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Speedometer gauge issue
#1372087 Tue Aug 04 2020 08:06 PM
Joined: Jul 2020
Posts: 5
M
Muffin Offline OP
New Guy
Hello,

I just bought a '53 3100, and have been evaluating the few things that need maintenance and repair. One of those is the speedometer: the needle never moves.

I read the forum and unplugged the cable, both at the gauge and by the transmission, hooked it to a driller, and ran it counter-clockwise. I took the cable out, cleaned it, applied grease, put it back in the sheath, ran the driller again. No motion. Do I need to take the gauge apart?

From reading the forum, 12 volt conversion would not affect the way the speedometer works since it is mechanical. So I'm guessing there may be an issue inside the gauge. Thoughts?

Thanks

Re: Speedometer gauge issue
Muffin #1372095 Tue Aug 04 2020 09:05 PM
Joined: Mar 2019
Posts: 1,038
G
Shop Shark
Not sure , and im sure the experts will chime in. But i would undo the cable at the gauge, put truck on jackstands, run it in gear and see if the cable is spinning. That will either eliminate the cable on down or let you know the problem is the gauge if it turning. I wouldnt just start pulling the gauge apart till i was sure thats where the problem is.

Re: Speedometer gauge issue
Muffin #1372097 Tue Aug 04 2020 09:10 PM
Joined: Jul 2000
Posts: 1,041
G
Shop Clutterist
OK, the needle doesn't move. Does the odometer turn?


Gord
----
1954 1/2 ton 235 4 speed
Re: Speedometer gauge issue
Muffin #1372116 Tue Aug 04 2020 10:51 PM
Joined: Aug 2018
Posts: 395
2
Shop Shark
if you spin the back of the speedo with your fingers you should be able to easily make the needle bounce up to 10s - 20 MPH range in a short hop.
if you can't make that needle bounce up with a finger flick that speedo is NG.

the speedo is nothing magical, take apart, clean all the bits, lubricate gently while reassembling.
to re-magnetize the internal magnet use a couple bar N45 magnets from Amazon.com, you can NOT over magnetize the speedo magnet, it is meant to be saturated.
i attached a screen shot of the particular magnet i used to repair some of mine.
checking the speedo with the GPS showed it was as good as new.
-s

Attached Files
Screen Shot 2020-08-04 at 3.46.57 PM.jpg (84.92 KB, 178 downloads)
Re: Speedometer gauge issue
Muffin #1372335 Thu Aug 06 2020 08:39 PM
Joined: Jul 2020
Posts: 5
M
Muffin Offline OP
New Guy
Thank you all for your replies.

@Glenns: I figured that it was easier and quicker to t other drill test to check if whether the issue was on the cable/gauge side or inside the transmission.

@Gord&Fran: I redid the test, only the odometer runs. The needle still won't move.

@ 2ManyTrucks: I'll look into it, that may explain why the odometer works but not the speedometer.

Thanks!

Re: Speedometer gauge issue
Muffin #1372364 Fri Aug 07 2020 12:28 AM
Joined: Mar 2014
Posts: 1,665
J
Shop Shark
In speedometers there is a hairspring which serves to regulate motion and to return the needle to zero when the cable isn't turning, keep the needle as accurate as possible and keep it steady. Be careful with the hairspring as they can be damaged but not easily repaired.


Jon

1952 1/2 ton with 1959 235
T5 with 3.07 rear end
Re: Speedometer gauge issue
Muffin #1372720 Mon Aug 10 2020 01:34 AM
Joined: Jul 2020
Posts: 5
M
Muffin Offline OP
New Guy
Thanks Jon, I ll be sure to be careful.

I took the truck out today and when it rools, the needle stays around 10 or 20mph. If I accelerate, I can see the needle move but towards 10mph or below... This thing is a mystery...

Re: Speedometer gauge issue
Muffin #1372780 Mon Aug 10 2020 04:04 PM
Joined: Mar 2014
Posts: 1,665
J
Shop Shark
Ok, thanks for that. It tells me what I wanted to hear. Your central shaft is stuck and this is common. To fix this you must remove the speedometer from the truck. First remove the two gauge lights and the high beam light. Mark the high beam light with a piece of masking tape so you won't be confused later. Then unscrew the cable and move it aside. Using a 3/8 inch nut driver or socket remove the 4 nuts holding the speedometer in. Set them aside and remove the speedometer. Then carefully remove the stainless (yours may have been painted) collar shroud holding the glass pane in and set it carefully aside. This is a good time to clean your glass if needed. Now there are 4 images below. Please see the first one. Remove the two screws diagonally opposed and set them aside. Carefully remove the speedometer unit. Now please see the second one. The green arrow shows the worm gear that drives the regular gear that drives your odometer. You can reset your odometer to show anything you want, but that is another discussion. Right now, let's make your speedometer work again. Please look at image 3 below. I mentioned the hair spring. The arrow points to it. Please remember not to turn your speedometer in the opposite direction. It won't do that hairspring any good. Ok now for the really important stuff. Get some penetrating oil (you can even use P.T. Barnum Blaster), but if what you have is in a spray can just spray it into some small thing (maybe a beer bottle top) because you only need a little bit and you don't want to spray this anywhere near your speedometer. Using a tiny screwdriver, dip it into the penetrating oil and place a small drop on the three areas shown by arrows in the fourth image below. Then using a light oil (sewing machine oil or something like that) put a drop of oil on the part shown by the middle arrow. Now when you turn your speedometer with your thumb and forefinger (COUNTERCLOCKWISE as you are looking from behind), your needle should bounce happily up to 30mph or so. And if all is well, you're good to go and you can reinstall your speedometer in reverse order of the way you removed it. Good luck.

Attached Files
speedo 1.JPG (37.87 KB, 90 downloads)
speedo 2.jpg (28.65 KB, 92 downloads)
speedo 3.jpg (32 KB, 90 downloads)
speedo 4.jpg (29.25 KB, 90 downloads)

Jon

1952 1/2 ton with 1959 235
T5 with 3.07 rear end
Re: Speedometer gauge issue
Muffin #1372786 Mon Aug 10 2020 04:29 PM
Joined: Jan 2020
Posts: 499
D
Shop Shark
Jon G, Thanks again for the info. When a body shop had my 54-3100 in storage water got into the original like new speedometer and rusted the face. I thought no problem and replaced it with one from LMC. I know it's a small thing but, the original had a kinda modified arrow point. The replacement has just a straight bar on the speed pointer. Is it advisable to try and put the old style on the new unit? Ed


Currently making 1954 3100 better than new
Re: Speedometer gauge issue
Muffin #1372789 Mon Aug 10 2020 04:39 PM
Joined: Mar 2014
Posts: 1,665
J
Shop Shark
You can do that if you want, Ed. I suppose it is all a matter of personal preference. I don't know if anyone would know the difference. ??


Jon

1952 1/2 ton with 1959 235
T5 with 3.07 rear end
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