where is the speedometer sensor on my sport trac!

HEY ALL,

my speedo has been off since i moved up to 33" tires. it is off by about 3-5 mph, so after doing some searching on the forum, i read about the little 19 tooth gear sensor located on the top of the rear diff and switching it to a 20 tooth gear.so i went to my local ford dealer and they said the same thing. so i got me a 20 tooth speedo sensor, for 6 bucks. im a little unclear and unsure about where to find it now that im under the truck.

this is what the new speedo sensor that i bought looks like:



this is what i found at the top of my diff:



after removing this little piece from the top of the diff, this is what it looks like in the light:


they look a little similar, but there just doesnt seem like they are any way the same part.

i have a 2003 sport trac XLT 2WD automatic, does anyone out there know exactly where i need to look to find and replace this speedometer gear? what is it exactly that i pulled from the top of the diff? has anyone with the same vehicle done this mod before? any help with this would be awesome. thanks fellas, i know someone out there will have knowledge.

ok, so ive read stuff on the net about the speedometer sensor also doubling as my abs sensore which conflicts with what the ford dealership told me. the ford dealership told me that the sensor on top of the diff was the speedo, and the abs sensors are located right by the rear calipers. well, i havent been able to find any sensor of any kind near the calipers and and when i looked up the little part that i detached from the top of the rear diff, i have found parts dealers that refer to it as a abs/speedo sensor.

so if the little greasy piece that i pulled out of the top of the diff (pictured above) performs both functions, and the 20 tooth gear that i bought for 6 bucks is not compatible with my explorer, than i am assuming i need to get someone to recalibrate my speedo and abs sensor electronically?

can any wheel shop or auto place recalibrate my speedo electronically or will i have to go straight to the dealership? i really dont want to go to the dealer being that they not only charge up the rear, but i dont really trust my local dealer already being that they sold me a part that doesnt even work on my explorer.

i have heard of the ultragauge being able to allow you to recalibrate your speedo. is this true? because if it is, would it be a better move to just by an ultragauge for 60 bucks instead of paying probably much mroe than that to get a shop to do it?

please advise!!!

stealerships are stupid, they dont know anything. for your trac that 20tooth gear they sold you has to go back were you bought it it wont work, the speedo is read through the abs and can only be changes with a tuner or ford can do it for around $100 with there expensive machine. even though it would only take a few mins to program. as far as the scan guage i dont think it will do anything for you

so can any mechanic do it or can only ford do it? i have a buddy who owns his own shop, im sure he would do it for me for free if he had the right programming equipment. will ford be the only ones who could do it? thanks for the info and clarification.

sure the shop can do it if he had the right machine, and its unlikely he has the NGK machine(i think that what its called) the only reason i say ford is cause probably 95 percent of shops cant afford this machine. if you do a search on here the are a few threads about this subject

that item pictured is your rear differential abs sensor .

if you went in and asked for a speedometer gear then thats what they gave you .and that would be inside your transmission.

i initially didnt ask them for a speedo gear, i told them what year X i had and that it was a sport trac, told them i had a problem with the speedo being off and the abs light being on. they told me that i could fix the speedo problem with the little 20 tooth gear they sold me for like 6 bucks. then i was told that the abs sensors were mounted near each rear brake caliper and that i would need to get it inspected, but that the speedo adjustment might fix it.

where exactly on my tranny should i be looking to find where this 20 tooth gear goes if in fact it does fit on my tranny? any help would be awesome. thanks.

i have given all the info you need 01 and up x's are abs controlled take the part back and tell them there f*ckin stupid and get another job

ramren16 said:

i have given all the info you need 01 and up x's are abs controlled take the part back and tell them there f*ckin stupid and get another job

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thanks for the info ramren, i have already made plans to take my ST to my friend who owns a shop in the morning. he says he might be able to reprogram it.

i was just responding to joe doe because i didnt ask them at first for a 20 tooth gear, thats just what they gave me.

Vehicle Speed Signal

The vehicle speed signal is generated by the transmission output shaft sensor (OSS) and sent to the PCM. The PCM sends the vehicle speed signal via circuit 679 (GY/BK) to the instrument cluster.


Illustration

I don't recall, is your Trac a 4x4/4x2 and auto or manual trans?

thanks ranchero, like i said, you are a sport trac yoda. mine is an AT 4X2.

so if the transmission output shaft sensor is what produces my speedo readings, then does this 20 tooth gear that was sold to me correspond with this OSS? i still cant figure out where that damn thing goes if it indeed does work with my particular tranny and rig. and if this is the case, then the ABS sensor i found on the top of my diff is strictly an ABS sensor? btw, the illustraion link isnt working for me. could it just be my computer?

well i was under my truck for a good while and i couldnt find where this little 20 tooth gear fits. i looked up my tranny from the door sticker and it's "D", since is a 2003, this is the kind of tranny i have according to the sticky from the transmission sticky

D (1997-2005) ..... A5LDE / 5R44/55E

does anyone know if in fact these trannys use this particular speedo 20 tooth gear? or is the speed computed by the little abs sensor found on the read diff?

much needed bump!

To my knowledge, your speedometer is driven by the VSS in the rear axle (which also doubles as an ABS sensor). As you found out (and pictured in your last pic), it is a hall-effect solid state device and interfaces to the tone ring that is pressed onto the rear axle's carrier. Being a solid state device, this VSS is not gear driven. This is the reason why an electronic device is required to offset the effects of larger tires on generation 2+ explorers.

Lono, just go to a transmission shop, or a higher end auto shop that will have the programmer for it. Some Brake shops (Midas) might even have that programmer. They also use it to bleed the ABS system in 98+ Explorers. That same device can reconfigure the speedo for you.

We did it on Turdles rig at 3am once. Just happened to have someone with us, that had the keys to the local Ford dealer, and "Borrowed" it because we got air in the ABS system(needed to bleed it). We changed out the axles with diff gears, and larger tires. So we used that same programmer to take care of the speedo at the same time.

91-97 have a gear driven mechanical VSS that uses different tooth gears, such as the one you bought. They are either in the T-case, or the trans tail shaft in 2wd.

The signal comes from the sensor on the output shaft, same sensor as the ABS on the diff. You have no use for the gear they sold you. As stated, it is a programmable parameter.

ncranchero said:

The signal comes from the sensor on the output shaft

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Is this also the case for 4wd vehicles? Because if its from the transmission's output shaft, then putting the vehicle in 4LO will throw off the speedometer by ~150%.

To clarify this, the Speedometer receives it's signal from the PCM. See diagrams below.

FOMOCO Service Manual:

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Fordparts.com:

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ncranchero said:

IIRC it's in the T-case on 4x4's.

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I dunno which t-cases this ST generation came with. But if it came with the 4405, wouldn't that make 1354 swaps difficult as the 1354 has a different VSS setup?