Best speedo correction approach for larger tires

[owyheerat]

Finally over the "15" hump!...

'99 Gen3 Base model 2WD 4cyl. Auto...

After purchasing this truck my first priority was new tires. Just a city / highway truck, no offroading. What I immediately encountered was similar to my experience with a recently restored '92 Celica Convertible...very limited choice in the original tire size of 225/75/15. Also, the 15" rims on the truck were rather shabby looking, missing two caps. I liked the look of the stock 16" rims and was fortunate to find a set at a local boneyard which I acquired and am in the process of repainting. Got a great deal on some stock size 265/70/16's from Tire Rack. Now I must deal with correcting the speedo...the larger tires as most of you will know throw it off by about 8mph on the plus side.

Yes, I have already researched this, here and elsewhere but many of the references I came across were rather old. So I'm looking for fresh input and first hand experiences...what I hope for is the most practical, most accurate, easiest to install. I have seen and read about the SpeedoHealer and Yellow Box. But if this vehicle had an option of 16" tires wouldn't there be a way to re-gear it? I would really prefer to get this accomplished without yanking the dash / kickpanels apart if possible. Really need to get going on this ASAP due to it being January...I live in Ohio...and the tires on the truck are in no way Winter worthy. Supposed to be 68 degrees tomorrow...but that sure ain't gonna last long. Very much appreciate any and all help and info for this issue...

I have a 99 base model non abs, and I jumped from stock 225's to 35's plus regeared. My speedo and odo were way off.
Official home page of the Yellow Box Speedo Recalibrator This is what I used and am very glad I did . Super easy install and easy to adjust to get speedo / odo exact. I ordered the plug and play version, and it was exactly that. I've been using it for 3 years, no issues.

Durwin

 

[trackntrail]

Just get a scan gauge. You can plug in your speedo correction % and it will display the correct speed. It also lets you monitor coolant temp, trans temp (99+), voltage, etc.

 

[4Tuitous]

Getting closer...maybe...

To all of you who have responded, my great thanks...
I believe I am closer to the simplest, least expensive, least hassle solution...not sure though. A recap here, with new info...

First, my vehicle: '99 Base model, 4cyl. Auto - NON-ABS - electronic speedo.
Original tires 225/75/15 - NOW riding on 265/70/16 (optional stock size).
Speedometer reading now LESS than actual speed...about 5mph @ 60mph.

Second...regarding some of the solutions offered, all of which I appreciate for your experience and time. My use for this truck is a simple daily driver...period.
I do not have nor want a GPS, do not intend to buy any additional gauge which I assume from photos has to be attached somewhere to the dash, and I have no intention of swapping diff. gears. Just want an accurate speedo...

I spent some time at a Yota dealer's shop with whom I have a good relationship. Fortunately for me, a slow day so I did get some useful info. The speedo sensor for my truck is fairly common across many T4R variants...primary part # is 83181-12020. On my truck, located on driver's side of the tranny, very easy access. The "driven gear" as they identify it is quite easy to replace, a simple retainer clip...and they usually come with a new oil seal as well. My guy at the shop had a few conversations with a tech who wasn't too busy...and after about twenty minutes, he came across a notation on one of these gears which specified "for 16" tires". Part # 33403-39415. Ah, success!...I thought...but came home to do some last verification before purchasing something I can't return. Now, not so sure, somewhat confused...

I came across a webpage called "Adventure Taco"...obviously an avid off-roader but also a serious numbers nerd...wow. What a load of info. But he did have a LOT of relevant stuff on there, including some other driven gear specs, and now this is what confuses me. All these driven gears identify as 33403-( ), with the second set of numbers designating tooth count. The 39415 variant is 33 tooth, the largest they make. But if my speedo is reading SLOWER than my actual speed...wouldn't a larger, more teeth gear make it WORSE? There are two other variations specified for auto trans., one 32 teeth and one 30. I do not know what is currently in my truck. Only way to know would be take it out and count 'em. Not going to buy anything until I get this sorted out. Still hoping this might be my easy fix...if not I'll have to go the SpeedoHealer route I guess. Hoping some of you who have commented are following this thread...anybody?

 

[Bad Luck]

First, my vehicle: '99 Base model, 4cyl. Auto - NON-ABS - electronic speedo.
Original tires 225/75/15 - NOW riding on 265/70/16 (optional stock size).
Speedometer reading now LESS than actual speed...about 5mph @ 60mph.

I'm not sure why you thought it would be the other way around. A larger than stock tire goes further per rotation compared to a stock tire.

I came across a webpage called "Adventure Taco"...obviously an avid off-roader but also a serious numbers nerd...wow. What a load of info. But he did have a LOT of relevant stuff on there, including some other driven gear specs, and now this is what confuses me. All these driven gears identify as 33403-( ), with the second set of numbers designating tooth count. The 39415 variant is 33 tooth, the largest they make. But if my speedo is reading SLOWER than my actual speed...wouldn't a larger, more teeth gear make it WORSE? There are two other variations specified for auto trans., one 32 teeth and one 30. I do not know what is currently in my truck. Only way to know would be take it out and count 'em. Not going to buy anything until I get this sorted out. Still hoping this might be my easy fix...if not I'll have to go the SpeedoHealer route I guess. Hoping some of you who have commented are following this thread...anybody?

