Speedometer / speedometer drive gear

[Brianfrench65]

I have been fighting with speedometer problems, since I bought this car 18 months ago.

I found the 19 tooth gear with several broken teeth. I removed the broken tooth pieces, and replaced the gear, and I also changed the speedometer. It all worked for 99 miles. I then found the housing (turtle) cracked. I had missed a broken tooth. I replaced the entire assembly, and I put the original speedometer back, and it all worked for 104 miles.

Now I have another broken gear, 3 teeth broken.

The speedometer cable is new, and very well lubricated with graphite. The speedometer works perfect by attaching a drill to the turtle end, running backwards.

What am I missing? Please.

Thank You;

[Tom Wesenberg]

The housings aren't all the same. Try it for fit to the driveshaft with no gasket, and see if it rocks a little. Some guys have stacked gaskets to lift the housing, if it's too tight to the driveshaft gear.

[Mitch//pa]

You may have an issue (to much play) in the drive shaft bearing and sleeve. This allows movement of the drive shaft putting to much pressure on the driven gear and turtle. Sometimes adding gaskets to the turtle (shimming it away) will help eliminate some of the pressure on the gear. Adding gaskets can also cause an issue when the gear drifts away from the turtle assy...

[Brianfrench65]

Originally Posted by Tom Wesenberg

The housings aren't all the same. Try it for fit to the driveshaft with no gasket, and see if it rocks a little. Some guys have stacked gaskets to lift the housing, if it's too tight to the driveshaft gear.

Tom; thank you. I did check the fit, without the gasket, and used a 3/16" square key ( key stock), and there was a bit of slop in the gear. When I put it together, I used 2 gaskets. I filled the housing with 600 W gear oil. The housing was still full of oil, when I took it down.

The speedometer cable has both support clamps in place (chassis over muffler, and firewall).

I am perplexed.

Thank You;

[Terry, NJ]

Is It possible that the worm gear, that's been cut into the driveshaft is some way buggered up and chewing up the gears in the turtles?. Just wondering!
Terry

[Tom Wesenberg]

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I would remove the gear housing and use a screwdriver to push the driveshaft up and down to check for freeplay like Mitch mentioned. I wonder if the gear has too much clearance, and the teeth are riding up on each other.

[Brianfrench65]

Thank you all for your suggestions.

I was just wondering if I should try an 18 tooth gear? It will be a smaller diameter, and less accurate, however better than "0" .

When I bought the car I did count the tooth positions, and there were 19. The housing also had the raised "19" on the casting.

As far as I know, I have a standard drivetrain, and I do have 19" wheels.

Thank You;

[duke36]

I tried the 18 tooth gear in the stock housing for an overdrive set up for a late '31 with 3.78 rear end. The smaller diameter wouldn't engage the driveshaft gear properly even without the gasket but not sure exactly why.
Check other issues as stated by others. Can the driveshaft gear be installed in the reverse position, i.e., rotate 180 deg? Some other posts may have touched on this

[Brianfrench65]

Well.....when I really look at the 19 tooth gears, it looks (to me), that the gear is Bailey engaged, and possibly the gear is riding up on the drive shaft gear. When I push up on the drive shaft gear, it does not seam to move up at all (car in neutral).

Any additional comments are certainly welcomed.

Thank You;

[Brianfrench65]

Second view of the 19 tooth gears. Both had failed.

Thank You;

[Gabalus]

I heard someone have the same problems because he used parts from 4.55 to 1 rear axle and from 3.7 to 1.

[Brianfrench65]

Originally Posted by Tom Wesenberg

I would remove the gear housing and use a screwdriver to push the driveshaft up and down to check for freeplay like Mitch mentioned. I wonder if the gear has too much clearance, and the teeth are riding up on each other.

Tom; after studying the failed gears, I do believe you are correct "and the teeth are riding up on each other".

So.....do I put another new gear in, and assemble without a gasket? A skim of form-a-gasket?

Any suggestions are greatly appreciated.

Thank You;

[duke36]

Brian: attached is a photo I rec'd of the drive gear position, if that helps.Hopefully this matches with yours.

[Brianfrench65]

Duke; yes that's what mine looks like. I just can't seem to keep a gear intact.

[duke36]

How much axial travel in the driveshaft gear ?

[Brianfrench65]

Duke; I can't seem to get any, by pushing up with a screwdriver (transmission in neutral). Maybe a slight movement, but I really can't find any.

