1955 Speedometer erratic moment

[Selfrich]

What is the problem with my speedometer? It will move back and forth when driving around 30 to 50 MPH and then is steady on a speed when it is going 60-70 MPH. There is no noise coming from it (as I would expect if needed grease) just this steady movement at lower speeds?

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[zeroroadkill]

What is the problem with my speedometer? It will move back and forth when driving around 30 to 50 MPH and then is steady on a speed when it is going 60-70 MPH. There is no noise coming from it (as I would expect if needed grease) just this steady movement at lower speeds?

Difficult to get to, but there is a oil hole on top of the speedo housing where the cable connects. What I did, after removing and lubricating the cable which didn't help, was to take a hypodermic needle, bend the needle to a 45° and fill the syringe with 3in1 oil and soak the felt oiler pad. You'll need a flashlight, mirror and the ability to become a pretzel! The only other way I can think of is to remove the speedo to get to the oil hole. I had to oil it two times because it was hardened and dry.

 

[4VE]

The speedometer is a long, round, woven, spring-like, flexible wire with each end forged to a square. It is encased in a flexible contuit with screw on fittings at each end. One end of the core (wire-spring) goes into the spedo the other into the transmission tail stock. It probably is rusted inside and caused the spring to kink. Remove the conduit and pull the core. Use a gun cleaning kit with a brush end to remove any rust scale. Rinse it with lacquer thinner and a gun barrel cloth wiper. You can also do this with a looped piece of fishing line and draw the brush and swab through the conduit. Replace the core spring after thoroughly greasing it down with lithium grease then replace the whole thing. Make sure there are no kinks in the new one and be careful not to cause them when installing it.

 

[Ward 57]

Sounds like I will keep it erratic. ??

It isn't complicated. Just unscrew the cable from the speedometer and pull out the driving cable and check it's condition as you do. If it's just dry there is specific cable lube made of graphite grease and apply it liberally as you re- insert it. Any auto parts store should have it. Use it on your Tach cable too. You may have to twist it a bit to get it to seat into the driven gear in the trans.

 

[zeroroadkill]

Sounds like I will keep it erratic. ??

I tried removing the cable and cleaning/lubing it but my problem was the dry felt oil pad located at the top of the Speedo cable connector. Several drops of oil, and now it’s smooth as silk! Good luck.

 

[doug7740]

What is the problem with my speedometer? It will move back and forth when driving around 30 to 50 MPH and then is steady on a speed when it is going 60-70 MPH. There is no noise coming from it (as I would expect if needed grease) just this steady movement at lower speeds?

The speedometer has two main parts, the speedometer head and the speedometer drive cable. When the speedometer fails to indicate speed or mileage, the cable may be broken. Most cables break due to a lack of lubrication or a bend or kink in the housing. The cable also might break when the speedometer head mechanism binds. A jumpy pointer, along with a scraping noise, is often caused by a dry or kinked speedometer cable. The kinked cable rubs on the housing and winds up slowing down the pointer. The cable then unwinds, and the pointer jumps.

To lubricate the cable and check for kinks, the cable will have to be removed from the housing. It is not necessary to remove the housing from the vehicle. From under the dash, disconnect the housing by its fluted nut from the back side of the speedometer head. Prior to removing the cable from the housing, cover the carpet and upholstery, as the common lubricant is graphite which will really make a mess to whatever it touches. Using long nose pliers, pull on the cable while supporting the housing. The cable should come out fairly easily, unless there is a crimp somewhere in the housing, which could be the cause of the problem by itself.

With the cable fully withdrawn and out of the car, inspect the outer surface of the core for flat and shiny areas. These indicate wear areas and you can use their position to approximate the area of the housing that may have an excessive bend or kink. To check for kinks, lay the cable on a flat surface and twist one end with your fingers. If it turns over smoothly, the cable is not kinked. But, if part of the cable flops over as it’s twisted, the cable is kinked and should be replaced.

Before reinstalling the cable back into the housing wipe it down with a clean absorbent cloth and re-lubricate it with a graphite bearing lubricant. Then feed and twist the cable back into the housing. The last 3/8” to 1/4” will require twisting and pushing to engage the square drive at the far end of the cable.

