Speedometer 6MPH high
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8th Gear
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Speedometer 6MPH high
Just got a 2012 F-150 XL 4x4 w/101K miles. It was a fleet truck in North Dakota. Speedometer is reading about 6 MPH high everywhere from 25MPH up to 70MPH (and beyond I assume). Took to dealer and they reset computer to current tires (265/70R17), but that made no difference (not surprising) since the calculation shows they are only 0.5% different (speedwise) from stock LT245/75R17 tires.
I did notice something on the Carfax - at 12K miles the axles were checked and differential ring gear & pinion replaced. I assume that wouldn't have an impact, but it seemed weird. Is there anything else axle/differential related that I should look for?
I've seen the threads on calibrating the speedometer myself, but not I'm comfortable with that. I'm taking it back to the dealer - is there anything specific they should do?
Thanks,
Mark
I did notice something on the Carfax - at 12K miles the axles were checked and differential ring gear & pinion replaced. I assume that wouldn't have an impact, but it seemed weird. Is there anything else axle/differential related that I should look for?
I've seen the threads on calibrating the speedometer myself, but not I'm comfortable with that. I'm taking it back to the dealer - is there anything specific they should do?
Thanks,
Mark
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Speedo can not be off 6 MPH at 25 and also at 75 MPH....... it is linear... If it was off 6 MPH at 75, it should be off 2 MPH at 25... Your talking about 10% off in speed.. That would be hard to do.. Where are you getting the 6 MPH ?
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8th Gear
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I understand what you are saying - I would have expected it to be linear also. But I checked it against my GPS (which is confirmed accurate in other vehicles) and against mile markers. Speedo was was probably reading 5 low at 20 MPH, then 6 low at 60 MPH, so there's a very slight change but definitely not linear. It seems like there just a constant offset of 6 MPH.
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8th Gear
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Unfortunately I have an XL with just the analog gauge and minimal digital information.
But based on previous comments I just checked the speedometer when stationary and it shows well below zero. By the time it gets up to zero the GPS shows 8MPH, so it does appear to just be a constant offset.
I plan to just pull off the instrument gauge cover and zero out the needle. Will that have any unintended consequences, or anything I should be careful about? Thanks!
But based on previous comments I just checked the speedometer when stationary and it shows well below zero. By the time it gets up to zero the GPS shows 8MPH, so it does appear to just be a constant offset.
I plan to just pull off the instrument gauge cover and zero out the needle. Will that have any unintended consequences, or anything I should be careful about? Thanks!
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Hotshot
Joined: Jul 2005
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you might look up on You Tube or something like that... Setting it at ZERO might be one idea... I did an explorer several years ago and it seems like you connect a 1.5 volt battery to a couple terminals, then put the needle on at 60 MPH or something like that...
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From: Brentwood,CA
Unfortunately I have an XL with just the analog gauge and minimal digital information.
But based on previous comments I just checked the speedometer when stationary and it shows well below zero. By the time it gets up to zero the GPS shows 8MPH, so it does appear to just be a constant offset.
I plan to just pull off the instrument gauge cover and zero out the needle. Will that have any unintended consequences, or anything I should be careful about? Thanks!
But based on previous comments I just checked the speedometer when stationary and it shows well below zero. By the time it gets up to zero the GPS shows 8MPH, so it does appear to just be a constant offset.
I plan to just pull off the instrument gauge cover and zero out the needle. Will that have any unintended consequences, or anything I should be careful about? Thanks!
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I agree that changing a gear ratio during the Carfax event would have given a wider difference as speed accumulated. I also agree tire-size difference between stock and current is only 0.3% by my math, which would yield a 1MPH difference at just under 334MPH.
The +6MPH thing makes sense to me as a spindle-clocking problem with the speedometer stepper motor until I read posts 3 and 7. Then I get:
indicated=actual (source) offset=(actual minus indicated)
-1=00 (from post 7) offset=-1
00=08 (from post 7) offset=08
15=20 (from post 3) offset=05
19=25 (from post 1) offset=06
24=30 (from post 1) offset=06
29=35 (from post 1) offset=06
34=40 (from post 1) offset=06
39=45 (from post 1) offset=06
44=50 (from post 1) offset=06
49=55 (from post 1) offset=06
54=60 (from post 1) offset=06
59=65 (from post 1) offset=06
64=70 (from post 1) offset=06
So it appears to be non-constant after all? If true, this would strike me as more than a spindle clocking issue with the needle on the stepper.
If it were me, I'd use TorqueOBD2 or similar to observe the speed that the computer thinks it is doing versus the indicated speed on the speedometer. If that showed the same as has been posted in this thread, I'd grab a cluster from a junkyard and see what it does across the same range.
The +6MPH thing makes sense to me as a spindle-clocking problem with the speedometer stepper motor until I read posts 3 and 7. Then I get:
indicated=actual (source) offset=(actual minus indicated)
-1=00 (from post 7) offset=-1
00=08 (from post 7) offset=08
15=20 (from post 3) offset=05
19=25 (from post 1) offset=06
24=30 (from post 1) offset=06
29=35 (from post 1) offset=06
34=40 (from post 1) offset=06
39=45 (from post 1) offset=06
44=50 (from post 1) offset=06
49=55 (from post 1) offset=06
54=60 (from post 1) offset=06
59=65 (from post 1) offset=06
64=70 (from post 1) offset=06
So it appears to be non-constant after all? If true, this would strike me as more than a spindle clocking issue with the needle on the stepper.
If it were me, I'd use TorqueOBD2 or similar to observe the speed that the computer thinks it is doing versus the indicated speed on the speedometer. If that showed the same as has been posted in this thread, I'd grab a cluster from a junkyard and see what it does across the same range.
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8th Gear
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Thanks to all for the helpful advice. I've got a Forscan adapter coming Wednesday (and now a Bluetooth adapter as well), so I'll see what speed the computer is showing. I did a rough check with my automatic locks today - they locked as expected at 12MPH on the GPS.
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8th Gear
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