Ford Speedometer

[rzonk]

I have a 2004 Itasca on a ford v-10 chassis,I replaced the rear diff (changed ratio) and now my speedo is off almost 25% the info from ford says they use abs speed from rear diff,even if I change this info nothing changes,I think they are using the trans output speed sensor,does anyone know if I can change it or how to get the speedo accurate? I called Itasca and they told me to call ford, ford just says it should be from the abs sensor anyone have a schematic ??? Ron

[Perry White]

No schematic, but I think it is a reprogram on the ECM. Ford can do it.

[Luv2go]

rzonk,

You can also try Mike at 5 star tuning. He should be able to help you with this.

[tderonne]

25% what did you change the ratio to?

I'm in the same boat. It does use the ABS for a speed signal, but also uses output shaft speed. It's too "smart" to simply believe the ABS speed apparently. I need to reprogram my PCM, know how to do it, just haven't done it.

Mine's an '04 too, if you have a 4.88 like me, I should get off my butt and fix both of ours. (My speedo is about 13% low, 4.88/5.38 and some original error)

[rzonk]

I have access to the Frord Factory scanner and I am a Dodge master tech so I understand how this works/changing the tone wheel rpm for the abs made no difference.anyone know what need to be changed and how to do it? I went from 538 to 430 ???

[rzonk]

still trying to figure out the website,I changed from 538 to 430,I have a ford scanned and we changed the tone wheel revs per mile and it made no difference,is there a way to just use the abs or do I need to change configuration in pcm and how do I do it, (im a dodge master tech so I do understand it,just dont know what to do) ron rzonk@netscape.com California. thanks

[Fiesta48]

Wouldn't it be easier to drive at a 60 seconds per mile between mile markers on a Interstate and mark it on the speedometer? That is 60 mph. LOTS cheaper too.

[Perry White]

Wouldn't the tone wheel speed be the same. Don't it read the ring gear? Ring gear speed is the same , the pinion spins faster with lower gears. If it reads the pinion it wouldn't match the front wheel speed.

[Mekanic]

I recently reset my electronic speedo in my 94 F-700 when i swapped 5.29s for 3.70s AND I went to a much shorter tire. Even though yours is a 04 it might have a older type of speedo. have you popped it out of the dash to see if it has any(8, 10, or 12) dip swiches?
You might look at this thread to see if looks anything like whats in there.
Speedometer Calibration Codes - Ford Truck Enthusiasts Forums
I have a Factory service manual for a 94 large trucks. sometimes the codes in the book work right on the money.

[KC1BUD]

Quote:

Originally Posted by rzonk I have a 2004 Itasca on a ford v-10 chassis,I replaced the rear diff (changed ratio) and now my speedo is off almost 25% the info from ford says they use abs speed from rear diff,even if I change this info nothing changes,I think they are using the trans output speed sensor,does anyone know if I can change it or how to get the speedo accurate? I called Itasca and they told me to call ford, ford just says it should be from the abs sensor anyone have a schematic ??? Ron

Until you get it figured out, you can use GPS for speed readings. 20 years ago or so I couldn't figure out why everyone was passing me on a two lane marked 55. Set GPS to read speed, once I had the input from the satellite, most of the passing stopped.