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Technical Speedo Fix? 1939 Transmission to 1928 Model A

Discussion in 'Traditional Hot Rods' started by dicer2000, Jun 4, 2016.

  1. dicer2000
    Joined: May 25, 2016
    Posts: 69

    dicer2000
    Member

    Last edited: Jul 15, 2016
  2. 48-760
    Joined: Dec 15, 2009
    Posts: 139

    48-760
    Member
    from OH

    The speedo cable looks big in diameter. If you take the speedo cable off the speedo turtle (Marked 9-34) take a look at the end of the inner speedo cable and also the end of the turtle. The later turtles used a square drive where the Model A you have may be male round with a key drive. I believe Brattons sells the turtle shaft for round hole with a key slot. P/N 23220 for the speedo cable with the male round end key drive.
     
  3. dicer2000
    Joined: May 25, 2016
    Posts: 69

    dicer2000
    Member

    Thanks 48-760. I pulled it off and it seemed to be correct. However, I'm now wondering if the gear inside the turtle is the correct one to engage with the transmission. I need another open afternoon to check it out. Thanks again
     
  4. alchemy
    Joined: Sep 27, 2002
    Posts: 16,727

    alchemy
    ALLIANCE MEMBER

    I've never heard that the turtles were different between A's and V8's. What year A's used a round cable with a tang?

    And, I think the gear on the driveshaft is the same diameter for all the different turtle ratios, so that's probably not the problem. Is the driveshaft gear positioned correctly front to back?

    Let us know what you discover when you take it apart. Maybe you could drive the car with the top of the cable unhooked from the speedo to make sure you at least have a cable that turns.
     

  5. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,682

    Bruce Lancaster
    Member Emeritus

    Ok...'28--early '30 A's with oval speedo used fat cable with a tang drive, '30-31 used the modern type square drive.
    Other than the hole in driven gear for the 2 types of cable, the driven gears (which come in several tooth counts for various rear gears and tire diameters) and their "turtle" can fit any driveshaft/torque tube '28-48. Trans is irrelevant because the drive is on the torque tube.
    There is only one drive gear...the turtles of different ratios have slightly different axle heights so the diferent gears can mesh properly with the driver. First check here...unscrew speedo end of cable and see if THAT is turning.
    I think only likely failures are broken cable OR the stuff at front of driveshaft being improperly assembled/snap ring left out so gear is adrift.
     
  6. dicer2000
    Joined: May 25, 2016
    Posts: 69

    dicer2000
    Member

    How did anyone restore cars without this forum? This is great -- I will start with your suggestions asap. Thanks guys!
     
  7. 5280A2
    Joined: Sep 8, 2014
    Posts: 127

    5280A2

    Dicer: You have the '28-29 speedo cable which should have the tang drive. Many of the replacement inner cables will slide too far into the speedo drive (so-called turtle) so they will not engage the speedometer even though they are turning. This problem can be cured with a small flat washer under the crimped-on square drive at the speedometer end of the cable. The washer will prevent the inner cable from sliding down too far. You have to pull the inner cable all the way out of the outer sleeve from the speedometer end to install the washer; been there done that!
     
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  8. dicer2000
    Joined: May 25, 2016
    Posts: 69

    dicer2000
    Member

    Just to close the loop, I wanted to write what I found (and thank everyone for their input)...

    I started at the bottom of the car double-checking each item. It turns out it was in the speedo unit itself. It had gotten hard to turn, then the speedo cable eventually stripped the inside of the speedometer. So, I misdiagnosed it at first. The speedometer is off to be fixed. I'll keep you posted on the repair job. I got the name off the HAMB message boards, so I'll let you know if he did a good job.

    Thanks again to everyone.
     
    Hotrodmyk and Flathead Dave like this.
  9. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,682

    Bruce Lancaster
    Member Emeritus

    Here's my screed on de-crudding the main bearing in a speedometer:
    Here's my speedo repair technique: remove bezel and glass, get speedo out of case. Get a tin can or something that allows you to set the speedo down with face up and secure balance, and study how you are going to hold the thing so neither your fingers nor the liquids to be used can touch the face or odometer. That stuff is VERY delicate and easy to destroy.Near the cable end, on what amounts to the speedo's main bearing, is a tiny brass plug. Get it out--I usually manage to extract them unhurt by threading a tiny machine screw into the cup--and extract the piece of felt within.I then repeatedly flood this lube well with first kroil then WD40 as it frees up, sometimes liquid wrench if I feel something thinner is needed. You want lots of fluid to go in there and then leak out the bottom to dissolve and wash out the petrified lubricant and crud.When the shaft will spin freely by finger twirl--you should be able to get 5-10MPH easily by finger--soak several times with carb cleaner and then brake cleaner to remove all those miracle solvents. When drained and dry, I fillerup with Marvel Mystery Oil, based on my scientific observation that the only real speedo tech I ever saw in action used something that sure looked like MMO.The multiple screwdriver tip sets you can get at discount stores contain a Canadian Robertson tip (square) that fits early Ford speedos and allows you to motor them up. You can also do a very rough test based on the supposed RPM of your elecric tool, based on the speedo's calibration of 1,000 RPM=60 MPH.Here's a ratio test page:

