My speedo used to bounced really bad. Lately, it stops bouncing above 30ish mph and just pegs and 90.
I bought a new cable and hooked up just the dash end tonight. Ran the other end with a drill. Still some bounce, much better, but the speedo head makes a decent amount noise.
I figure it’s time for a clean and lube at minimum. Anyone have a procedure for me?
Check out this previous thread on your topic. This reply in particular may help the most.
Originally Posted by 56chev
Your problem sounds just like the problem I had in my 56 210. The needle would start bouncing around and making an awful screeching noise. Here is how I lubed the speedo in my car: (your truck is probably similar)
Remove the speedo assembly from the truck.
Where the cable screws onto the speedo, look for a little brass cup in a hole. Dig out the cup with a pick or small screwdriver.
Inside the hole will be a little piece of felt. Take it out and clean it with a solvent and dry it completely.
Put a few drops of machine oil on the felt piece, and a couple of drops directly into the hole in the speedo. (most folks recommend sewing machine oil for this, I used Hoppe's gun oil. The colorless oil. Not the Number 9 solvent.)
Replace the felt piece in the hole and the little brass cup.
Use a small drop of oil to lube any other moving parts. Wipe off any excess.
Then you can put it all back together and the noise will be gone.
56chev
Lots of great helpful tips in there for the majority of the maladies that affect our AD speedo's.
Just my $.02 worth, but sounds like you have a speedometer "head" that needs some cleaning/lube. There are also several notes about over-tightening the speedo cable connector at the speedometer end that can cause similar grief.
Let us know how this turns out please.
Dan
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
For further "lube" work on the speedo head, check out this video. It isn't for an actual truck speedometer, but the early Chevy speedometer being worked on is similar enough to your needed disassembly and lubrication process. Sorry about the length of the video and the inevitable ads. The meat of the lube process starts after about the 21 minute mark.
I would say have fun getting to this, but getting the speedo cluster out is not a "fun task" in my book.
Don't forget, for safety sake, disconnect your battery before getting under there. Don't want to let any "smoke" out under the dash.
Good luck and hope your knuckles retain most of their skin!
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
Just a suggestion, but try to use the Search The Site tool link.
I did a quick check with the question "How to replace my speedometer needle" and it provide a whole list of links to previous conversations that discuss pretty much anything you need to know on the topic.
Lots of previous knowledge available in there to help you with your question.
Dan
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
That does help. My previous searches didn’t turn up any useful results.
Something that’s not totally clear to me even after reading those threads. The Jim Carter website mentions little tabs that are bent around the back of a cast hub.
The threads I found mostly described securing the shaft/spindle, and just prying the old needle off. In so doing, are we removing said hub along with the chrome outer covering that has the needle?
I haven't actually attempted that, although I do need to eventually as my needle has been broken for some time.
I think sometime in the past year or so, member "JonG" did a long post with extra details on the repairs. I didn't find it in my search, so it may have been more than a year back.
Perhaps he will come back and re-share his wisdom?
Dan
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
I did find an old thread where he detailed replacing the “spindle/shaft.” I didn’t immediately see much about the needle part but may need to look closer.
The needle is friction fit There are special tools to pull it straight up I usually use two screwdrivers to pry it straight up Protect surfaces with tapes If the shaft snaps off then you will need to fix that too I usually crimp the new needle onto its counter mass and press them on together as it’s very difficult to bend the tabs on the needle metal cup after the counter mass is pressed onto the needle shaft.
I use my fingers to press new needles into place No hammering -s
One of the old threads I was reading, mentioned re-magnetizing the speedometer. Is that something that should be done as of preventative medicine while I have things apart? Or only if I have a known issue?
FWIW, once I cleaned and lubed the mechanism, what’s left of the needle stays steady and the works run nearly silent.
Turn the speedo input at 1000rpm should indicate 60mph Remagnetize only if it’s reading low otherwise it’s not going to do anything.
