1993 f250 7.3 IDI speedometer all over the place!!

[InnovativeAV]

So I was up on the highway today doing about 60 mph. And my speedometer started bouncing all over.


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[ToughOldFord]

Clean/replace the VSS. Located top of the rear differential.

 

[InnovativeAV]

Thats what I figured but wanted to ask first....the transmission shop that just did the transmission was telling me it was the Tefal behind the cluster. Ford told me this truck never had that

 

[FoolhardyIDI]

Another place to check is the speedo gear in the trans. When I bought my truck the speedometer was fluttering quite a bit. I was told to replace the VSS on top of the rear diff. I did and still had the problem. Took out the speedo gear in the trans and the teeth were chewed up on the plastic gear.

 

[FORDF250HDXLT]

if you have an E40D try not to drive it at all like that.it could do serious damage.if it's not the VSS (it will be located at the top of the rear axle in '93) then suspect the PSOM itself.if you want to try fixing it yourself here is how;
http://www.harleyhummerclub.org/PSOM/index.html

im pretty sure there is a place that fixes them too.iv seen an video ad for them on youtube.

 

[FORDF250HDXLT]

found it;
http://lmgtfy.com/?q=Ford+PSOM+speedometer+repair+service+for+F+series+trucks+&+Bronco

&

more how to;
https://www.youtube.com/watch?v=WsN5owpxCXQ

^ ok so he's not rebuilding it there.he's changing it out for another.still helpful info on how to pull it all apart (but it's all pretty straight forward anyway) the thing about doing this is your odo will be wrong.no problem really,just write down your odo's true mileage first so you always know whats on your truck.

 

[ToughOldFord]

Another place to check is the speedo gear in the trans. When I bought my truck the speedometer was fluttering quite a bit. I was told to replace the VSS on top of the rear diff. I did and still had the problem. Took out the speedo gear in the trans and the teeth were chewed up on the plastic gear.

Just so you know, your truck being a '91, was the last year to have both. The speedometer gear at the transmission works the speedometer, the VSS is for the anti-lock brakes.
Starting in '92 the VSS served both function; so no gear at the transmission in the OP's truck.

 

[FoolhardyIDI]

Wow so it went to an electronic speedometer then. No more speedo cable.

 

[ToughOldFord]

Yep.

 

[BigBlueOBS]

Could be the speedo gear in the rear axle, I have that problem but I just removed the gear since im running 46's and its 20mph off and I use my phone gps speedo


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[BigBlueOBS]

BTW the ring gear teeth will take out that gear... Sorry to make u wonder now but that's what happened to me


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[79jasper]

Could be the speedo gear in the rear axle, I have that problem but I just removed the gear since im running 46's and its 20mph off and I use my phone gps speedo
BTW the ring gear teeth will take out that gear... Sorry to make u wonder now but that's what happened to me

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What gear?
The sensor at the rear end is electromagnetic.
Far as programming for bigger tires, it's pretty easy diy process.

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[BigBlueOBS]

What does the electromagnetic sensor run off of? A gear.


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[FORDF250HDXLT]

What does the electromagnetic sensor run off of? A gear.


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it doesn't "run" off anything.your thinking mechanically when you need to think electrically.it's magnetic pulses.there is a tone ring in there but it's not to drive a gear but rather to provide a gap to toss the no magnetic to a magnetic pulse as it spins see? then the sensor reading this pulse between the "blank spots" sends the electrical info to the psom where does it's conversion and makes the needle read the trucks speed (and for E40D trans equipped trucks,it sends the info to the control unit as this info is vital and required for it to know which gears to select.) nothing for gears.

 

[BigBlueOBS]

Ya the tone ring! I couldn't think of the name but it looks like a gear but just has the sensor above it!


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