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Replacing the Speedo Gear

February 21, 2018.

How many miles do you have on your truck? If you're anything like me, you'll answer this by looking at your odometer, reading a number, and concluding that you have that many miles - 83,078 miles in my case.

Like me, you're wrong.

Your odometer is lying to you. And so is your speedometer. I covered why that is here - go read it. I'll wait. Speedometers, Odometers, and Gas Mileage – All Lies!

OK, welcome back. Or not if you're like me and just skipped over that last link. Let me try to recap:

The reading from your speedometer and odometer are affected by lots of things - like tire size, differential gear ratio, and more. Because of this, car manufacturers make a "best effort" to get the speedometer to be "close" (usually a little bit fast) in a stock configuration. Unfortunately, I'm no longer running a stock truck and the 33" tires and 4.88 differential gears have resulted in my speedometer reading 80 mph when I'm actually doing 69 mph.

All that means that I don't actually have 83,078 miles on my truck. I've actually got about 75,000 miles on it. Not that I'm planning to sell it any time soon ever. But as much as I want to hit the 500,000-mile club, I would rather that my odometer be correct - or at least as close as possible.

To that end, I ordered the largest speedometer gear they make for a 2000 Toyota Tacoma - the 33-tooth model - to replace the 30-tooth model that was installed in the factory.

It arrived, along with a new gasket and clip and I promptly set it aside while @mrs.turbodb and I drove several thousand miles down, through, and back from Death Valley.

It was an epic trip. Don't miss reading about it here: Death Valley (Jan 2018).

Now, several weeks later, it's time to install that gear, and hope that my speedometer reads slower than I'm actually going, and my odometer logs fewer miles than I've actually gone. You know, so the resale value of the truck is higher.

The first step was to remove the skid plates, since the speedometer gear housing is attached to the transfer case, which is well-protected by the @relentlessfab mid-skid. Six bolts and a floor jack, and I lowered the skid to find about 5 lbs of Montana, Wyoming, and a bit of Utah dirt that had hitched a ride back from The De-Tour (another epic adventure you shouldn't miss).

The speedometer gear housing is secured to the transfer case with a single 10mm hex bolt, which was easily removed after I disconnected the plug for the sensor.

With the bolt removed, the housing can be pulled out of the transfer case easily (if the o-ring hasn't degraded) and mine came out with a rewarding sucking sound, along with a few teaspoons of oil.

Fingers crossed that losing a bit of oil isn't the end of the world here. At this point, pop out the spring clamp, and pull the old gear out of the housing. Again, you'll get a nice sucking sound as it comes out. It was rewarding enough that I did it a couple times.

In order to fit more teeth (thus rotating more slowly to bring the mph and odometer readings down), the new 33-tooth gear has to have a larger diameter than the old 30-tooth gear - which it clearly does.

As a bonus, it's also painted bright pink. And we all know, most ladies like pink. So if you install one of these, it's more reason for them to like your truck.

The new gear slides right into the housing and is secured with the newly supplied clip. I also replaced the o-ring, though my original still seemed just fine, and was ready to re-install the housing assembly.

Installation is simply the reverse of removal, and I found that the machining tolerances of the hole in the transfer case, and the speedometer gear housing were so close that it helped to wipe a bit of oil on the housing in order to get it to slide in (with a few gentle taps).

I then re-attached the bolt ("tight") and plugged in the sensor.

And then it was the moment of truth. Would my speedometer (and odometer) be accurate? There was only one way to find out - I started up the truck and headed out to I-5 to compare my GPS speed with my speedometer.

Alas, it wasn't correct - but it was a lot closer. It now reads about 6% high (instead of 14%), which matches what the truck originally shipped with from the factory.

So - at least on my truck, the following configurations result in nearly identical speedometer/odometer margins of error (~6%):

And, other configs I've run:

  • ~0% error
    • 255/85 R16 BFG KM2 tires + 4.10 gear ratio + 30-tooth speedometer gear
  • ~14% error
    • 255/85 R16 BFG KM2 tires + 4.88 gear ratio + 30-tooth speedometer gear
    • 255/85 R16 Cooper ST Maxx tires + 4.88 gear ratio + 30-tooth speedometer gear


So yeah, my odometer still lies, but I don't really care. Because it just makes the adventure "longer."


  1. Andrew
    Andrew November 29, 2018

    Damn glad I found this. I did a 4WD conversion on my 04 double cab prerunner this month. I used a 4Runner transfer case that did not use the speed sensor hole to determine speed so it was plugged. I popped a 33 tooth gear in and it's been a little slow. It will read 31 when I"m going 38. Hopefully going down to a 30 will fix it.