Alternatively, if you set a power drill on its low setting And use an rpm gauge to check the drill speed You can then linearly interpolate or extrapolate the expected mph indication knowing that 1000 rpm is 60mph
Example Drill is spinning at 800 rpm 800/1000x60 = 48 mph -s
Turn the speedo input at 1000rpm should indicate 60mph Remagnetize only if it’s reading low otherwise it’s not going to do anything.
Alternatively, if you set a power drill on its low setting And use an rpm gauge to check the drill speed You can then linearly interpolate or extrapolate the expected mph indication knowing that 1000 rpm is 60mph
Example Drill is spinning at 800 rpm 800/1000x60 = 48 mph -s
I spun the drill at both low and medium speeds, but have no way of knowing how many RPM that is.
I spun the drill at both low and medium speeds, but have no way of knowing how many RPM that is.
You can get a cheap optical tachometer to figure that out. Search Amazon for "optical tachometer handheld".
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
Find a common lp turntable...it will have a turntable with a diameter of around 12 inches...maybe 11. Something like that. It ought to have a rubber edge on it. Most of them did. Hold the "wheel" made by the outside edge of your speedometer as shown below...the spinning part (which should be a diameter of around 3/8") against the turntable (set for 78 rpm speed). Assuming there's not too much internal drag, your speedometer shaft will be spinning at 1000 rpm or very close to it. Good enough to let you know if you're wildly off or reasonably close. I can offer plenty more advanced math but that's as far as I can go quickly this afternoon. Good luck.
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
I downloaded a strobe tachometer app on my iPhone and put a white mark on the drill. The app says medium speed on my drill is 1164 rpm. The speedometer reads roughly 48 mph at that speed. I have no idea how accurate the app is.
I’m gonna borrow my parents turntable after bit and try Jon’s test. But test #1 shows the Speedo is off.
It doesn’t hurt to re magnetize it ever Just put the magnets on as original north south and let it sit overnight
Do I have to take the needle back off to get that far in? I’ve seen the diagram of the poles in the thread I linked earlier. What do you mean by original north and south?
I don't remember about that but offhand I'd say you only need to remove the unit from the case. If you want to know what is north and south, just hold a compass near it. If the needle runs toward the area...you're looking at the south pole there. If it runs away...you're looking at the north pole in that area. Opposites attract. Same with the magnets you have. You can use the compass to mark those as to N or S.
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
Whatever way the magnets want to naturally stick to the poles in the speedo is correct The field is going to re-enforce the magnetism the correct way The goal is to make one side of the spinny part north and the other side south There was a thread where I drew a diagram to explain it Don’t know how to link to it at the moment but assuming you found it Do it like that Also folks said they had good experience magnetizing like in the old science books way Where you stroke the magnet onto the part and drag it off repeatedly in the correct orientation with aligned poles I tired that a bit and then left the magnets affixed to the speedo part overnight and whatever I did worked perfect because my Speedo was dead on accurate the next day when I did a trial run. -s
Since the picture displays are having an issue this morning (can't see right now what your pics included), figured I could at least link your older post back here so when that problem is resolved we can see what you described.
Looking forward to seeing those pics and hoping they are helpful to all reading here.
Dan
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
The needle pulls straight off Then two tiny screws to remove the face plate After that I think it’s maybe only clips and pins but it will be fairly obvious The needle cup and it’s clock spring come out together and just be gentile with them and it should be easy to reassemble after You have to remove a few worm gear drives And get the magnet exposed It’s very doable and it should all go back together as it came apart Do not get any oil or lubricant onto the clock spring or else it will collect dirt and could cause binding of the spring from winding to winding resulting in poor operation. Just try to pay close attention how stuff comes apart to remember how to put it back together There are many junk trucks with usable parts if anything breaks don’t freak out, it can all be found still fairly easily and cheap -s
Whatever way the magnets want to naturally stick to the poles in the speedo is correct The field is going to re-enforce the magnetism the correct way The goal is to make one side of the spinny part north and the other side south There was a thread where I drew a diagram to explain it Don’t know how to link to it at the moment but assuming you found it Do it like that Also folks said they had good experience magnetizing like in the old science books way Where you stroke the magnet onto the part and drag it off repeatedly in the correct orientation with aligned poles I tired that a bit and then left the magnets affixed to the speedo part overnight and whatever I did worked perfect because my Speedo was dead on accurate the next day when I did a trial run. -s
My magnets seemed plenty happy to bridge the two poles either way. Attached picture shows how I have it set up now. The nuts in the middle are shims to span the gap. Let me know if that looks wrong.
