Lazy speedometer

[Ricosan]

OK, I hooked the transmission up to the back of the speedometer and checked it to see if the gears would work, the cable would turn about 1 revolution and then lock up. It did the same on the other side.
I took the transmission out. On the bench it will turn freely in either gear position. I put it back on and held it back about 3/16” from snug up against the speedometer and it was still locking up.
Am I possibly missing a part? I just have the transmission and the pin that joins them. I don’t understand why tightening should have any effect on the gears.
Ideas?.

Richard

[glennpm]

Hi Richard,


Boy I don't know. My transmission is difference with speedometer cables in and out of it. Can you take closeup pictures of the speedo connection end of your transmission?


Glenn

[glennpm]

Part #B-38 is called a "key". It would slide into the speedo, part #B-37, end of your unit and the other end would slide into the back of your speedometer. This key would have the same square dimensions as the end of a speedometer cable and you could make one. What do you have?

[Ricosan]

I spoke to John Connelly this afternoon. He said that most of these SW were made for use in a trucks and the were calibrated for such. He wants me to send the transmission to him. I think it’s a good idea. I’m sure he will figure out the problem.
I’ll post an update as soon as I get it back.

Richard

[Ricosan]

Hey Guys,

I got my speedometer transmission back from John Connelly. I installed it and the speedometer now works and will indicate speed…but it’s the wrong speed. At around 45mph, it shows about 10 mph difference in speedometer speed from actual speed. This is the same reading I get when I bypass the transmission at the back of the speedometer.
I’m thinking that the transmission may be hooked up backwards (upside down). I have the actuating arm on the bottom?

It may be my imagination, but it doesn’t seem to change the speedometer speed when I shift into overdrive. I am going to disconnect the arm from the OD shaft and try engaging with my hand.

Richard

[glennpm]

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Hi Richard,

If the speed is identical with the Columbia engaged or not, this tells me that the SW speedometer tranny is doing its job correctly. Your turtle may be the wrong one, explaining the error.

On the attached page from the Green Book, find your rear axle on the top row and then select the column marked "NO. TEETH". These refer to the number of teeth in the turtle. The tooth count is cast with raised characters on the turtle.

[V8COOPMAN]

Originally Posted by Ricosan

It may be my imagination, but it doesn’t seem to change the speedometer speed when I shift into overdrive. I am going to disconnect the arm from the OD shaft and try engaging with my hand.

Richard

Richard.....Unless I am mis-understanding, WHY would the SPEEDOMETER SPEED (vehicle speed) change when you shift into O/D? At the time you shift to O/D, the vehicle is STILL only traveling at the SAME speed as before making the shift.

Coop

.

[glennpm]

It will be the same indicated speed with or without overdrive if the SW tranny is working as it appears to be now.

Glenn

[V8COOPMAN]

Originally Posted by glennpm

It will be the same indicated speed with or without overdrive if the SW tranny is working as it appears to be now.

Glenn

Sooo.....Does that mean I'm correct, or that I'm full of it as usual?

Coop

.

[Ricosan]

OK, I see what you are saying. I don’t know what i was thinking! I need to get the right turtle to register the right speed.
Looking at my turtle, it doesn’t seem to have any numbers stamped on it.
Glenn, for some reason I can’t download that chart here on my iPad. I’ll see if I can on my computer.
Richard

[glennpm]

Originally Posted by V8COOPMAN

Sooo.....Does that mean I'm correct, or that I'm full of it as usual?

Coop

.

Coop gets an A+ :-)
You are correct.

[glennpm]

and here is a jpg of the pdf page.



Just for 1933
Please ignore the yellow highlighting which is for my 32 with 40 rear.

[glennpm]

Turtle for a 21 tooth gear.

[Ricosan]

Here is what I have.

[glennpm]

Yeah, unreadable.

Are you reading 10 MPH high or low at 45 MPH with your software?
Do you know the ratio of your rearend?
Tire sizes original 5.50 X 17"?

You can also unbolt the turtle and count the teeth Richard.

[Kube]

Originally Posted by glennpm

This is one of pictures I posted of mine in your other Columbia thread. Mine is the 37-41 transmission.

This is 1940 +.
Earlier are much different.

[Ricosan]

Glenn, yea 5.50 X 17 and I don’t know what the rear end ratio is. It feels like a 411.
Kube, that’s the exact same transmission as i have.
Richard

[ford38v8]

Originally Posted by Ricosan

Here is what I have.

The number on yours appears to have been obliterated, at least the picture doesn't show it. The only reason to obliterate that number would be if the turtle had been modified to accept a different gear than original to the turtle. Guys have done that because the turtle they need was not available. Remove the turtle and count the gear teeth, simple and quick. Then count the revolutions of the driveshaft to one revolution of an elevated wheel, which will indicate the differential ratio. (One elevated wheel will turn twice the ratio.) With that ratio and tire size, you can determine the correct turtle gear.

[Ricosan]

Good morning ford38V8, I don’t understand how I count the revolutions of the drive shaft inside of the torque tube. I can’t see it rotate. Do I need to remove the transmission cover from the floor?

Richard

[glennpm]

Hi Richard,

You may be able to count the driveshaft rotations by putting a crayon mark on the driveshaft gear through the window that's behind the turtle. You would need a helper for this, one rotating the rear wheel and the other counting the rotations through the turtle window. If you had a split clamshell it would be easier.

Pull the turtle first and count the teeth.

Glenn