Could somebody give me advice concerning my speedometer?
 

Hello everyone...
I have a 1978 F150 that the PO has left sitting for a good period of time. (years)
Since I have started driving the truck, things are starting back to working again a little at the time. The speedometer is the subject of my question.

When I get started driving after the truck has been sitting over night or during my work day, the speedometer will not start to register until I am about 5 or 6 miles away from starting.
I figure there must be something inside the speedometer itself that if maybe a (friction ??) fit where the speedometer cable goes inside the speedometer gauge.

Is there a place I can apply some grease or something that will allow the speedometer to work all the time?

I feel like this problem has to do with the sitting up and MAYBE grease drying out or something..... Any ideas?

Thanks everyone...
Mike

If you are able to remove the instrument cluster and access the cable where it connects, you may be able to put a small amount of white lithium grease in the end to lubricate things. You can also do the same where it connects to the transmission. Pulling the cluster is a lot easier than you think, The hardest part is removing the headlight and wiper knobs and that even isn't that bad. To be honest, new cables are relatively cheap, so if you've gotten that far, it may be worth just installing new one. Hopefully its the cable and not the gauge itself.

10-4...
My concern here was whether the gauge is the problem or the cable....
Gauge lubrication?
And my cable concern..... the end of the cable where it engages the guage......

The reason I think it is the gauge is the odometer works fine. I have watched it constantly to see that it works flawlessly even when the speedometer is not working.

So why would one part of the gauge work fine and the actual speedometer not work?

Mike

Good point...if the odometer works, the speedo should also. I cant speak for Ford instruments because I have never tried to fix one, but I have done 50's buicks and all kinds of jeeps. The gear that the speedometer cable engages also has several others that it spins to turn the odo, speedo, and trip. Those gears seem to always be plastic. If this is the case for ford, maybe the speedometer gear has some teeth broken off so it only works sometimes?

Well..... the funny thing about the way this speedometer works is this.....
The speedometer gauge itself will just plain not work, but the odometer continues to gauge the mileage... then, about 5 miles or so down the road, when it starts working, it will jump from zero to 90 in one quick, smooth motion. Then it will settle down to what I suppose is my correct speed (or close anyway). Then it will work fine until I park and shut down.
That is why I am wondering.... (1). how the speedometer part gets its information from the cable and (2). is there a possibility to lubricate the gauge itself so maybe, it MIGHT come back to life.

Thanks y'all....
Mike

I think you want to use graphite rather than a grease.
If it's like a '92 Mustang GT, the cable spins a bracket with a magnet on each end. The needle is connected to a metal disk. The magnets spin around the disk, causing the disk to rotate in the same direction, which moves a needle. I guess a spring pulls the needle back toward zero when you slow down.

The speedometer operates on a magnetic field, the magnetic field causes the speed cup to rotate and move the needle; there is a hairspring that controls the deflection of the needle - SO there is most likely a build up of surface rust and the needle is not moving freely - I would do a mist spray of Marvel Mystery oil inside the speedometer head.
While you have the cable disconnected from the speedometer head, pull the cable core out of of the housing, curl it up, and soak it in oil; wipe ot off, then put it back in the housing.

Good deal guys....
Thanks so much for the insight!

Mike

I think that what happens is part of the speedometer has weak magnetism. When the parts rotate for a while, the magnetism starts to come back & the speedo work. When it sits for a while, magnetism is lost & we start over. I've gone thru at least 75 gauge clusters in the past 10 years, maybe 5 or 10 have had this problem to varying degrees. Some flat out refuse to work no matter how long you spin them. I use an old cable & a drill to test them.

Your best fix will be to replace the speedometer head with a good one. You can spin the back of the speedometer with your fingers to test it. A good one will move the needle as soon as you spin it. If you let me know if you have a 100 or 85 MPH, & if it has the high beam light in the top of the speedo or not I can check & see if I have a good used one.

I have the 85 MPH speedometer with the high beam indicator in the top (blue light bar just above the 45 MPH line.
Here's hoping you have a good one to sell....
THANKS!!
Mike

https://cimg4.ibsrv.net/gimg/www.for...0748cba370.jpg

Mike,
I have a couple of the ones you need, I want to lube them & run them with a drill for a little while to make sure they are OK. I'll get to that tomorrow when I get home from work. Both move the needle as soon as you spin the back with your fingers.

Whichever one you get will be no charge, other than shipping. A forum member helped me out no charge last year, I'm just passing on the help. I'm sure you will do the same for another Ford truck guy if you have the chance.

We'll work out the details tomorrow.

Thanks Scott......
Your generosity is greatly appreciated!
Yes, I am sure I will accumulate some parts that I can pass on too. I enjoy being around and associating with folks like you.
(I wish the world in general was more like that too!)

Thanks again....
Mike

I had a similar problem years ago on my 79 Bronco. It was a worn out speedometer drive gear in the transfer case. Someone else replaced it for me, so I can't comment on how difficult it was.

Yep, that was my fear at first but the odometer works fine.... Thank the Lord!
I think I am going to take out the cable and lube it. Everything on this old truck is rusted and dried out but right now, everything is still in one piece. Most of the rubber is dried out and the only real damage to my seats is where the sun came in and baked the back of the seat upholstery.

Anyway.... back on subject... I figured since I am attacking things by priority, I might need to know ABOUT how fast I am going.... Otherwise, a speeding ticket might top my list of expenses.

Mike

I could use one too....would be happy to send a few bucks your way. PM me.