Need some help with the speedo for my 51 shoebox. I've spun the bushing in the back with my fingers and can get about 5-10 mph. It spins smooth and freely and doesn't seem like anything is binding or stuck. I gave it a little WD-40. I plug it in to the cable and the needle won't move at all, but the odometer works just fine. Any suggestions?
does it work if you leave the cable nut loose? Sometimes the cable pushes too far into the speedo and makes it bind
Next test to try to get at what is going on: Spin it up with an electric tool with an RPM rating. Electric screwdriver is good starting point. Those big sets of chinese screwdriver bits contain square Robertson bits that fit speedo perfectly. If you get proper movement with reasonable speed numbers (1,000 RPM should get you 60, so just divide as needed to see what your rpm tool should show). If a screwdriver gets reasonable results, move to maybe a variable speed drill or such and see what it does. Here's a marginally applicable old speedo post: Here's my speedo repair technique: remove bezel and glass, get speedo out of case. Get a tin can or something that allows you to set the speedo down with face up and secure balance, and study how you are going to hold the thing so neither your fingers nor the liquids to be used can touch the face or odometer. That stuff is VERY delicate and easy to destroy. Near the cable end, on what amounts to the speedo's main bearing, is a tiny brass plug. Get it out--I usually manage to extract them unhurt by threading a tiny machine screw into the cup--and extract the piece of felt within. I then repeatedly flood this lube well with first kroil then WD40 as it frees up, sometimes liquid wrench if I feel something thinner is needed. You want lots of fluid to go in there and then leak out the bottom to dissolve and wash out the petrified lubricant and crud. When the shaft will spin freely by finger twirl--you should be able to get 5-10MPH easily by finger--soak several times with carb cleaner and then brake cleaner to remove all those miracle solvents. When drained and dry, I fillerup with Marvel Mystery Oil, based on my scientific observation that the only real speedo tech I ever saw in action used something that sure looked like MMO. Stuff felt&cap back into hole, well soaked. Let drain, reassemble. The multiple screwdriver tip sets you can get at discount stores contain a Canadian Robertson tip (square) that fits early Ford speedos and allows you to motor them up. You can also do a very rough test based on the supposed RPM of your electric tool, based on the speedo's calibration of 1,000 RPM=60 MPH. Here's a ratio test page: 1. http://www.speedometershop.com/rep-pag.htm
If you sprayed WD40 into the inside of the speedo and not just on the bushing you might have dislodged some debris and it stuck between the speedcup and field plate. Like squirrel said in the first post if the speedometer cable has stretched or is to long, when the nut is tightened it will put pressure on the cup and not let the needle move. The cable should stick out 3/8's of an inch past the ferrule on the speedo end and no more than 1 inch at the transmission end, if it is any longer that could be your trouble and needs to be replaced or shortened at the transmission end. Do you have the speedo with the needle that has a circle on the end that surrounds the mph number?
The cable issue is why it needs to be spun up...to see if head functions. If it does, then something is wrong with the cable. The finger-spin test suggests that head may well be good.
I'll try leaving the cable loose, engaged just enough. I'll also try the Robertson Bit....I actually have one, just never thought to use it to spin up the speedo. When I hooked the cable up for the very first time it made a gawd awful noise. No speedo, but the odometer still worked even then. I quickly unplugged it, (not only for my sanity, but for preserving the Speedo). Basically it was bone dry, that's when I flooded it with WD-40 and spun it with my fingers it spun nice and smooth and the needle moved. I've never taken one apart enough to see whats behind the bronze bushing where the cable plugs into, but everything outside of that appears to be good. Thanks for the help guys....stay tuned. I'll let you know if anything works.
E1956v....Do you have any general schematics for speedo guts?... that visually points out the "speedcup and fieldplate"? ...sorry, I can assume, but just not exactly sure which components those are. Im a sucker for isometric exploded assembly drawings.
Yes!...I do have the needle with the circle on the end that surrounds the number. When I first put my tranny in I had the problem with the cable being too long at the trans end...It made a terrible noise...luckily I figured it out before anything was damaged, but I ended up buying a brand new cable. I know the cable is turning fine...because I drove around the block with it spinning in my fingers to feel it.....and my odometer works.
I don't have any exploded views of the speedo I can pass on, The speedcup has a shaft that the needle is atached to. On your speedo the cup sits inside the field plate the magnet (the shaft that the cable turns) spins inside the speedcup. Check to see if there is any thing stuck between the speedcup and field plate the cup should float free. If you have replaced the cable and housing and length is correct I think the speedo head needs repaired, the speedcup may be broken. I don't know where you live in California but you could call North Hollywood Speedometer or United Speedometer or Palo Alto Speedometer. If you wanted to send it in to me I will check it out and give a estimate no charge, just the shipping you will have to pay to get it to me. Let me know.
Somebody find me the URL for searching Life magazine pictures...there is actually an amazing speedometer innard one in Life in the early '50's!
Update: I unhooked the cable and tried to spin the drive by hand and I got nothing. I know it worked when I had the unit outside of the dash. I am wondering if this is a gravity issue, as I would most likely have been holding the unit in the horizontal position with the face pointing up at me when I spun it by hand outside of the dash. Now that it's in the dash it's oriented vertically. Here's the URL (i keep it in my favorites) http://images.google.com/hosted/life When I typed speedometer, oddly enough, the only picture that came up was a picture of a 49/50 ford dash and speedo....no innards though. If you can find it that'd be awesome. Something is definately up with the head. I'm not too far from Palo Alto...it's about 10 mins from my work. I might go talk to them next week. I'm going to take it back out today and see if I can get a reaction again in the horizontal orientation....i'll actually try in it both orientations outside of the car. Would that lead me to believe there was actually something up with the field plate? Sounds like maybe the magnet is not doing it's job? ....just speculating.
Thanks for the offer e1956v. I may take you up on that if I can't figure it out by doing some more digging.
If you are still getting miles and no speed the head is bad I would go a head and take it in for repair
I made sure and picked up a complete set of dash gagues back when they were reasonable for my '55 DeSoto. After you get by this episode, I'd sure be on the lookout for a backup speedo (and the cable & housing, too) at a swap meet, etc. Also, you can get inside those old ones and clean & lube everything -- even reset the odometer to ZERO, if you want. If you can lay hands on a second speedometer, you can combine unworn parts from both to make one good one. I did it with both Stude & Plymouth. It only takes patience and go SLOW, so you don't forget where everything goes. The guys have already mentioned the electric drill for occasional checks, as needed. You seem to have a very analytical bent, and you've gotten good ideas from the other HAMBers here. So, I don't think I need to wish you good luck, but good luck, anyway! You're headed in the right direction & things should work out fine. Last ditch? Spend th $$$ & get somebody with plenty of experience to give it a pro fix.
Life...googled several ways, found the Life photo specific paged, hit early reader's Guides, looked in Life paper indexes in the December issues. Photo search, I finally realized, NG because it was a drwing by GM...exploded view of a maybe Buick Speedo. Know it's in there, about '50-53, no time to go through the issues. Wonderful both as graphic art and as information if you find it!
The Jalopy Journal