If you are wanting to correct it with a speedo gear change you will need to know what your current tooth count is. You will want a smaller new gear (less teeth) than the current gear so that it will spin faster. The person on Adventure Taco probably regeared in addition to larger tires and needed to correct for a speedometer faster than gps speed.

 

[4Tuitous]

Yep...you are correct. It's all been a bit confusing but after much research and lots of feedback I now have a better understanding. I still may end up going the Dakota Digital route but I'll at least take this path to conclusion. Seems the only way to know is to remove the speedo sensor and count gear teeth. Just curious...since I know absolutely zero about the internal workings of automatic transmissions...do you have any knowledge about how the drive / driven gear for the speedo sensor engage? Concerned that a smaller, fewer tooth driven gear on the sensor might not properly connect with the drive gear. Was wondering if perhaps they only engage when tranny is placed in "D". Appreciate your response...

 

[Iffykid]

Finally over the "15" hump!...

'99 Gen3 Base model 2WD 4cyl. Auto...

After purchasing this truck my first priority was new tires. Just a city / highway truck, no offroading. What I immediately encountered was similar to my experience with a recently restored '92 Celica Convertible...very limited choice in the original tire size of 225/75/15. Also, the 15" rims on the truck were rather shabby looking, missing two caps. I liked the look of the stock 16" rims and was fortunate to find a set at a local boneyard which I acquired and am in the process of repainting. Got a great deal on some stock size 265/70/16's from Tire Rack. Now I must deal with correcting the speedo...the larger tires as most of you will know throw it off by about 8mph on the plus side.

Yes, I have already researched this, here and elsewhere but many of the references I came across were rather old. So I'm looking for fresh input and first hand experiences...what I hope for is the most practical, most accurate, easiest to install. I have seen and read about the SpeedoHealer and Yellow Box. But if this vehicle had an option of 16" tires wouldn't there be a way to re-gear it? I would really prefer to get this accomplished without yanking the dash / kickpanels apart if possible. Really need to get going on this ASAP due to it being January...I live in Ohio...and the tires on the truck are in no way Winter worthy. Supposed to be 68 degrees tomorrow...but that sure ain't gonna last long. Very much appreciate any and all help and info for this issue...

I would start by getting a GPS reading compared to the speedo and go from there.

Re
On my stock 00 Limited I replaced the stock 265/70/16s with 265/75/16s assuming my speedo was going to be off but not knowing by how much I just checked and my speedo was basically right on the money at 60-65 so evidently my stock speedo was reading faster than actual, My understanding it is quite common for a stock setup to read faster than actual mph on alot of older vehicles.

 

[phattyduck]

To all of you who have responded, my great thanks...
I believe I am closer to the simplest, least expensive, least hassle solution...not sure though. A recap here, with new info...

First, my vehicle: '99 Base model, 4cyl. Auto - NON-ABS - electronic speedo.
Original tires 225/75/15 - NOW riding on 265/70/16 (optional stock size).
Speedometer reading now LESS than actual speed...about 5mph @ 60mph.

Second...regarding some of the solutions offered, all of which I appreciate for your experience and time. My use for this truck is a simple daily driver...period.
I do not have nor want a GPS, do not intend to buy any additional gauge which I assume from photos has to be attached somewhere to the dash, and I have no intention of swapping diff. gears. Just want an accurate speedo...

Swapping the diff is probably the cheapest option if you can do it yourself. You can probably find a free one on here! You'll need to know what your current diff ratio is to know if it truly is going to be cheap though - only the 4.10 gears are cheap (I know what your diff ratio would be if you had the V6 - not sure with the 4 cylinder).

Otherwise, just pop that sensor out and count the teeth and report back.

-Charlie

 

[CWccw]

Guys, he's going from 225/75-15 tires to 265/70-16 tires - it is a fairly large change in rolling diameter (similar to going from stock tires to 35's on the 16" wheel trucks).

Assuming the OP's truck has ABS, the speedo is driven off the ABS system. Re-gearing will have no effect on speedo reading, only tire size has an effect. Re-gearing is a good idea though, and 4.10 rear 3rd members should be easy to find cheap.

I used a Dakota Digital speedometer interface to correct my speedometer. See my thread here: https://www.toyota-4runner.org/2456477-post12.html

There is no plug-in solution for reprogramming the speedo or anything like that (sorry, it isn't a domestic truck...). You will have to wire something in.

-Charlie

Is a early model 98 compatible? I read in another thread the user was working with a 96 and the only way to fix speedo error was to change the gear in the trans. Dealt with similiar issues in the fiero group, they were selling custom sized speedo gears made from a 3d printer. Surely we have someone with these capabilities if thats what it comes to.

 

[talkstometal]

did you ever resolve this issue? I have the same problem now. think that less teeth would be the answer.

 

[heat]

[MENTION=139000]phattyduck[/MENTION] has some kind of black box for this

 

[phattyduck]

[MENTION=139000]phattyduck[/MENTION] has some kind of black box for this

Yeah, I used this: SGI-100BT: Universal Speedometer and Tachometer Interface
(or maybe the previous version?)

Anyway, it goes between the ABS unit and the cluster for ABS trucks, or the speed sensor on the trans and the cluster on non-ABS trucks.

Helpful if you might change things again in the future - all you have to do is update an adjustment factory instead of find new parts.

-Charlie