
Click to expand...

For a couple of dollars more than a gear I'm not sure why more people dont do it. Ive seen some go through a couple of gears before they get it right.
 
Chris said:
I'll give it a try. I'm assuming it's easier to setup than it sounds?
Click to expand...

I have a 05 TJ Rubicon that I just had 33s and a lift on. I clicked on your link for the ECU calibrator and it came up with SpeedoHealer v4 for motorcycles. Is this the same calibrator that you were referring to? Thank you!
 
JT05TJ said:
I have a 05 TJ Rubicon that I just had 33s and a lift on. I clicked on your link for the ECU calibrator and it came up with SpeedoHealer v4 for motorcycles. Is this the same calibrator that you were referring to? Thank you!
Click to expand...

Yep, that one works as do many others. The way these things work is pretty simple, there's nothing revolutionary about them really.
 
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12oClockLabs makes a universal speedometer calibrator for $79.99
SpeedoDRD Model: U1 *Universal Kit $79.99
Or with Jeep harness:
SpeedoDRD Model: J1 Jeep Wrangler TJ (1998-2006) $89.99
http://shop.12oclocklabs.com/index.php?route=product/product&path=31&product_id=59
The Universal Kit does require some basic wiring to install. It's fairly easy, and only 4 wires; [positive, ground, signal-in, signal-out]. Universal Kit works for Cars, Trucks, & Motorcycles with digital odometers, and 3 wire speed sensors.
 
Last edited:
Uncle Sam said:
12oClockLabs makes a universal speedometer calibrator for $80.
SpeedoDRD Model: U1 *Universal Kit
http://shop.12oclocklabs.com/index.php?route=product/product&path=31&product_id=59
The Universal Kit does require some basic wiring to install. It's fairly easy, and only 4 wires; [positive, ground, signal-in, signal-out]. Universal Kit works for Cars, Trucks, & Motorcycles with digital odometers, and 3 wire speed sensors.
Click to expand...

Guess Viking Jeeper mentioned them first.
https://wranglertjforum.com/threads...-changing-tire-sizes-or-gears.83/post-1187100
 
Chris said:
If you have a 97-06 Wrangler TJ and recently went to bigger tires, you'll probably notice that your speedometer is off. This is an easy fix by purchasing the correct gear for your tire size and ring and pinion.

NOTE: This will not work on 03-06 Rubicon models. See the bottom of this post for more details on what to do if you have a Rubicon.

Here's a chart to help you determine the correct speedometer gear:

View attachment 13277

The speedo gear swap/change takes a mere 5 minutes and only one wrench. This is an easy job that anyone can do.

Item's needed:
  • 1/2'' wrench (socket works too).
  • Some paper towels or rag. (you will drip a bit of ATF)
  • Correct speedo gear for your tire size/axle gear ratio.
  • New O-ring for the drive housing. (for $3 at the dealer, change it for cheap insurance)

View attachment 103

Once you have everything ready locate the Speedo Gear drive on the rear output shaft of the transfer case. (easily seen from the rear of the t-case skid)

View attachment 104

First action to take is to remove the electric connector. Push the lock clip out "the red tab" and press on the connector release and pull it off.

View attachment 105

Next step is to remove the 1/2'' bolt and wishbone clamp from the tail housing. Set these to the side.

View attachment 106

Once the clamp is removed you can now remove the drive housing. It will be secured tight in the tail housing..just work it back and forth until it pops out.

View attachment 107

Now it is time to remove the old gear and install the new. To remove the old just grab the gear in one hand and the drive housing in the other...pull. It pops right out with little effort.
Pull the old O-ring off of the drive housing and install the new one.

View attachment 108

Install the new speedo gear by pushing it into the drive sensor housing. Be careful not to pinch the o-ring when installing. (helps if you rub a bit of atf on the o-ring)

NOW...here is a little thing that a lot of people miss. The speedo gear is offset in the sensor housing. This is to adapt to different size gears. And there is 3 clocked position that you can install it. "But how do I do that?" Easy...look on the side of the drive sensor housing.

You will see the numbers....
26-31
32-38
39-45

View attachment 109
This image has been resized. Click this bar to view the full image.
View attachment 111

Simply find where your speedo gear tooth number falls. When you install the unit into the rear tail housing point the number that your gear fall in down at the 5 o'clock position of the hole. Press the gear into the tailshaft.

View attachment 112

Install the wishbone clamp and bolt to secure the drive sensor housing. DO NOT OVER TIGHTEN the bolt. The tail housing is aluminum. Just snug it down good. Don't crank on it.
Besure you set the clamp teeth into the cuts in the drive housing.

View attachment 113

Plug the electric connector back in and you are done.

Here you will see the position that your speedo gear tooth count should be angled down. And a completed install. The installed speedo gear in this application was a 41 tooth gear...so 39-45 is down at the 5 o'clock position of the hole.

View attachment 114


How to Correct the Speedometer on Rubicon Models
This above speedometer gear change not work on 03-06 Rubicon models. The speedometer on these is electronically controlled and therefore you only have two options:

1) Some dealers are able to re-program the ECU so that it the speedometer will accommodate for different gearing and larger tires.

2) There are several electronic speedometer calibrators out there, but the one I suggest is the Speedo Healer by Blue Monkey. It's 100% plug-and-play, and uses factory style connectors. Note that you can also use one of these speedometer recalibration modules on a non-Rubicon model (as oppose to swapping the speedo gear as outlined above), but I'm not sure why you'd bother wasting the time and money, when swapping the speedometer gear is both cheaper and easier.
Click to expand...

I have a 2000 TJ 4.0 with 3.73 gears and “33 tires. I purchased a 31 tooth speedo drive gear, but it’s about 5 MPH low at speeds of around 65 MPH.

Can you tell me how to determine a better speedo gear size?
 
I used one of these. Took about 5 minutes to instal, works great. Doesnt matter tire size or gear ratio. Drive 60mph (I found one of those digital speeding signs on the highway) enter what your actual spedo says and it does all the math for you. Couldn't have been much easier. If you change tire size again later, do it again
https://www.polyperformance.com/hea...uqtfsAAUPDFQ9WLk571MxH8a3BP-j2UIaAjubEALw_wcB
 
AWTJ2000 said:
I have a 2000 TJ 4.0 with 3.73 gears and “33 tires. I purchased a 31 tooth Speedo drive gear, but it’s about 5 MPH off at speeds of around 65 MPH.

Can anyone tell me how to pick a more exact fit/part to correct the speedo?
Click to expand...

Is it reading faster than GPS or slower?
 
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