55 Speedometer haywire

Daves55Sedan

Daves55Sedan

Well-known member
The speedometer needle bounces and the needle moves to 90 MPH while slowing down.
I thought that the speedo cable core was twisting inside the speedo cable housing, so that while slowing down, the core was un-winding faster to try to catch up.
I remove3d the old speedo cable. It was a factory original assembly. I pulled the core out and lubed it with grease and re-installed it.
No change.
I removed the cable again and installed a brand new repro cable assembly.
Still no change, it seems even worse now with the new cable.

I can turn the end of the speedometer under the dash with my fingers. So I dont think thats the problem.
Stumped.
 
If you replaced both the outer and inner parts of the cable, the problem is most likely in the speedometer itself. May need lubrication.
 
Your speedo is 57 years old. It works by spinning a magnet inside a metal drum. Both these spinning wheels run in bearings. If either one is dirty or dry your speedo will work erratically. If it really bothers you, you'll need to remove it and have a go at cleaning and lubricating the internals with a very light oil - something like the old sewing machine oil. The hair spring which dampens the needle moment may also need adjusting.
If you are not comfortable with playing around with it, take it to a good instrument fitter, speedo repair specialist or even a jeweler.
If you blow out the movement it would be better to use one of those aerosol cans which are clean dry air from Radio Shack or similar.
Just to make sure it is the speedo that is faulty, you can run the speedo using a cordless drill to check that it reads steady throughout its range. You may need to use a drill that is reversible depending on the rotation of the speedo.
Regards
 
there is a small plug on top of the speedo where the cable screws on, remove the welsh plug, under it you will find a felt plug, remove it and soak it in gasole or paint thinner to clean it, dry and put some sewing machine or 3n1 oil on it, put 4 or 5 drops of the oil in the hole where the plug was, turn the shaft with your finger till it turns free, replace the felt plug and another couple of drops to it replace the welsh plug, make sure no grease from the cable has worked its way into the speedo where the magnets turn inside the speedo needle housing, if it gets there it will grab the needle housing and drive the needle crazy when you drive
 
Theres nothing wrong with the original cable. I'm tempted to take out the repro cable and put the old one back in.
Looks like I'll need to tear out the instrument cluster after all. Hate to think about it. I know the way I am, I wont put it back unless everythings perfect. The paint on the metal part of the cluster dome is sunburnt and chipping off in some spots. The whole top of the dash is like that. This could turn into a huge project of tearing out the dash, stripping, repainting and might as well rewire the whole thing too while the dash is out. Been wanting to re-wire it for several years. This could be the excuse to do it finally.
 
frank long island said:
now is the time to enjoy it do that during the winter when its laid up
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It is NEVER "laid-up". I use it for work every day, and errands on weekends.

Nevertheless, I ripped out the instrument cluster and removed the speedo. It was completely inundated with grease. I removed the odometer from the speedo and dunked the speedo in a can of solvent. After soaking a while, it still had a lot of grease packed in the mechanism, so i got a can of spray gumout. That did the trick. The gumout blew out all the grease. Now I will let it dry for a day, then I will oil it with 3-in-1 oil.
Meantime, I also stripped the bad paint off the pot metal dome parts and refinished those, so at least they will look nice, although, it will put the rest of the dashboard to shame.
 
Had a chevy once with a loose speedo drive gear at transmission acted same way !
 
pat said:
Had a chevy once with a loose speedo drive gear at transmission acted same way !
Click to expand...

Well, thats a chebby for ya. That would be impossible on a Ford-O-Matic. The drive gear is locked onto the output shaft with a big spring clip. Its actually harder than hell to remove. The speedo driven gear cant bounce around either. The gear shaft fits into the cable housing more than an inch, and the gear end is held in place by a divet inside the extension housing. The tolerance is very close, probably less than 1/32 inch.
 
Since you guys seem to know...I replaced my speedo cable on my 55 Fairlane, but it won't fit snug into my ****** with the old plastic gear, no matter how hard I push on it. It needs about another 1/16 of an inch to be flush. It won't drive the speedometer at this point so I'm thinking of just buying another plastic gear. It didn't work when I got it anyway. How would I know how many teeth? Dennis Carpenter list 19, 20, 21, and 22. Nothing's simple....
 
If I ever had any trouble with getting the cable housing all the way into the transmission extension housing it was because I had installed a new rubber o-ring seal on the cable housing. But that would have been a fight to get about the last 3/16 inch to go in. If you are already past the o-ring, you may have the cable turned at the exact spot where the driven gear tooth is hitting the drive gear tooth.
If thats true, go up top and turn the cable at the top end just slightly then go back under the car and try it again.
If the cable housing is the original factory part, it should go back in without too much of a fight. It is a tight fit with the o-ring. Try turning the 7/16" hex bolt down on your clamp to see if you can get the last 1/16 inch to go down. There is enough flex in the inner cable that you should be able to get it down without a lot of force.
 
Also, you need to be careful not to allow letting the driven gear fall out of the cable housing once you get the cable started into the hole. I suggest coating the outside of the nylon gear with heavy bearing grease and then inserting the gear into the cable housing so the grease will hold it in while you are installing the cable into the trans.
But if you only got 1/16 inch to go, and your gear didn't fall out on the way in, that shouldn't be causing your problem.
 
I'll try the twist move. Yeah, I had to take the tailshaft off originally as the gear fell off when I removed the broken original cable. Anybody want to buy a 55 Fairlane? :(
 
You don't need to remove the tailshaft if the gear falls out of the cable housing. Stick one finger in the hole to feel where the end of the gear is. It is usually right behind the hole. Now cut a coathanger so that you have a peice about 5 inches long. Bend it it the middle to fashion it like a pair of tweezers. Then bend a little portion of both end of the tweezers down 90 degrees. Stick your tweezers in the hole and move them down till you hit bottom. Squeeze them together, pick up your gear and pull it out of the hole. Keep your special tweezers in a toolbox full of special tools you have so you don't loose them as you may need them again. But if you grease the end of the gear before sticking it in the trans, you shouldn't have a problem with it falling out.
No matter what type of project you are attempting, these are the easiest cars in the world to work on. With a little innovation and patience, a project can go relatively smoothly, even if something goes wrong during dismantling or re-assembly.
 
Read all through this thread with interest. My 55 F-100 has a similar problem. If I go a week or so with out driving it the speedometer needle will bounce back and forth for several miles until it works correctly. This past Spring I pulled out the inner cable and speared the white grease to it and dripped some oil on the felt. From what I have just read I guess I should pull out the cable and clean all the grease off and go with the described light oil instead? - John
 
When I was in auto shop in school, (just past the wooden wheel era), it was recomended we clean the cable, and grease only the bottom 2/3 to prevent grease from walking up the spirals on the cable into the speedo head. We were told to use a very light grease like Lubriplate Number 2.
 
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