    1. http://www.speedometershop.com/rep-pag.htm
     
    razoo lew likes this.
  10. dicer2000
    Joined: May 25, 2016
    Posts: 69

    dicer2000
    Member

    Hi everyone. Thanks for all your comments. I did get the speedo working well w/ a little help. Here are the steps I went through and a little video, just in case someone is facing the same problem.



    Here is what I did based on comments from this post:
    1. Checked the Speedo Drive gear (inside the turtle). It was seated correctly and the speedo cable was engaging well inside it.
    2. Pulled the actual speedo and found it gummed up and the speedo cable was the wrong size. It had the smaller size box end that engages in the speedo (for 1930-31 Round face ). I needed the 28-29 oval faced speedometer cable, so it didn't engage correctly in my speedo. Through HAMB I found someone to work on the Speedo (though I wish I would have tried Bruce's method above first). This guy did a great job, re-decaled the numbers, and replaced the stripped out part. I just mailed it to him and he did everything and mailed it back. It cost $120, which I paid through PayPal.

    Here is the speedo guy. I did it all on email:
    Leonard Nichols Jr
    jrnichols642@yahoo.com

    For the cable fix, I just bought the correct cable from CW Moss. ($30). Once I buttoned it all up, it worked fantastically. I seem to remember my grandpa's speedometer jumping all around. This one is rock-solid as you accelerate.
     
  11. FlatJan
    Joined: Dec 13, 2013
    Posts: 259

    FlatJan

    hi
    i have a question concerning the speedo drive. What is the tread for the bolts?
    thanks
     
  12. 5280A2
    Joined: Sep 8, 2014
    Posts: 127

    5280A2

    1/4-28 (1/4-inch fine)
     
  13. FlatJan
    Joined: Dec 13, 2013
    Posts: 259

    FlatJan

    always great info here, thank you :)
     
  14. FlatJan
    Joined: Dec 13, 2013
    Posts: 259

    FlatJan

    ...i have another question
    What kind of cable do i have to use for a 28 speedo on 40 rear end?
    I guess the early tang style for the speedo but will this be correctly driven by the 40s turtle?
    Or do i need the whole 28 stuff, so turtle cable and speedo on the 40 rear end? And will the turtle work with the late rear end?
    Thank you
     
  15. Cliff Ramsdell
    Joined: Dec 27, 2004
    Posts: 1,266

    Cliff Ramsdell
    Member

    @FlatJan to use the 28 to 30 oval speedometer you will need a 28 to 30 cable and change the drive end in your turtle.

    Cables for oval faced speedometer have a round, flagged end on the drive end and a .124 square end on the speedometer end. The cables for the round faced speedometers and the later, up to 1948 have a .104 square on each end. A mismatch could result in the drive end inside the speedometer to spin.

    On the early Model A turtle just slide the drive shaft out of the housing. On the 30 to 48 ones remove the cup that retains the drive shaft and then pull the shaft out of the housing.

    Swap things around to make what you need and your good to go.

    Cliff Ramsdell
    DF45822F-B905-4AF3-95A0-975252F35C42.jpeg 8E529AC9-812F-4C10-A63D-198EA4E262E8.jpeg E40DCD49-05E5-45B3-A7F6-535E07E30D23.jpeg 9E0E9DCE-D19E-4691-B9F6-9FB8314AF1CD.jpeg 63B2BBC9-D4C4-45EE-BEBA-C40F9C9480A7.jpeg 6651DEC8-C257-4A59-8486-ECC24592DD27.jpeg
     
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  16. dwollam
    Joined: Oct 22, 2012
    Posts: 1,300

    dwollam
    Member

    Model A suppliers like Snyders sell mixed end cables for those that have different year speedos and drives.

    Dave
     
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  17. FlatJan
    Joined: Dec 13, 2013
    Posts: 259

    FlatJan

    Oldmate and Cliff Ramsdell like this.
  18. sdluck
    Joined: Sep 19, 2006
    Posts: 2,702

    sdluck
    Member

    Thank you everybody
     
    Oldmate likes this.

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