The Stovebolt Site Forums The Shop Area General Truck Talk Speedometer needle removal ('51)

My speedometer is busted so I bought a used one that works but its needle is broken off. I'd like to take the needle off the busted speedo and put it on the good one.

Does anyone know how to remove the needle from the shaft?

The way I did it was to grasp the needle and apply a small counter clockwise force while pulling upwards. I found this works every time. To mount it, just push it on.

Did you do anything to hold the shaft?

I was thinking it was just a push-on fit. It would probably work just about as well to wiggle it as you pull but that's a guess since I've not personally taken one off.

When the speedometer is at rest, a counter clockwise force is resisted by the shaft stop. Thus you don't need to do anything with the shaft. I would advise against wiggling it because you might damage the shaft.

Thanks Fred! That's some project you have going there... what a transformation that's going to be!

I'll let you know how it goes with the speedometers. Looks like if I can get the needles off I can just swap out the guts which will save me a few bucks because the busted one already has a new decal.

Lots of work to be done on the dash and I'm itching to get started.

Instrument technicians use a TINY gear puller to remove gauge needles, but carefully prying the needle off usually works. I like to grasp the shaft just below the needle with a pair of bent-nose needlenose pliers, and use a small screwdriver to pry the needle off, using the plier jaws as a fulcrum. Stress on the shaft can damage the bearings it rides on, or possibly change the calibration by distorting the snail-shell spring that returns the speedo to zero.
Jerry

I hope that it helps you with your speedometer project. My project is now on the road now:

http://rides.webshots.com/album/560963159VKsXQO

Right now it is in getting a professional finish.

Thanks Hotrod, that's an excellent idea. I did try to gently get mine off but it didn't just slide off so I figured it would be best to ask first. My main concern was damaging the mechanism by putting too much stress on the shaft and your suggestion addresses exactly that concern.

Truckernix, Man that is a sweet ride... the white color really looks good.

That method of removal makes complete sense to me Jerry and sounds like the safest way. The next step that pops into my mind is the reverse. Can you turn the needle by holding the shaft or cup after you press it back on to calibrate it to zero?

I'm going to be pulling mine out this winter to see if I can stop the little rattle and needle bounce that starts up about 48 or 50mph. Can be an indication of a bad bushing but I'm hoping that just a drop of sewing machine oil on the bushing will solve it. I might not have to pull the needle off but it never hurts to be well informed.

The cable and housing have been out, found to be in good shape, were cleaned and re-lubed with White Lithium. Speedo is perfectly smooth up to the trouble spot.
Denny Graham
Sandwich, IL

Denny, that type of needle bounce is almost always caused by a rough spot in the cable housing that sets up a twist in the cable at a specific speed. I've chased that type of problem repeatedly, and I've found about the only surefire fix is replacing both the inner cable and the housing as a matched pair. Most shops that do big truck tachometer repairs can custom fabricate a speedo cable using whatever threaded ends are appropriate for the old stovebolts. Use your old cable and housing as a pattern.
Jerry

Edit: For calibrating the zero point, I usually install the needle just below the stop pin, and gently lift it over so the return spring holds it lightly against the pin. I suppose the needle could be twisted on the shaft, carefully, if necessary. Just hold the shaft with one plier, and turn the needle with your fingers, or another plier. Those plastic needles can get VERY brittle with age, however, so be very gentle.
Jerry

Is this to say the cables currently marketed are not good?

No, just saying that an old cable housing, no matter how good it looks on the outside, can have rough spots internally. They usually happen on the outside curve of a somewhat sharp bend,where the internal cable rubs the housing. Newer-design cable housings have a slick Teflon liner that reduces the tendency to develop those rough spots.
Jerry

Cool... thanks!

My speedo needle was broken a bit on the end so I purchased a new one. I pulled the old one off but couldn't get the new one to stay on. The very tip off the shaft broke off, apparently, so I still don't know exactly how to repair it.

Ya got a point there Jerry, that could be a possability, even though the cable didn't show any signs of chaffing when I had it out. I'm replacing most everything I can find with new anyway, so a spedo cable taint gonna break me and it just might keep me from having to break into the speedo case.
tks for the idea.

I did a lot of work on antique radios so I've got a pretty good feel for airplane dial needles. I'm well aware of how fragile they can be.
Denny G

For those that may be interested, some may have seen my post a while back but I'll repeat it. I had a bounce in my speedo and figured it was the cable. Put a new cable in my old housing and still the same problem. Next took speedometer to a local shop close by (D&M Restorations) and watched Mike test it. Tested very smooth.(Mike redid it about 7 years ago) So, I bought a new cable AND housing. Still same problem. Took the entire set up back over to Mike and we discovered the NEW cable and the NEW cable with housing had ends that were to small. Mike made me a new cable and I put it in my new housing and the speedometer is once again smooth.
So, to someone who ask is new ones good....beware and have your dial calipers ready.
To someone who said it may be the cable right on...and yes the trucking folks can make you one. They usually have a "spool" of the cable and the dies to make (hammer) the right size ends.

