Speedo woes

[normanpitkin]

I have replaced the broken cable ,made sure it moves freely and used graphite powder to lubricate it .Made sure the shaft fitted into the transmission properly and also into the speedo .Nothing......what did i do wrong? How can  I test what to do next?

[casper50]

take the end out of the speedometer, jack up the rear end and brace well.  Put it in gear and see if the speedo end is turning.  You don't need to rev it up.

[Los_Control]

I was wondering if could remove the cable from the head of the speedo, then drive around the block and see if cable turned.

Then thought it may be distracting and dangerous ....  nah, everything is safe on the internets

[Reg Evans]

Have you tested the speedo with an electric drill, a short piece of speedo cable, and an electric drill in reverse gear ?

[Don Coatney]

[normanpitkin]

Thank you gentlemen ,this is my task for tomorrow!

[Jerry Roberts]

You can put a very small screwdriver into the speedometer where the cable goes and give it a spin . The needle should move . 

[raystewart]

On our 50 the speedo didn't work when we bought it, I found it was frozen up and replaced it with a used one.  Once I got it out I found a screw that covered a port to lube it, soaked it in PB Blaster for a couple of days and it freed up.  Now I have the original and a spare.   

[rb1949]

I picked up a 1/4 drive bit for drill testing. Taking the unit out is a pain. But you have the old broken cable to use.

[Feudin_Wagon]

Not to thread hijack, but since all the speedometer peeps are here... Any idea why the speedo on a 1950 would read 10-12 mph slow? Does it just need a good lube and cleaning up ya think?

[Los_Control]

13 minutes ago, Feudin_Wagon said:

Any idea why the speedo on a 1950 would read 10-12 mph slow? Does it just need a good lube and cleaning up ya think?

I am sure it needs to be cleaned and lubed, or would not hurt it any. On the back of the speedo where the cable connects, is a port for oiling it.

Just a small hole and cotton or fiber filled inside, imagine you put a few drops in it while doing your routine maintenance  

Would be very difficult to get a oil can under the dash, but sure you can use a can and a tube and make something happen.

I would blame the speedo if the needle was binding and jumping around, would be old grease. But a steady consistent 12 mph off, I would look at tire size or speedometer gear is wrong size from a past transmission swap etc...

[Jerry Roberts]

A Zoom Spout Oiler has a flexable telescoping nozzle to reach those difficult applications . They are often used to oil furnace motor bearings . 

[normanpitkin]

Update ,got a drill to the trans  end and managed to get the speedo up to 60mph ,so no problems that end ,or the cable either .Now what?

[rb1949]

Is the final component to pull out the trans drive gear?

[normanpitkin]

I hope not! Is that all there is left to try?

[Branded]

reply removed, miss read post

Edited January 22, 2017 by Branded

[Branded]

18 hours ago, Los_Control said:

I was wondering if could remove the cable from the head of the speedo, then drive around the block and see if cable turned.

Then thought it may be distracting and dangerous ....  nah, everything is safe on the internets

This would be your next step, you need to verify the trans gear is actually spinning the speedometer cable.

[rb1949]

I hope not! Is that all there is left to try?

 

The trans drive gear just sits in a hole where the cable attaches. Or do the drive thing with another person watching the cable.

 

[Branded]

If I'm reading this correctly, if the cable is disconnected from the transmission and the cable is turned at the  transmission end and the speedometer operates then the problem is inside the transmission. If that's the case it's either the drive gear or driven gear that has failed.

[dale]

I checked on a 1947 ply trns I have and there is a 1 1/16  socket fitting where the cable attaches to the transmission.  You can screw it out if it will come..  mine came out with a box wrench  and the gear will come with..Bad news the gear is steel not plastic..Could also be the little square where the cable goes into the trns could be stripped.

[DJ194950]

5 hours ago, rb1949 said:

I hope not! Is that all there is left to try?

 

The trans drive gear just sits in a hole where the cable attaches. Or do the drive thing with another person watching the cable.

 

Maybe if the other person with gloves on tries to put some resistance  on the speedo drive end as an attempt to stop it.. Why? the cable is driven by a gear in the speedo drive adapter at the trans to the drive gear inside the trans. The gears could be bad- probably not so as stated earlier- or the nut on the drive line flange could be loose as the gear inside the trans is held tight  against rotation by the compression pressure against the rear output bearing by the compression of the rear trans nut.

Going by part experience several years ago and looking now looking at the parts book.

If i am wrong on this I Know someone with more current knowledge will correct me!  Would be the first? mistake I made Today! LOL.

DJ

[DrDoctor]

   Worst case scenario, and VERY rare, but it DOES/DID happen – one of the magnets inside of the speedometer has deteriorated to a degree to make the unit essentially DOA, and if that’s the case, replacement of the speedometer is the only cure. Like I said initially: Worst case scenario, and VERY rare, but it DOES happen. Thx.

[Branded]

30 minutes ago, The Dr's In said:

   Worst case scenario, and VERY rare, but it DOES/DID happen – one of the magnets inside of the speedometer has deteriorated to a degree to make the unit essentially DOA, and if that’s the case, replacement of the speedometer is the only cure. Like I said initially: Worst case scenario, and VERY rare, but it DOES happen. Thx.

True but, the OP stated he hooked up a drill motor on the transmission end of the cable and the speedometer operated. This tells me the speedometer if fine.

[DrDoctor]

 

   Oooops, sorry ‘bout that, I missed that point. Thx.

[raystewart]

In another car we had recently purchased a few years ago I had a non-functioning speedo that drove me nuts.  I could jack up a wheel and watch the cable spin when unhooked from the speedo, hook a cable to the speedo cable and driver it with a drill and the speedo would register.  After repeated attempts I pulled the gear from the trans and found that a previous cable had snapped off in the square drove hole so when you hooked the cable up to the trans it would still spin from friction, but with the speedo hooked up there was too much drag and the cable wouldn't spin.  One of the more maddening things I have run across over the years!