Thank You;

[duke36]

Does the gear on the driveshaft slide along it some? Mine slides about 1/4" and am told the turtle and small gear keeps it in position. Perhaps you could jack the rear end and see how the drive shaft gear is behaving without the turtle attached .

[Tom Wesenberg]

I would spin the gear as you slowly lay it against the driveshaft. As soon as you can't spin the gear see how much distance you have to seat the housing. This will be the amount of teeth engagement. Maybe you need a different housing that lets the gear engage more.

[Brianfrench65]

Originally Posted by Tom Wesenberg

I would spin the gear as you slowly lay it against the driveshaft. As soon as you can't spin the gear see how much distance you have to seat the housing. This will be the amount of teeth engagement. Maybe you need a different housing that lets the gear engage more.

Tom; I think that you are correct, however trying 3) different housings, all seem to be the same. I am just about seated, before I feel the gears meshing (using a piece of 3/16" square stoch in the square cable hole). Without any gasket, it still feels like, only slight engagement.

One of the housings I tried, I think is an original.

Thank You;

[Mitch//pa]

I stand by post #3 as a potential cause for your problem

[Brianfrench65]

Originally Posted by Mitch//pa

I stand by post #3 as a potential cause for your problem

Mitch; thank you. I am going to put the rear wheels on jack stands and see what things look like, when the drive shaft turns.

Thank You;

[Brianfrench65]

Not knowing the inner workings of a speedometer, is it possible that the speedometer freezes, or locks up inside, causing the drive gear to stop and break a tooth?

Should I buy a rebuilt speedometer, and try again?

With the rear wheels on jack stands, and a wheel chock under one of the rear wheels, and me wife turning the other wheel, I still do not see any axial movement of ecentric motion from the spiral gear on the drive shaft.

Any suggestions, please.

Thank You;

[Mitch//pa]

A hanging speedo head would easily take out the cable first

[Brianfrench65]

Originally Posted by Mitch//pa

A hanging speedo head would easily take out the cable first

Mitch; I did have a cable break at the drive gear end. It broke the thin aluminum housing, that captures the nut to hold it to the drive gear housing. I was thinking something in the road hit it, but maybe this is leading back to the speedometer head.

The last couple of housings I put on, I used multiple gaskets, thinking I didn't have enough clearance. I think that's why it looks like the drive shaft gear was riding on top of the speedometer drive gear.

I have a rebuilt speedometer and will try this with a new drive gear and 1) gasket.

Thank You Very a Much;

[Brianfrench65]

The broken cable housing end that connects to the drive gear housing (turtle).

[Mitch//pa]

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That takes a heavy trauma to break gears, turtles, and the speedo cable collar..
I still think you have to much movement in the driveshaft bearing... Unfortunately it is a lot of work to replace...

If it was a speedo head issue it would just twist and break the inner cable and not do all the damage that's happening to yours.

[Brianfrench65]

Photo looking up.

[Brianfrench65]

Should the drive shaft, spiral drive gear slide towards the transmission, about 1/4" ?

That's the only movement I can get.

I put a jack with a wood dowel on it, and pressed up on the gear. I used a magnetic base indicator, and saw about 0.003 movement, when I jacked up, and applied pressure.

Thank You. I am perplexed.

[Mitch//pa]

Yes that is normal movement

[Brianfrench65]

I found this picture in my archive photograph's, and I am sure it came from a Ford Barn member, however I cannot find the post.

My question is, is the wire ring shown, supposed to lock into the drive shaft, or does it slide easyley?

Thank You;

[Tom Wesenberg]

The wire ring should snap into a groove in the driveshaft.

[Brianfrench65]

Tom; thank you. It seems like mine is not snapped in, and the existing ring seams to be sprung.

Is safety wire an alternative?

I was thinking that I could do that from the speedometer gear drive hole??

Thank You;

[Bob C]

Originally Posted by Brianfrench65

I found this picture in my archive photograph's, and I am sure it came from a Ford Barn member, however I cannot find the post.

My question is, is the wire ring shown, supposed to lock into the drive shaft, or does it slide easyley?

Thank You;

This is what Tom Endy said about the snap ring.

"Over the years of taking rear axle assemblies apart I have noticed that there is a space, maybe 1\8" between the front of the drive gear and the circular snap ring. I have come to the conclusion that the snap ring is not there to position the drive gear as the driven gear assembly will do that when it is installed. I suspect Henry put it there so that the rear axle assembly could be transported down the assembly line hung up-side-down and the snap ring kept the roller bearing, thrust washer and drive gear from falling out."

Bob

[Brianfrench65]

Bob; that's awesome, thank you very much

Thank You;