speedo oddity
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Tuned
Joined: Jun 2008
Posts: 266
Likes: 7
speedo oddity
I've had this problem since I bought the truck 4.5 years ago, kindof annoying but not a priority to fix.
When it's below 50 degrees outside and I take off the speedo doesn't go up until I get to about 25, then it races all the way up to 70. If I slow down it will go back down to 0 until I've accelerated for a few seconds. It takes a few miles of driving before it settles into the proper spot and then registers correctly until it has been parked for 20-30 min.
The odometer isn't affected by this, I've checked it several times and it registers correctly through the whole process.
What I've tried, to the best of my memory as it's been a while... Bought a new speed sensor and installed it in one of the 2 spots, don't remember now which one someone recommended. That didn't work so a few months later I swapped the two sensors. I've changed the oil in the rear diff and visually checked the tone ring and everything inside there.
Any ideas?
When it's below 50 degrees outside and I take off the speedo doesn't go up until I get to about 25, then it races all the way up to 70. If I slow down it will go back down to 0 until I've accelerated for a few seconds. It takes a few miles of driving before it settles into the proper spot and then registers correctly until it has been parked for 20-30 min.
The odometer isn't affected by this, I've checked it several times and it registers correctly through the whole process.
What I've tried, to the best of my memory as it's been a while... Bought a new speed sensor and installed it in one of the 2 spots, don't remember now which one someone recommended. That didn't work so a few months later I swapped the two sensors. I've changed the oil in the rear diff and visually checked the tone ring and everything inside there.
Any ideas?
Hotshot
Joined: Jan 2011
Posts: 18,849
Likes: 179
From: Puget Sound
That sounds like a dash problem to me. The shifting wouldn't work right and the ABS system would freak out with alarms if you truly lost a speed sensor. I'll bet a number of your dash bulbs are burned out after all these years anyway. So... this would be a good time to pull the dash, replace the bulbs, clean the hardware and electrical connectors, and put some Deoxit on the connectors.
New User
Joined: Jan 2017
Posts: 2
Likes: 0
I am having the about the same issue with my 1991 f350 except all my dash lights work and nothing is burned out i pulled the dash apart and all the wires are intact and together neatly i already replaced the transmission speed control sensor but am having the same probles as before any other ideas
Hotshot
Joined: Jan 2011
Posts: 18,849
Likes: 179
From: Puget Sound
Good connections and sensors with the bad speedo? That could be all there is to it - a bad speedo. If it were my rig, I'd put an O-scope on the signal in, but I'm unsure what to suggest for those without a background in electronics. Maybe somebody else has an idea beyond a swap-out - but don't get your hopes up.
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