I posted this before but it disappeared:
The speedometer on these AD trucks does not have a stop external to the face. Therefore if you give the needle some gentle counterclockwise persuasion, it works against the internal stop. Also the needles are made of steel, or at least mine were. I have two "practice" speedometers that I honed my technique on.

For checking the head calibration I turned the input shaft at a constant rate of speed using a drill, for a measured amount of time. I then used the odometer readings to calculate what the speed was. My unit checked out perfectly.

Fred

The broken needle I have is made from some sort of plastic... it literally crumbles when touched. The hub is metal but the needle on mine isn't.

I broke the shaft about 1/8" below the button on mine trying to get it off. Then I took pliers to get the piece out and found that it was tapered. Always something new to learn about these old things.

Well, I now have a restored speedometer thanks to the help I got here. I couldn't budge the needle by twisting and pulling and there wasn't enough shaft to grab with any kind of pliers under the needle hub so I just got a small flat screwdriver and began gently applying pressure under the hub in different locations and it soon loosened and came off.

Once I had the needle off I swapped the good guts from the bad housing into the good housing, pressed the good needle on, cleaned the glass, crimped the chrome bezel and I now have a working speedometer.

I did discover that the good needle was an obvious recent replacement, so now I'm going to try to find a source for a replacement needle and rebuild the old one. In my case a ham fisted PO rendered the speedometer useless through clumsy handling... the instrument appears to be fine, just needs some TLC.

Thanks to everyone for helping.

Great thread on speedo needles! My original plastic needle on my '51 is dried and crumbled, so I bought a replacement plastic. I found that the 'hub' onto which the needle assembly crimps simply pulls straight off of the spindle while holding the spndle with needlenose pliers (unless it's not supposed to and I just broke it). However, I must have altered the springworks, because the spindle no longer zeros out.

If you imagine the speedometer as a clock face, there's a physical stop at 9 o'clock. A tab on the dial (back in the housing), rests on the top of this stop at zero mph. When you accelerate, the dial rotates clockwise. The spring tension is such that it returns the needle back to zero by rotating the dial counterclockwise until the tab hits the stop. This is how it's supposed to work.

But on mine, now that I've messed with it, the spring does not always bring the tab back to the stop (i.e., return the needle to the zero mph position). In fact, at one point, the dial would only rotate counterclockwise (i.e., it would return to a stop at 80 mph, and you could rotate it to zero, but it wanted to return to 80 mph). I now have it to where it rotates clockwise on acceleration, but it doesn't always return to zero with tension against the stop.

I wonder if I've broken the spindle loose back in the works.

I know this is a confusing description, but the point is I think I've changed how the spindle rests relative to the spring tension.

Does anybody have any ideas as to what I may have done and how to fix it?

Don't know much about replacing speedometer needles except that mine is broken. ol_red, would you mind Telling us where you found your replacement needles?

Larry

tarheel: you can get the speedo needles from JimCarter. I bought one for my 52 last summer and think it was about 4 bucks.... well, I see they are now 6.75 You can see them in the link below.

http://www.oldchevytrucks.biz/47_55/full.asp?page=163

Well I just reread this whole thread and I still didn't see any definitive instruction on the calibration of the needle. From my vantage point, that needle has to go back on the shaft in exactly the same rotation or the Speedo is going to be off. The only way that it can be properly calibrated is to check it against a known standard and rotate the needle on the shaft till it is in calibration with the dial face.
I’m still mulling over what Fred posted about comparing the speed over distance registered by the odometer, and then doing the math. That sounds like it would work but I’m not sure to what degree of accuracy would come of it. Seems to me that you would have to be able have pretty tight control over the speed that you register to make that work.
The magnet pulls the speedcup, which is biased by a hairspring. The distance the magnet is from the speedcup (determines the slippage) and can effect the calibration but this is pretty much fixed. So that leaves us with the bias adjustment which can cause it to read slow or fast. By winding it tighter by tuning the needle shaft the Speedo would read slow, by not winding it tight enough it would read fast. So this brings us back to the only adjustment that we can do, which is the rotation of the needle on the shaft. So like the calibration of the arms on an analog clock, the needles have to be friction tight and free enough that you can turn them slightly.
It would be interesting to hear how they are checked from someone who works in a real calibration shop.
Also, I haven’t heard from anyone else that has found a taper on the shaft, or was the one in Frank50’s speedo the only one????
Denny Graham
Sandwich, IL