DB26

Help With 1926 Speedometer

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Hello everyone,

 

While driving my '26 the other day I noticed the speedometer working rather sporadic. Above 15 MPH or so it will drop down to 0. I made a video of what I found when I removed the speedometer cable. I have bench tested the speedometer and it works fine. 

 

 

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I think you should remove the cable inner to check it for twist.

 

I further think you should bench test the speedo by hand. I believe it has a die-cast body. At 90+ years old it is probably swelling (disintegrating, basically). My Dodge 8 speedo is. This causes the speedo body to tighten up on the cable. Erratic speeds follow, as does a twisted cable inner, which will eventually break.

 

After you have proved these parts to be OK, then it is time to perhaps suspect the speedo drive gear. At the moment, you are lifting it and turning it. It should turn but don't lift it to check. There may be some backlash. I am assuming you have enough oil (not grease) in the gearbox to adequately lubricate the gear?

Edited by Spinneyhill (see edit history)

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Thank you for the thorough response. I just recently added new 600w oil to the transmission and it is at the proper level. I will do some further testing. 

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Just watched your video. If memory is correct, that drive that you were moving with the screwdriver should only move when the transmission is rotating. You may want to pull the drive gear assembly and make sure nothing is stripped, broken or worn in there. 

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I was thinking the same thing. I coundnt image why it would be loose. And the transmission is in 1st gear during the video. So even more of a reason for it to be immovable. 

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I had a couple of spare gears but just took a look at them and both are worn. Into the scrap metal bin!

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Darn. This may be the case with mine.

 

I took the Dodge out for a drive just a few minutes ago and now my speedometer doesn't work at all. I must've finished if off when I took it apart. I'll take the gear out this week and post my results. 

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The easiest way to test your speedometer  is to disconnect the cable from behind the speedo meter. With the rear wheels jacked up, blocked safely , run the engine in gear and see if the cable turns. The drive from the tranny could be  worn. It may be better to check the drive gear in the tranny and take it step by step. Pull the cable out and inspect. Next step would be remove speedo from the dash , hold it in your hand and see if it works while the engine is running in gear. remove  the housing and look for felt covered oil holes. The  parts inside of the speedometer are very delicate. Part with the numbers that shows through the window turns by some kind of magnet connection and floats on an axle which must be oiled and must move, rotate, freely. Spin it by hand and if  working properly it will always come back and rest on zero at the window. If I remember correctly there is a micro adjustment screw . The  " counter" adjusting thumb screw could be suspect for lack of lubrication . If the cable is new it may be fractionally too  long . It will fit but the forward pressure will cause problem.

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Thanks for the advice. I will continue to work on this project this week. 

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Did some more digging tonight. I think maybe the speedo gear is stripped. Here is another video:

 

 

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Your gear looks like it is rotating on an eccentric shaft or bore. Are the teeth on the gear worn or is it the bore on the gear. 

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I'll have to study it a little more.  Does anyone know for certain that the speedometer gear is removeable through the top? 

Edited by DB26 (see edit history)

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Another update for today. I took the a Dodge for a drive a few minutes ago and had the speedometer disconnected, but the cable connected to the transmission. As I was driving, I witnessed the cable turning. I grabbed the end of the cable with my fingers and was able to stop it from rotating with very little effort. 

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I can’t remember if it is a key way drift pin or something else that holds the gear in place but certainly sounds like something is stripped worn or sheared off.

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I can see in your video that the teeth on the gear are stripped 

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Okay then I am putting this one on hold until I can locate a new gear. Thanks everyone! 

Edited by DB26 (see edit history)

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Try to find out why it is like that too. Something has caused it to break or strip or whatever has happened. There may be something else to fix while you are on it.

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