The other pic is to illustrate a question I have. Does the hook end attach to the little protrusion I’m pointing at with the toothpick, on the left? Or does it attach to the other apparatus on the right. And if it attaches on the right, to which part of that apparatus?
I’m a bit concerned your magnets maybe too small to generate enough flux to fully saturate the speedo poles. But maybe it will work If your Speedo still reads low when you are done I would suggest larger magnets You can’t go too big, the poles have to reach their saturation point. That and adding the nuts and metal to complete the flux path adds reluctance to the circuit which also reduces available flux. Larger magnets bridged pole to pole is what worked for me. -s
You might be right, but those little magnets are crazy strong. Al kinds of warnings and they come in a child proof bottle.
I wish I would have bought two sets of them to avoid the nut “shims.”
I’ll see what happens and report back. Aside from the magnet strength, are the magnets positioned in a similar way to what you did? I used your drawing to guide the process.
Disassembling down to this point gave me the opportunity to clean and lube several more gears.
For a quick function test before I reassemble and run the cable in a drill again….
I think I will shorten the stack by removing the nuts, and hold the stack in between the two poles, with the stack polarity reversed. It should spin, or at least start to turn.
I wouldn’t reverse the magnet polarity and introduce them to the poles That will immediately start to desaturate the poles in the speedo Just reassemble and do your test If it’s good - great If not - at least it’s not back in the dash -s
The strongest magnets you might find are those removed from old PATA hard disk computer drives. Possibly dead SATA drives, however by the time the SATA scheme took hold it was discovered weaker magnets would suffice.
If this speedometer project goes toes up on you (which I don't think it will) and if you are going to be swapping rear end and transmission anyhow, I am considering making a "look-alike" GPS speedometer (my plan is to make one which will simply bolt in to the stock housing and use a new-style face plate either with or without turn signal indicators). You can see what mine looks like below. It isn't exact, but it is as close as anything I've seen. It uses the old style bulbs (plus an led for high beam) so it will not look different at night. One slight drawback is making the face plate. I will have to enlist some help in writing the CNC program since it will need to use X-Y-Z and not just X-Y (which I can handle).
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
The engineer in me really appreciates your solutions Jon I don’t mean any disrespect I love reading your posts and I do occasionally go down the same path
I worked in tech in Silicon Valley for 17yrs We had many magnets in all sorts of designs It’s a very complicated field (pun intended) Old disk drive magnets are the same bulk strength as the ones I suggested, about an n41 rating, but drive magnets are very specific shapes that are more difficult to work with And as long as the magnets can make the speedo pole reach saturation that’s all that matters
Gps is already on a planned obsolescence schedule Sure other countries are picking it up Pretty much All gps modules support Galileo and glonass now but I like not relying on a satellite Besides, only a good old speedo tells you how fast the tire is spinning when your stuck And it will never go obsolete
I’ve had too many overly complicated solutions fail in my life where the tech changed enough that it was almost a redesign to maintain it I learned that lesson now, keep it simple and serviceable. -s
Reassembled and ran the drill again. Good news is the needle is much steadier. Bad news is that the speed per drill rpm is way worse now. Like, twice as bad.
Wondering what I did wrong. Need stronger magnets? I don’t understand how it could have gotten worse.
Clock spring maybe too tight? Or has oil or lubricant on it? Does the needle have friction on it? When you move it by hand and release it, it should have the elegance of a butterfly and move swiftly but gracefully to home and even bounce a bit with speed as it drops to the 0 peg.
The good news is the magnet poles can always be fixed Maybe time for larger magnets and a video of what it’s doing -s
