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Discussion Starter #1
Got a 1999 Ford F-250 7.3 truck was driving great until Speedo stopped working and od started flashing then I blew my trans so I got it rebuilt 3000 later and the Speedo isn’t working and od still flashing and it’s shifting funny my buddy said it needs a Speed sensor so we replaced it I’m still getting the same code and Speedo still ain’t working and od is still flashing trucks shifting funny won’t down shift on highway any ideas checked all my fuzes replaced speed sensor twice checked wiring only thing I can think of is the cluster being bad any ideas
 

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Your truck has been hanging around the strip clubs too much lately. (Usually, a bad VSS causes erratic operation.) ;)

You should get it scanned with a Powerstroke capable scan tool. That will let you know where to look. How did you check the wiring? A continuity test between the VSS and the instrument cluster is the best thing to do to find wiring issues. They aren't necessarily detectable by a visual inspection.

Welcome to TheDieselStop :)
 

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Well, I really like my truck but I dont get quite that excited about our seat time together 😉. If you are referring to the speed sensor on top of the rear differential perhaps its not the sensor but the sensors target on the ring gear assembly and or the media, gear oil, is contaminated with metal shavings fouling the signal count per revolution.
 

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Make sure that the new VSS is seated fully down on the housing. I had that problem.

I'm guessing here but does the Super Duty wires to directly to the cluster or do they terminate at the PSOM?

Also how did you check the wiring? Did you do a end to end continuity test?
 

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Vss erotic shifting
Well, this thread should get a lot of attention 😉, no worries a little humor is needed around here every now and then.

Welcome to the forum
 

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Discussion Starter #6
Well, I really like my truck but I dont get quite that excited about our seat time together 😉. If you are referring to the speed sensor on top of the rear differential perhaps its not the sensor but the sensors target on the ring gear assembly and or the media, gear oil, is contaminated with metal shavings fouling the signal count per revolution.
Hahaha thanks so u think I should take rear diff cover off and see what’s inside
 

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Not necessarily, pull the sensor out and look down in the opening with a mechanics mirror first. If I saw any obstruction or shavings on the sensor, target cogs or in the opening then I would open the differential, or if its time to service it now is the time. But at any rate I would make certain the opening and target cogs are metal debris free.
 

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You can also get a magnetic fill plug to see if you have metal in the lube.

My first VSS went out around 6 months after I had changed the fluid in the diff and installed the magnetic plug. I checked the plug and didn't have any metal sticking to it. I also didn't pull the cover but vacuumed out the fluid

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What does the shop say?
That $3,000 oughta buy you some advice and concern they will soon have a warranty repair.
 
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