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1987 - 1996 F150 & Larger F-Series Trucks 1987 - 1996 Ford F-150, F-250, F-350 and larger pickups - including the 1997 heavy-duty F250/F350+ trucks

speedometer bouncing

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Old Nov 3, 2025 | 08:15 AM
  #1  
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From: rust belt
speedometer bouncing

its fairly accurate (slightly bouncing) up to about 30-35 then after that it just starts going haywire. I bought a new vss (the one on the diff) Saturday and replaced it. I went from no speedometer and odometer not going up to a bouncy speedometer and a odometer reading. any help would be appreciated.


1994 Ford F150 XLT w/ 5.0 & E4OD 2wd
 
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Old Nov 3, 2025 | 02:42 PM
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From: Bahstun
Check VSS wiring to the dash and ohm it out too.
Change gear oil in diff? metal bits can fool it.
PSOM can go making you think its VSS related
 
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Old Nov 3, 2025 | 04:22 PM
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From: rust belt
Originally Posted by knottyrope
Check VSS wiring to the dash and ohm it out too.
Change gear oil in diff? metal bits can fool it.
PSOM can go making you think its VSS related
I ohmd the sensor before it went in and I was getting 1800-2000 ohms (apparently what is supposed to be around) but I also read that if it’s “too close or too far” from the tone ring it could cause issues yet the old one was in all the way? Not much of a electrical person so I’d have no clue how that’d affect it but when I get a chance I’m probably going to see what I can do about inspecting the tone ring from the vss hole (since that seems to be a common issue) and probably have a shop change it plus the oil if it’s a issue since I have no experience with differentials
 
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Old Nov 4, 2025 | 10:15 PM
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I heard somewhere and in another time that there is a capacitor on the PSOM that can leak and play havoc with the speedometer. Swapping the PSOM might be the easiest way get a look at that capacitor and to see if that's the problem.
 
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