intermittent speedometer
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Junior User
Joined: Jun 2003
Posts: 90
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From: Newton, Kansas (3 syllabl
intermittent speedometer
Just bought an 81 f250, light duty, 4wd, 300/t18. The speedometer/odometer is unreliable - they can just stop working. They'll start out fine, but after several miles the speedo will beging a gradual and uneven float down to zero. By that point, the odo will have quit as well. The faster I go (say, 65-70), the more likely the speedo will continue to function. Anyone have a clue on this?
Post Fiend
Joined: Mar 2003
Posts: 14,413
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From: Sarnia, Ontario, CANADA!
We had the EXACT same problem with a 79 F350 at work until it got to the point where it doesn't work at all. I would "guess" a stripped gear in the tranny, speedometer cable broken, or speedo cable came out of the back of instrument cluster. Those are my guesses. Haven't figured out the problem yet but will "someday"! 
-Matt
-Matt
Posting Guru
Joined: May 2004
Posts: 2,223
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From: Billings Montana
It could be one of two things, it's either the cable or the speedometer itself.
If it is the cable, it's not an easy thing to do, sorry. You have to take the instrument cluster apart and pull the cable off the back. Then fish the cable thru the firewall and disconnect it at the tranny.
If it's not the cable itself, then it's the speedo and you still have to take the panel apart. Trust me, it sucks 'cause I had to do this a few weeks ago. I replaced the speedo with one in the junkyard and it's squealing again!
If it is the cable, it's not an easy thing to do, sorry. You have to take the instrument cluster apart and pull the cable off the back. Then fish the cable thru the firewall and disconnect it at the tranny.
If it's not the cable itself, then it's the speedo and you still have to take the panel apart. Trust me, it sucks 'cause I had to do this a few weeks ago. I replaced the speedo with one in the junkyard and it's squealing again!
Senior User
Joined: Dec 2003
Posts: 118
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Hi
Unbolt the speedo cable from the tranny (3/8 bolt) take the speedo gear off the spindle (there is a metal clip holding it on), put a drill on it, turn it on and then have a look at the speedo and see if it is doing the same thing, get some-one underneath to vary drill speed while you watch speedo. Check out the condition of the speedo gear for wear, should be nice and symetrical, also put your finger in the hole where the speedo cable came out of. You will feel another drive gear (this is the output shaft drive gear) check for wear. Hopefully it is the speedo gear on the end of the cable, if you have to replace the output shaft drive gear it is a pain in the a***. If it is the speedo cable you have to replace, they are simple to put in.
Chris
Unbolt the speedo cable from the tranny (3/8 bolt) take the speedo gear off the spindle (there is a metal clip holding it on), put a drill on it, turn it on and then have a look at the speedo and see if it is doing the same thing, get some-one underneath to vary drill speed while you watch speedo. Check out the condition of the speedo gear for wear, should be nice and symetrical, also put your finger in the hole where the speedo cable came out of. You will feel another drive gear (this is the output shaft drive gear) check for wear. Hopefully it is the speedo gear on the end of the cable, if you have to replace the output shaft drive gear it is a pain in the a***. If it is the speedo cable you have to replace, they are simple to put in.
Chris
