Speedometer Question from newbie

Fibber Mcgee

Fibber Mcgee

Well-known member
I just joined,been reading posts for a while though.I have a 49 f1 with 3speed and original speedometer but when I hook up cable speedometer shows twice actual speed.I have had two different trans in truck with same problem anyone ever seen this.Great website,already learned alot!
 
to me it sounds like the speedo gear in the trans is to small, if you go up 2 teeth on that gear it will slow down the speedo by about 10 to 12 mph
 
HEY FIBBER: I've been sitting here looking at your question, and how can I answer / explain it ?? In side your speedo,the cable drives a disc, or cupped disc. sitting inside the cup is magnet connected to the needle ( the cup and the magnet are not connected ) the magnet is CLOSE to the cup. So the faster the cup spins, the magnet moves the needle to show the speed on the dial, To calibrate your speedo the cup or the magnet is moved in or out. ...
To put it simply "" YOU HAVE SOME JUNK IN YOUR CUP "".... now what to do ??
Get the instrument out of the case. and clean it out, don't blow HARD air in there, wash it with WD40 a good bath some light air or a vacuum, now some GOOD oil, like some from a gun shop, spray in and dry it out. ...The clearance between the cup and the magnet is close, so dirt, dust, spider web, what ever, or a hard hit, will make it do what you have. ... you can do it just clean it out... and you good to go. .... OLD...BILL
 
Thanks OLD...BILL I'll try that,I hope that is it.I will pull the speedometer this week and see what I've got. Thats what I like about this website,one day and I already got two ideas I had not thought of yet.
 
not that Bills idea in not a good one, but if the magnets touch the inside of the cup any where it will jerk the needle all the way over to the side and hold it there, the magnets must run free , not touching anything to work right
 
Ok I'm going to pull it and see,I'm just glad to hear it could be something simple.One more thing it bounces real bad at anything under 45 and then gets better the faster you go.
 
when you getthe speedo assembly out of the housing you will find a small welch plug right near where the speedo cable screws on, remove the plug and the felt wick under it, put in some sewing machine or 3 n 1 oil turn turn the soeedo shaft till it turns free with your fingers, wet the wick with oil, replace it and add a few more drops of oil on top of it, repace the welch plug, carefully oil all the speedo gears you can get to, dont over oil any of them, its the speedo needle shaft that gets dry for lack of oil because it is so much trouble to get to, when dry it will cause the speedo needle to bounce
 
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