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Discussion Starter #1
OK so driving down the road, 40mph, truck down shifted, looked down to a dead speedometer and odometer, now I have VERY hard shifts.

Speed sensor in rear end?
 

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Discussion Starter #4
Got back in it, after waiting on my daughter, and all was fine on the way home. Pulled it and not dirty, or any visible defects on it.

I have had an ABS light randomly over the past few weeks, but every time I would have the ABS light, truck would shift fine, and speedometer, and odometer would always work,

I guess I'll be stuck till the problem shows itself again :(
 

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OBS junkie
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Have you checked fuses under the dash yet? Mine would blow #8 (I believe) time to time & I would loose my speedometer. Check all fuses first.
 

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Discussion Starter #8
I'll double check the fuses, though I wouldn't imagine it to come back after going out? But I'll replace it just in case, there is an issue!
 

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Discussion Starter #9
Fuses, good, also noticed that the one marked for the speedo, is also tied to the radio, and that was working during this issue.
 

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Demon Dually
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5,140 Posts
You have a bad PSOM inside the instrument cluster. The only way to fix that is to replace the cluster. If it was the VSS it would only affect the speedometer and the ABS. The fact that the odometer goes out as well narrows it down to the PSOM.
 

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Demon Dually
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I won't argue about it but it is a well known fact. It happens to the vans and trucks from this era, gas or diesel.
 

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And a bad rear differential speed sensor would affect the Speedo, Odometer, and ABS. NEVER jump to a conclusion that one thing or another is the only cause of a particular symptom. The minute you do, you will find a situation that makes you realize that. Trust me on this one. every answer that was given COULD be a possibility.....and all of them COULD be wrong.

If i had to give my stab at this with the limited info given, i would say rear diff speed sensor.

Do you have a way to get the ABS code that was thrown? That would be a big help.
 

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If it was the VSS it would only affect the speedometer and the ABS. The fact that the odometer goes out as well narrows it down to the PSOM.
this is untrue. If the cluster cant calculate speed, then how can it calculate miles driven (miles driven is calculated on SPEED and tire revolutions)
 

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Demon Dually
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It is my understanding that the OP's odometer is shutting off completely. Explain to me how the VSS would turn off the odometer. It can't. It does not power the odometer in any way.
 

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It is my understanding that the OP's odometer is shutting off completely. Explain to me how the VSS would turn off the odometer. It can't. It does not power the odometer in any way.
a vehicle with 4 wheel abs can turn the odometer completely off when the rear diff VSS doesnt match the front two. In a vehicle with rear abs the odometer will just stay the same. It depends on what you are dealing with....and on the internet i have learned to NEVER assume.
 

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Demon Dually
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No obs ever came with 4 wheel abs. They were only equipped with RABS. Rear Anti-locking Braking System. Which actually is not ABS at all. It simply dumps the pressure to the rear brakes in a panic braking situation. A real ABS system would "pump" the brakes in order to slow the vehicle without "locking" the brakes in a panic stop. While I understand that assuming is a bad thing to do, I didn't assume anything. I took all of the data that was provided and answered his question correctly. If this had been a SD which could have 4 wheel ABS then I would have said yes it could be the VSS but without the odometer being lit up at all there is only a few options and none of them point to a VSS. Of course on a SD you would also have to take into account that it could be the OSS as well being as they are equipped with a 4r100 which has the OSS where as the e4od does not. Another option if the odometer was lit be it an OBS or SD count be the tone ring on the rear or on a SD it could be a tone ring on the hub assembly, or like I have seen a Ford mechanic do at the dealership is to run the wiring from a new sensor in between the rotor and backing plate which cut the wiring in a matter of seconds of driving it. Just saying.
 

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we had a lot of trouble with this on a super duty once.... changed not only the sensor in the diff but also the harness. took it in to a mechanic he couldn't get it took it to the dealership and they said they checked every connection to the abs module and still couldn't get it to communicate with their tester. They said the module was shot and they would replace it for just under 1000. Told them to piss off and went to get the codes off the module so we could find one at a salvage yard and just happened to find the ground was loose. It had a ground from the computer grounded to the radiator support, tightened it up and haven't had any issue since. Something worth checking before replacing anything or throwing money at it.
 

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Discussion Starter #19
Correct, when this issue happens, the odo goes DEAD completely, it doesn't just top clicking off miles, it goes blank as if the key was shut off.

I have searched over and over for loose grounds and wiring issues, to no avail.

On the good side, it didn't do it any today, I'd rather have an issue 100% of the time so I could trouble shoot, than an intermittent one any day!
 
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