Before re-connecting the cable housing to the back of the speedometer head, put a few drops of lubricant on the wick through the hole in the speedometer head. I had a hard time doing this so I removed the speedometer head from the dash. The speedometer can be removed from the back of the head on a 1957 model, so you do not have to remove the entire head.

doug7740
1955 Thunderbird Blue

 

[Frankie the Fink]

The speedometer is a long, round, woven, spring-like, flexible wire with each end forged to a square. It is encased in a flexible contuit with screw on fittings at each end. One end of the core (wire-spring) goes into the spedo the other into the transmission tail stock. It probably is rusted inside and caused the spring to kink. Remove the conduit and pull the core. Use a gun cleaning kit with a brush end to remove any rust scale. Rinse it with lacquer thinner and a gun barrel cloth wiper. You can also do this with a looped piece of fishing line and draw the brush and swab through the conduit. Replace the core spring after thoroughly greasing it down with lithium grease then replace the whole thing. Make sure there are no kinks in the new one and be careful not to cause them when installing it.

This ! And use Kable-Ease graphite lubricant is my only remark......lithium can harden and congeal over the years into a clay like bunch of clumps, I can't tell you how many classic car door hinges and latches I've had to blast that stuff out of after deacdes of sitting around.

 

[CuriousCarl]

My speedometer starter making a strange howling noise recently and the needle wouldn’t read right. I took it to a shop and they said that the bushing is probably worn through which causes the cable not to catch it. The guy reached under the dash and unscrewed the cable as a temporary fix (which obviously means I have no measurement of speed). He said (and I’ve read) that it’s a fairly common problem.

Is there a way to fix this without rebuilding the speedometer? I saw someone say that it might just need lubrication and to give it a drop or two of oil. Is this difficult to do? And if it’s not, what kind of oil should I use?

Thank you so much!

 

[zeroroadkill]

I posted a way to oil the felt at the top of the speedo housing where the cable screws in without having to remove the whole unit. Techniques may very but I used a syringe filled with light oil and bent the needle so I could get it in the weep hole. After that no more noise or jumping around. You can also pull the cable out clean and grease and reinstall as well. My guess if it was working smooth before it’s the dry felt in the speedometer head.

 

[Ward 57]

My speedometer starter making a strange howling noise recently and the needle wouldn’t read right. I took it to a shop and they said that the bushing is probably worn through which causes the cable not to catch it. The guy reached under the dash and unscrewed the cable as a temporary fix (which obviously means I have no measurement of speed). He said (and I’ve read) that it’s a fairly common problem.

Is there a way to fix this without rebuilding the speedometer? I saw someone say that it might just need lubrication and to give it a drop or two of oil. Is this difficult to do? And if it’s not, what kind of oil should I use?

Thank you so much!

First lube the cable with graphite speedo lube. Unscrew the cable from the speedo and pull the cable out and lube it liberally. Re-installation is not tough, just twist and spin until it seats into the driven gear in the trans.. There is also an oil port on the top that is hard to get to. With a mirror, you can find the port on the top of the input housing and give it some oil. Lube the tach cable while you are at it.

 

[doug7740]

My speedometer starter making a strange howling noise recently and the needle wouldn’t read right. I took it to a shop and they said that the bushing is probably worn through which causes the cable not to catch it. The guy reached under the dash and unscrewed the cable as a temporary fix (which obviously means I have no measurement of speed). He said (and I’ve read) that it’s a fairly common problem.

Is there a way to fix this without rebuilding the speedometer? I saw someone say that it might just need lubrication and to give it a drop or two of oil. Is this difficult to do? And if it’s not, what kind of oil should I use?

Thank you so much!

The speedometer has two main parts, the speedometer head and the speedometer drive cable. When the speedometer fails to indicate speed or mileage, the cable may be broken. Most cables break due to a lack of lubrication or a bend or kink in the housing. The cable also might break when the speedometer head mechanism binds. A jumpy pointer, along with a scraping noise, is often caused by a dry or kinked speedometer cable. The kinked cable rubs on the housing and winds up slowing down the pointer. The cable then unwinds, and the pointer jumps.

To lubricate the cable and check for kinks, the cable will have to be removed from the housing. It is not necessary to remove the housing from the vehicle. From under the dash, disconnect the housing by its fluted nut from the back side of the speedometer head. Prior to removing the cable from the housing, cover the carpet and upholstery, as the common lubricant is graphite which will really make a mess to whatever it touches. Using long nose pliers, pull on the cable while supporting the housing. The cable should come out fairly easily, unless there is a crimp somewhere in the housing, which could be the cause of the problem by itself.

With the cable fully withdrawn and out of the car, inspect the outer surface of the core for flat and shiny areas. These indicate wear areas and you can use their position to approximate the area of the housing that may have an excessive bend or kink. To check for kinks, lay the cable on a flat surface and twist one end with your fingers. If it turns over smoothly, the cable is not kinked. But, if part of the cable flops over as it’s twisted, the cable is kinked and should be replaced.

