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Discussion Starter #1 (Edited)
All of a sudden yesterday I noticed my speedo showing 95mph when my GPS speed was appox 60. Shut engine down when I arrived home and it read 37MPH. This morning still showing appox 34MPH cold with ignition off. Start up and drive speedometer still appox 37MPH high.

Any ideas where to start looking ?

TIA

Harry
 

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I see you're not getting any response to your issue. I once had a speedometer issue too, but my issue was that the speedometer wouldn't move until I was doing about 30 mph, and as long as I stayed at 30 or above, it worked fine. I ended up replacing the sensor on the rear differential, and it fixed my problem. I can't guess as to wheather it would fix your problem, but I don't recall the sensor being very expensive. Best of luck.
 

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Discussion Starter #4
I see you're not getting any response to your issue. I once had a speedometer issue too, but my issue was that the speedometer wouldn't move until I was doing about 30 mph, and as long as I stayed at 30 or above, it worked fine. I ended up replacing the sensor on the rear differential, and it fixed my problem. I can't guess as to wheather it would fix your problem, but I don't recall the sensor being very expensive. Best of luck.
There were a few model years we saw this problem. Replace or have the cluster repaired. Your favorite Ford dealer can assist you with that or try one of these:
  1. https://circuitboardmedics.com
  2. https://www.instrumentclusters.com
  3. Automotive Electronics | United Radio
My dealership uses United Radio for all of our radios and clusters.

Thanks guys. Recently the RPM's are also reading approximately half. I punched in MPH in my Scangauge and the readout is accurate to my GPS speed so most likely what Ford Doctor said my cluster needs repair.
 

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Discussion Starter #5
Just an update: Never was able to resolve the speedometer issue as it was an intermittent one. Last week had the transmission stuck in Tow Haul. Had the truck flatbedded to and repaired at a Ford dealership (if you find yourself locked in Tow Haul don't drive it too far). Turned out to be the Lead Frame in the transmission. Since the repair the truck speedometer has been functioning fine.

From what I understand from the information I've been able to garner on the internet about the lead frame (mostly youtube), there is a sliding part on the lead frame that is associated with the speedometer. So this issue with my speedometer MAY (emphasis on "may") have been associated with the eventual problem that developed with the transmission. I could be wrong. Just wanted to post this info which may be of use to someone in the future.
 

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Just an update: Never was able to resolve the speedometer issue as it was an intermittent one. Last week had the transmission stuck in Tow Haul. Had the truck flatbedded to and repaired at a Ford dealership (if you find yourself locked in Tow Haul don't drive it too far). Turned out to be the Lead Frame in the transmission. Since the repair the truck speedometer has been functioning fine.

An open or short in that harness will in most cases result in a flashing Tow Haul lamp and the transmission will be operating in 5th gear only by default. Additionally your Check Engine and Wrench lights may also illuminate. I am thinking that this is more than likely what you experienced as a problem with the Output Shaft Speed sensor or related wiring would indeed cause this. I am guessing it was that sensor that was affected since you seem convinced this incident is related to your speedometer concern.


From what I understand from the information I've been able to garner on the internet about the lead frame (mostly youtube), there is a sliding part on the lead frame that is associated with the speedometer. So this issue with my speedometer MAY (emphasis on "may") have been associated with the eventual problem that developed with the transmission. I could be wrong. Just wanted to post this info which may be of use to someone in the future.

Electrically, there are no parts or sensors in your Torqshift transmission that are used for vehicle speed information in 2005 model year Ford trucks. VSS data is provided by the ABS module which is hardwired to the instrument cluster on your 2005 Super Duty, otherwise the VSS data is provided to all modules requiring it by a network. In this case the single ABS sensor in the rear axle provides speed indication. The Speed sensors in your transmission (Turbine Shaft, Intermediate Shaft and Output Shaft speed sensors) are used solely for determining transmission operation and fault detection, not vehicle speed.

So, yes, your cluster concern was likely not corrected by your internal transmission harness issue.

One more tid-bit of info for ya - when the cluster does not receive VSS data it will read zero. If the speedometer is that inaccurate and intermittently reads on the 30's with the key on, engine off and the vehicle not moving, your cluster is bad. Sorry to sound repetitive.
 
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