    • turbodb
      turbodb November 29, 2018

      Glad you found it too - hope that speedo gear works for you. IMO though, being a bit slow is better than a bit fast...means you're racking up ODO miles more slowly too, hahahahaha!

      • Andrew
        Andrew December 10, 2018

        30 tooth gear count was perfect for my 265/75/16 tires + 4:10 geared truck. Maybe about half a mph off. Thanks again.

    • Justin v
      Justin v May 13, 2020

      I cannot get mine to work I did the same swap but in an 03 prerunner. Got the trans and tcase from a 98 4runner. And my speedo doesn’t work. Bought a new sensor from the dealer hopefully that will work. If you have any pointer please let me know. Bought a 98 Tacoma tcase speed sensor.

      • turbodb
        turbodb May 13, 2020

        Bummer to hear that your Speedo isn't working. I guess I wouldn't really expect a different Speedo gear to fix the problem if you weren't getting any reading at all... hope you get that sorted though, and reply here when you do!

    • Mic
      Mic December 19, 2022

      Hello and I hope you're having a good day.
      I am interested in doing a speedo gear in my 97 Tacoma. but it does not have an electronic Speedo it has a cabled Speedo. Do you know of a part that would work in this case?

      • turbodb
        turbodb December 21, 2022

        Hey Mic, unfortunately, I'm not familiar with the speedo gear setup on the cabled speedo. What I'd do in that situation is head down to a dealer and tell them that you need a new speedo gear, then, ask them about the variants they have. Hopefully they'll have one with more teeth that will fit (I'd just always go straight for the one with as many teeth as possible...because even then, it's not always enough, hahaha!

  2. Justin v
    Justin v May 14, 2020

    I tested the sensor by hand and speedometer works. But when I plug it in it must not reach the gear to make the sensor move. Not sure what is going on here. Thinking of buying a bigger gear and if it works buy the other part to adjust the speedo.

    • turbodb
      turbodb May 14, 2020

      I guess I'm a bit confused then... Does the speedo work when the original speedo gear is in the transfer case? If it does, are the two shafts the same length, and did the new gear seem to seat fully?

      Dakota digital is definitely another way to go; more configurable as well.

      • Justin v
        Justin v May 15, 2020

        Update! The larger gear was the fix! The 30 gear was not large enough and was not reaching the shaft gear. Went with a 33 gear and works now. Speedo works but might be off a little. That is Fixable with Dakota digital.

        • turbodb
          turbodb May 15, 2020

          Awesome, glad you got it sorted!

  3. Alex G
    Alex G June 26, 2020

    I tried this to fix my speedometer after going to 4:88's and 33"s, but ended up breaking the 33 tooth gear after 8 miles. The speedometer was within 2% of the right speed going from a 30:11 gear to a 33:11. The 33 tooth gear was too big and had been ground loose from the shaft.

    • turbodb
      turbodb June 26, 2020

      Bummer Alex!

      Strange that it was able to fit in, seemed to be "correct" from a speed perspective, and lasted for 8 miles (that's a lot of spinning for a gear that small)...I wonder if something else was going on - bum part or something. What transmission, t-case, and year is your Tacoma? Might be a good reason to go with the Dakota Digital - seems like a more tunable system anyway.

  4. Lou
    Lou July 22, 2020

    Just read this article after searching high and low. Do you know if this will work on a 1st gen Tundra? I have a 2006 Tundra and after re-gearing and bigger tires, my speedometer is off.


    • turbodb
      turbodb July 23, 2020

      Hi Lou, to tell you the truth, I'm not sure about a first-gen Tundra. Maybe someone else can pipe in with the info here.

  5. Jay Merry
    Jay Merry January 8, 2021

    I’ve done a 4.10 to 4.88 swap on my Tacoma with 32” tires. It’s an auto, and the speed now seems to register about 10mph faster than actual. Any thoughts on a Speedo gear swap? Would the 33t work or should I look at a larger? Also, which supplier did you use?

    • turbodb
      turbodb January 8, 2021

      Hi Jay, Even with a 33 tooth speedo gear (that's the largest available, to my knowledge), you're still going to register several MPH faster than you're actually going, with 4.88s and 32s. Instead of doing the speedo gear, I'd go with a Dakota Digital SGI-100BT Universal Speedo instead. It's an electronic solution that will allow you to infinitely tune your speedo - so if you ever change tire size, etc. in the future, you can just update the device and get the correct reading again.