Before reinstalling the cable back into the housing wipe it down with a clean absorbent cloth and re-lubricate it with a graphite bearing lubricant. Then feed and twist the cable back into the housing. The last 3/8” to 1/4” will require twisting and pushing to engage the square drive at the far end of the cable.

Before re-connecting the cable housing to the back of the speedometer head, put a few drops of lubricant on the wick through the hole in the speedometer head. I had a hard time doing this so I removed the speedometer head from the dash. The speedometer can be removed from the back of the head on a 1957 model, so you do not have to remove the entire head.

doug7740
1955 Thunderbird Blue

 

[doug7740]

According to the Restoration Manual, the speedometer is lubricated on the wick through the hole in the speedometer head for all three years.

doug7740
1955 Thunderbird Blue

 

[Tommyboy]

What is the problem with my speedometer? It will move back and forth when driving around 30 to 50 MPH and then is steady on a speed when it is going 60-70 MPH. There is no noise coming from it (as I would expect if needed grease) just this steady movement at lower speeds?

The speedometer is attached to your transmission by a cable. As the transmission turns the cable turns a gear in the speedometer head. This gear is attached to a round magnet. The magnet is surrounded by a very close fitting metal cup. As the magnet rotates faster its magnetism starts to pull on the metal cup rotating it slightly. The cup is what drives the visible indication (needle, bar or drum) on the speedometer head. A spring attached to the drum does offer some dampening of the metal cup so movement of vehicle won't affect it but mostly is there to return the indicator to zero when the magnet slows or stops.

When you see speedometers start to waver at speed it is usually some interference between the magnet and cup where the two touch pulling the cup and indicator to a higher speed. Then they let loose and indicator drops. This keeps repeating causing the back and forth movement.

You may have mechanical interference (dirt/dust, worn needle bearings) allowing the magnet and cup to touch only during the slower speeds. The first step would be an inspection and cleaning of the unit but this requires dismantling the speedometer. Some recommendations may be a faulty cable between the transmission/speedometer but this would most likely appear as erratic movements of the speedometer over the whole range of speeds and not just at a narrow band.

Hope this helps.

 

[doug7740]

When you see speedometers start to waver at speed it is usually some interference between the magnet and cup where the two touch pulling the cup and indicator to a higher speed. Then they let loose and indicator drops. This keeps repeating causing the back and forth movement.

You may have mechanical interference (dirt/dust, worn needle bearings) allowing the magnet and cup to touch only during the slower speeds. The first step would be an inspection and cleaning of the unit but this requires dismantling the speedometer. Some recommendations may be a faulty cable between the transmission/speedometer but this would most likely appear as erratic movements of the speedometer over the whole range of speeds and not just at a narrow band.

Hope this helps.

I have rebuilt quite a few of these speedometers and I have never seen a jumpy pointer caused by the rotating magnet and metal cup contacting each other. It there was contact between the rotating magnet and the metal cup that would indicate that the bushing was worn.



A jumpy pointer is often caused by a dry or kinked speedometer cable. The kinked cable rubs on the housing and winds up slowing down the pointer, when cable unwinds the pointer jumps.

doug7740
1955 Thunderbird Blue

 

[zeroroadkill]

My cable was fine, I still pulled it and lubed it with no change. I then oiled the wick on the speedo and it stopped jumping !

 

[Ward 57]

Don't forget the oil cup on the distrubutor also.

 

[zeroroadkill]

Don't forget the oil cup on the distrubutor also.

I lube mine every oil change.
Interesting some older generators had an oil cup or bushing oil port but the’55 generator doesn’t seem to have any. Are these sealed bearings? Maybe a new post?

 

[Tracey Brown]

My speedometer reads about 10 mph slow according to my GPS (and the local sheriff) . It has a 312 with an early air cooled FM automatic tranny and I was told the rear axel was changed at some point but I don't know what gear ratio it is. I saw in the parts catalog there are 4 different gears for the cable depending on the combo. Any way to tell which one I have?

Mine is accurate up to about 25 miles an hour, from there on 45= about 35, 60- about 47, 75= 55... so it gets worse the faster you go, the Needle bounces dramatically at anything over 35 mph. I have been using the Speedometer App on my Iphone, Mine is a 3 speed standard with Over Drive. I would be interested in a solution but have not found any on other forums.

 

[hotrodbuilder]

Speedometer bouncing dramatically usually indicates a dry cable. You need to pull inner cable out and clean and lubricate it with speedo cable lube or lubriplate. That may also correct the erroneous reading. If that does not correct the reading, you may need to change the gear at the transmission end.

 

[biddle]

I would be interested in a solution but have not found any on other forums.

As you can see, this was already answered above by @doug7740. I've merged your post with that topic. See above for the solution. Use the Search page for commonly asked questions.