What speedo gear do I need?

[Jason94sport]

31's with 3.27's. I want to correct my speedo. What gear do I need for the speed sensor? Anyone have a part #? The Ford part guys was clueless, & no help at all. All they could give me was the stock part for my year & axle code.

 

[Maniak]

Time to do a little math...

You had 28" tall tires (235x75r15) and now have 31" tires.. 31" tires are 10% bigger.. Soo, you speedo is reading 10% slow right now...

If I am not confusing myself again you want to make the driven gear (the one on the end of the cable) smaller by 10%..

soo.. If you if have a 19 tooth gear in there now you want a 17 tooth.. That will get you close to stock.

~Mark

 

[ma96782]

Here is something to THINK about.

http://www.explorer4x4.com/speedo.html

Aloha, Mark

 

[Jason94sport]

Yeah I saw that, doesn't have 3.27's. I have to check & see how many teeth I have now.
I put my sizes in a calculator & came up with a 6.78% difference.

So If I have this right I need to get a speedo gear that is 6.78% smaller then the one in there. That's 1 tooth less, I guess.

Is that right?

 

[Maniak]

Correct.. You need to speed up your speedo, which means you put on a smaller speedo gear.. and yes you want a speedo gear that will speed it up about 6%.

If your at a 19 tooth now, you will go to an 18 tooth.. which is about 5% difference. You will still be 1% or so off, but thats about as good as you can get (and as accurate as mechanical speedos are you won't notice the difference)

~Mark

 

[Jason94sport]

I just looked. What a nightmare this is going to be. One turn of the 11mm socket & the damn bolt broke in half. Half of it is stuck in the hole. :whyme:

Anyway I only have a 17 tooth gear so I guess I need a 16 tooth one. Going to be fun trying to explain this to the dumb ass parts guys at ford.

 

[Maniak]

If they can't figure it out, post a message.. someone here can get you the p/n..

Heck, I'll be at a ford dealer tomorrow and get the p/n there (I won't buy from them.. them are 50-100% higher than fastpartsnetwork.com and other dealers that sell online)

~Mark

 

[410Fortune]

Maybe I am wrong here but I seem to remember going up in tooth count to compenstate for larger tires.
I am running the 20 tooth speedo gear with 4.10's and 33" AT tires.
It is not even close to accurate (compared to my GPS) but it is as close as I could get, the 21 tooth was too much correction.

You should be able to get your speed sensor out now that the bolt broke. Then you can remove the rest of the bolt with vice grips hopefully.

Ouch!

 

[ma96782]

I told Gene that I had a 19-tooth speedo gear. He didn’t ask what vehicle or gear ratio or even tire size that I had. I then told Gene that when my speedometer was reading 70 MPH I was actually going 65 MPH.

This one was very easy for Gene. He said that to slow down the speedometer 5 MPH we wanted to add one tooth to the gear. Very simple.

From the post above.......you need to ADD a tooth, to slow down the speedometer.....(this example was for BIGGER tires AND lower gears he installed).

__________________________________
__________________________________


So, getting a gear with one LESS tooth......it will spin faster (speed up the speedometer).........to compensate for the bigger tire size (no gear change).

ADVICE:

Next time you see a cop on the side of the road w/ a radar gun.........ask him to help you out.....in the interest of science or public relations.....explain to him your problem.......he'll more than likely agree.....after all, you want to get your speedometer FIXED so you DON'T speed. The cop will also enjoy his day too.....helping you out in the name of science and public relations.

Travel through his trap zone at the recommended speed (steady now).......he'll tell you what you ACTUALLY clocked at (MPH)......then take that information down to the dealership. Speedometer says _____ MPH, cop's radar said it was actually _____ MPH.

OR

Go to a shop that calibrates speedometers (ask the cop where his vehicle is calibrated at).

Aloha, Mark

PS.....Please make the arrangements with him BEFORE you go SPEEDING through his radar trap.

 

[Jason94sport]

Cops won't do that here. They are too busy, & might even give me a fix it ticket for the speedo not working correctly.

I contacted fastpartsnetwork.com. They claim to have one. They weren't cheap at $16. The part was only $6 but shipping, handling, plus tax(they are in FL) adds up.

 

[ma96782]

Sorry to hear that the cops down there are so hard nose.

Aldive's son carries a badge.......

Aloha, Mark

 

[Jason94sport]

I was able to change it out. Finding the correct part was really hard.
After some online researching, I was able to find the correct gear at a local dealer.

It was stated as wine in color(more like purple) Cost me $8.

Fastpartsnetwork.com didn't send me the right gear. So now I'm tring to get a refund from them without the restocking fee since they gave me the wrong info on the part.

 

[Creager]

i had a 16 tooth stock (3.27 gearing)

i have a 19 tooth in there now, its over by ~3% (4.56 gearing and 32" tires)

33"S will probably level me out almost perfect.

The dealership was selling them in packs of two, for $5. You just gotta be careful, ford used 'reverse cut' speedo gears on some models.

 

[MartyD]

I have a '96 Sport 4x4 with 3.73 gears. I went from The stock 235x75r15's to 31x10.5x15's. Is there anyway to know what speedo gear would have come stock so I know which gear to replace it with? (without removing the gear and counting the teeth). The 10% off figure seems about right, my wife was following me on the interstate and when my speedo read around 70 she said I was doing about 77. So if I have read correctly I would want 2 teeth LESS than what I have now, correct?

 

[Jason94sport]

Since your's is a 96 & OBDII, I'm not sure if you can correct it with a speedo gear. I think it's ECU controlled on 95+

Might want to ask about that.

And taking it out is the only way to check how many teeth you have.

 

[justanother1]

I'm not trying to steal the thread but I have just taken off P235/75/R15 tires and installed 31x10.50x15 tires on our 96 thta has 3.73 gears from factory. Our doot tag shows P225/70/R15 as the original tire size. Our speedo gear is black with 20 teeth. According to the calculations that I have done, I need a 18 tooth gear unless I can correct the speedo through the ECU. It would be great if someone knows if the ECU control the speedo.

 

[HappyGilmore]

From the post above.......you need to ADD a tooth, to slow down the speedometer.....(this example was for BIGGER tires AND lower gears he installed).

__________________________________
__________________________________


So, getting a gear with one LESS tooth......it will spin faster (speed up the speedometer).........to compensate for the bigger tire size (no gear change).

ADVICE:

Next time you see a cop on the side of the road w/ a radar gun.........ask him to help you out.....in the interest of science or public relations.....explain to him your problem.......he'll more than likely agree.....after all, you want to get your speedometer FIXED so you DON'T speed. The cop will also enjoy his day too.....helping you out in the name of science and public relations.

Travel through his trap zone at the recommended speed (steady now).......he'll tell you what you ACTUALLY clocked at (MPH)......then take that information down to the dealership. Speedometer says _____ MPH, cop's radar said it was actually _____ MPH.

OR

Go to a shop that calibrates speedometers (ask the cop where his vehicle is calibrated at).

Aloha, Mark

PS.....Please make the arrangements with him BEFORE you go SPEEDING through his radar trap.

thank you. this post was a tremendous help along with the rest of the thread.

 

[pitbulldell]

Anyone got any updates on correcting your speedo gear since this post was started back in 2006? I want to put 275/50/20 on my 95 ex and will need to correct the speedo

 

[detwingsfan16]

i have a 97 ranger 2wd and i fixed my issue from bigger tires with a gear...i would think the explorer is the same...1998 was the body change for rangers so i think that is when it went to ecu