      • Jay Merry
        Jay Merry January 9, 2021

        Thanks so much. It’s more expensive, but sounds like the better solution. Any idea how difficult the installation is? Compatible with a first gen Tacoma?

        • turbodb
          turbodb January 9, 2021

          Definitely compatible with a 1st gen. Not sure about the install - but I'm sure they have instructions that you could download and get a sense of it prior to tackling the project ?.

  6. Larry
    Larry October 12, 2021

    I have 265/70/17 tires and recently installed 4.56 gears. This 33 tooth gear made my speedo spot on again! Super easy install. It is a little snug going back in, as the write up says. I just oiled up the gear and o ring and gave it a few taps.

    • turbodb
      turbodb October 12, 2021

      Awesome, glad this worked for you Larry! Would love a Google review if you have a few minutes. Helps others find the content as well!

  7. Stinkyspice
    Stinkyspice November 12, 2022

    I just got 5.29 and I run 285/55/16 on my 2003 Tacoma. 3.4 4wd. Would the 33 tooth gear get my spedo closer?

    • turbodb
      turbodb November 12, 2022

      I'm assuming you're running 255/85R16 (essentially 33's) since I don't think there is a 285/55 tire size. The 33 tooth gear will get your speedo closer to correct, but it still won't really be all that close - you'll still seem to be going 10+mph faster than you actually are.

      The better solution would be to install a Dakota Digital SGI-100BT Universal Speedo... or even better, a LutzAuto Toyota 3 Wire Speed Sensor Calibrator/Correction Device. That will allow you to have infinite adjustability to work with any gears/tire size you might have in the future.

    • turbodb
      turbodb January 4, 2023

      Nice! Always good to hear about more products that solve this problem. I recently picked up a LutzAuto Toyota 3 Wire Speed Sensor Calibrator but haven't had a chance to install it yet. Being that it's plug and play and seems to have really simple calibration, I'm hoping that it'll be easier than the jumper setup of the Dakota Digital and Yellow Box, but any of them are better than the "stock" setup!

      • Sam Kupiec
        Sam Kupiec February 13, 2023

        Any update on whether or not you have installed the LutzAuto unit on your rig? I asked because I saw on the website the following:
        Disclaimer: This product is to be used offroad only. Lutz Auto is not responsible for miscalibration or malfunction of any speedometer.
        Seems like a great option to avoid swapping out the speedometer gear, but I'm wondering what drives the disclaimer to limit the device for off-road use only. I upgraded to 255/85/R16 with my stock 4.10 gears and my speedometer has been off by about 5% with my speedometer (reading 62mph when going 65 on the highway).

        • turbodb
          turbodb February 13, 2023

          Hey Sam, I haven't installed mine yet - life has just been too busy, and I still need to drop the transfer case again to fix the seal, so I was going to do it at the same time. The reason for the disclaimer is simply a liability one. I haven't verified explicitly, but since you're messing with the speed, I'm sure he doesn't want to be liable for any tickets or running out of gas because the ODO readings are off - that kind of thing. It's sort of like how all the aftermarket bumpers, lights, etc. are also only rated for off-road use, and while they are obviously stronger, don't give any tow ratings, etc. Anyway, I'd not worry about it at all; I think it's a great solution. ?

          • Sam Kupiec
            Sam Kupiec February 13, 2023

            Awesome, I appreciate your input on that! I have an UltraGauge to closer monitor fuel status and typically will have Google Maps up showing real-time GPS speed. I really like the looks of the LutzAuto module because of its plug-and-play capability. I'm sure dialing it in will take some effort, but it sounds like they provide some guidance to regarding starting point calibrations). I can report back once I install it and have it working on my truck!

            • Sam Kupiec
              Sam Kupiec March 13, 2023

              Besides the oil grime on my transfer case (possibly my leaky valve covers), the installation of the LutzAuto module was very straightforward. Going from 265/75/R16 to 255/85/R16, I went up 5.5% (11 presses in the positive direction on the speedometer calibrator) and I'm now spot on. Great and simple fix that avoids messing around with guessing at the number of teeth for a speedometer gear!

              • turbodb
                turbodb March 15, 2023

                Awesome, thanks for the update Sam! I still haven't installed mine yet, but I hope to get it taken care of in the next month or so; I've got several niggling litle things that need taking care of, and I want to get them all done at the same time.

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